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Children's Health: Spleen and Lymphatic System
The lymphatic system is an extensive drainage network that helps keep bodily fluid levels in balance and defends the body against infections. It is made up of a network of lymphatic vessels that carry lymph — a clear, watery fluid that contains protein molecules, salts, glucose, urea, and other substances — throughout the body.
The spleen, which is located in the upper left part of the abdomen under the ribcage, works as part of the lymphatic system to protect the body, clearing worn out red blood cells and other foreign bodies from the bloodstream to help fight off infection.
About the Spleen and Lymphatic System
One of the lymphatic system's major jobs is to collect extra lymph fluid from body tissues and return it to the blood. This process is crucial because water, proteins, and other substances are continuously leaking out of tiny blood capillaries into the surrounding body tissues. If the lymphatic system didn't drain the excess fluid from the tissues, the lymph fluid would build up in the body's tissues, and they would swell.
The lymphatic system also helps defend the body against germs like viruses, bacteria, and fungi that can cause illnesses. Those germs are filtered out in the lymph nodes, small masses of tissue located along the network of lymph vessels. The nodes house lymphocytes, a type of white blood cell. Some of those lymphocytes make antibodies, special proteins that fight off germs and stop infections from spreading by trapping disease-causing germs and destroying them.
The spleen also helps the body fight infection. The spleen contains lymphocytes and another kind of white blood cell called macrophages, which engulf and destroy bacteria, dead tissue, and foreign matter and remove them from the blood passing through the spleen.
Basic Anatomy
The lymphatic system is a network of very small tubes (or vessels) that drain lymph fluid from all over the body. The major parts of the lymph tissue are located in the bone marrow, spleen, thymus gland, lymph nodes, and the tonsils. The heart, lungs, intestines, liver, and skin also contain lymphatic tissue.
One of the major lymphatic vessels is the thoracic duct, which begins near the lower part of the spine and collects lymph from the pelvis, abdomen, and lower chest. The thoracic duct runs up through the chest and empties into the blood through a large vein near the left side of the neck. The right lymphatic duct is the other major lymphatic vessel and collects lymph from the right side of the neck, chest, and arm, and empties into a large vein near the right side of the neck.
Lymph nodes are round or kidney-shaped, and can be up to 1 inch in diameter. Most of the lymph nodes are found in clusters in the neck, armpit, and groin area. Nodes are also located along the lymphatic pathways in the chest, abdomen, and pelvis, where they filter the blood. Inside the lymph nodes, lymphocytes called T-cells and B-cells help the body fight infection. Lymphatic tissue is also scattered throughout the body in different major organs and in and around the gastrointestinal tract.
The spleen helps control the amount of blood and blood cells that circulate through the body and helps destroy damaged cells.
How A Healthy Lymph System Typically Works
Carrying Away Waste
Lymph fluid drains into lymph capillaries, which are tiny vessels. The fluid is then pushed along when a person breathes or the muscles contract. The lymph capillaries are very thin, and they have many tiny openings that allow gases, water, and nutrients to pass through to the surrounding cells, nourishing them and taking away waste products. When lymph fluid leaks through in this way it is called interstitial fluid.
Lymph vessels collect the interstitial fluid and then return it to the bloodstream by emptying it into large veins in the upper chest, near the neck.
Fighting Infection
Lymph fluid enters the lymph nodes, where macrophages fight off foreign bodies like bacteria, removing them from the bloodstream. After these substances have been filtered out, the lymph fluid leaves the lymph nodes and returns to the veins, where it re-enters the bloodstream.
When a person has an infection, germs collect in the lymph nodes. If the throat is infected, for example, the lymph nodes of the neck may swell. That's why doctors check for swollen lymph nodes (sometimes called swollen "glands" — but they're actually lymph nodes) in the neck when your throat is infected.
Problems of the Lymphatic System
Certain diseases can affect the lymph nodes, the spleen, or the collections of lymphoid tissue in certain areas of the body.
Lymphadenopathy. This is a condition where the lymph nodes become swollen or enlarged, usually because of a nearby infection. Swollen lymph nodes in the neck, for example, can be caused by a throat infection. Once the infection is treated, the swelling usually goes away. If several lymph node groups throughout the body are swollen, that can indicate a more serious disease that needs further investigation by a doctor.
Lymphadenitis. Also called adenitis, this inflammation of the lymph node is caused by an infection of the tissue in the node. The infection can cause the skin overlying the lymph node to swell, redden, and feel warm and tender to the touch. This infection usually affects the lymph nodes in the neck, and it's usually caused by a bacterial infection that can be easily treated with an antibiotic.
Lymphomas. These cancers start in the lymph nodes when lymphocytes undergo changes and start to multiply out of control. The lymph nodes swell, and the cancer cells crowd out healthy cells and may cause tumors (solid growths) in other parts of the body.
Splenomegaly (enlarged spleen). In healthy people, the spleen is usually small enough that it can't be felt when you press on the abdomen. But certain diseases can cause the spleen to swell to several times its normal size. Usually, this is due to a viral infection, such as mononucleosis. But in some cases, more serious diseases such as cancer can cause it to expand. Doctors usually tell someone with an enlarged spleen to avoid contact sports like football for a while because a swollen spleen is vulnerable to rupturing (bursting). And if it ruptures, it can cause a huge amount of blood loss.
Tonsillitis. Tonsillitis is caused by an infection of the tonsils, the lymphoid tissues in the back of the mouth at the top of the throat that normally help to filter out bacteria. When the tonsils are infected, they become swollen and inflamed, and can cause a sore throat, fever, and difficulty swallowing. The infection can also spread to the throat and surrounding areas, causing pain and inflammation. A child with repeated tonsil infections may need to have them removed (a tonsillectomy).
Reviewed by: Steven Dowshen, MD
Children's Health: Skin, Hair, and Nails
About Skin, Hair and Nails
Skin is our largest organ. If the skin of a typical 150-pound (68-kilogram) adult male were stretched out flat, it would cover about 2 square yards (1.7 square meters) and weigh about 9 pounds (4 kilograms). Our skin protects the network of muscles, bones, nerves, blood vessels, and everything else inside our bodies. Our eyelids have the thinnest skin, the soles of our feet the thickest.
Hair is actually a modified type of skin. Hair grows everywhere on the human body except the palms of the hands, soles of the feet, eyelids, and lips. Hair grows more quickly in summer than winter, and more slowly at night than during the day.
Like hair, nails are a type of modified skin. Nails protect the sensitive tips of fingers and toes. Human nails aren't necessary for living, but they do provide support for the tips of the fingers and toes, protect them from injury, and aid in picking up small objects. Without them, we'd have a hard time scratching an itch or untying a knot. Nails can be an indicator of a person's general health, and illness often affects their growth.
Skin Basics
Skin is essential in many ways. It forms a barrier that prevents harmful substances and microorganisms from entering the body. It protects body tissues against injury. It also controls the loss of life-sustaining fluids like blood and water, helps regulate body temperature through perspiration, and protects from the sun's damaging ultraviolet rays.
Without the nerve cells in skin, people couldn't feel warmth, cold, or other sensations. For instance, goosebumps form when the erector pili muscles contract to make hairs on the skin stand up straight when someone is cold or frightened — the blood vessels keep the body from losing heat by narrowing as much as possible and keeping the warm blood away from the skin's surface, offering insulation and protection.
Every square inch of skin contains thousands of cells and hundreds of sweat glands, oil glands, nerve endings, and blood vessels. Skin is made up of three layers: the epidermis, dermis, and the subcutaneous tissue.
The upper layer of our skin, the epidermis, is the tough, protective outer layer. It's about as thick as a sheet of paper over most parts of the body. The epidermis has four layers of cells that are constantly flaking off and being renewed. In these four layers are three special types of cells:
Melanocytes produce melanin, the pigment that gives skin its color. All people have roughly the same number of melanocytes; those of dark-skinned people produce more melanin. Exposure to sunlight increases the production of melanin, which is why people get suntanned or freckled.
Keratinocytes produce keratin, a type of protein that is a basic component of hair, skin, nails, and helps create an intact barrier.
Langerhans cells help protect the body against infection.
Because the cells in the epidermis are completely replaced about every 28 days, cuts and scrapes heal quickly.
Below the epidermis is the next layer of our skin, the dermis, which is made up of blood vessels, nerve endings, and connective tissue. The dermis nourishes the epidermis. Two types of fibers in the dermis — collagen and elastin — help the skin stretch when we bend and reposition itself when we straighten up. Collagen is strong and hard to stretch, and elastin, as its name suggests, is elastic. In older people, some of the elastin-containing fibers degenerate, which is one reason why the skin looks wrinkled.
The dermis also contains a person's sebaceous glands. These glands, which surround and empty into hair follicles and pores, produce the oil sebum that lubricates the skin and hair. Sebaceous glands are found mostly in the skin on the face, upper back, shoulders, and chest.
Most of the time, the sebaceous glands make the right amount of sebum. As a person's body begins to mature and develop during the teenage years, though, hormones stimulate the sebaceous glands to make more sebum. When pores become clogged by too much sebum and too many dead skin cells, this contributes to acne. Later in life, these glands produce less sebum, which contributes to dry skin as people age.
The bottom layer of our skin, the subcutaneous tissue, is made up of connective tissue, sweat glands, blood vessels, and cells that store fat. This layer helps protect the body from blows and other injuries and helps it hold in body heat.
There are two types of sweat glands. The eccrine glands are found everywhere, although they're mostly in the forehead, palms, and soles of the feet. By producing sweat, these glands help regulate body temperature, and waste products are excreted through them.
The apocrine glands develop at puberty and are concentrated in the armpits and pubic region. The sweat from the apocrine glands is thicker than that produced by the eccrine glands. Although this sweat doesn't smell, when it mixes with bacteria on the skin's surface, it can cause body odor. A normal, healthy adult secretes about 1 pint (about half a liter) of sweat daily, but this may be increased by physical activity, fever, or a hot environment.
Hair Basics
The hair on our heads isn't just there for looks. It keeps us warm by preserving heat. The hair in the nose, ears, and around the eyes protects these sensitive areas from dust and other small particles. Eyebrows and eyelashes protect eyes by decreasing the amount of light and particles that go into them. The fine hair that covers the body provides warmth and protects the skin. Hair also cushions the body against injury.
Human hair consists of the hair shaft, which projects from the skin's surface, and the root, a soft thickened bulb at the base of the hair embedded in the skin. The root ends in the hair bulb, which sits in a sac-like pit in the skin called the follicle, from which the hair grows.
At the bottom of the follicle is the papilla, where hair growth actually takes place. The papilla contains an artery that nourishes the root of the hair. As cells multiply and produce keratin to harden the structure, they're pushed up the follicle and through the skin's surface as a shaft of hair. Each hair has three layers: the medulla at the center, which is soft; the cortex, which surrounds the medulla and is the main part of the hair; and the cuticle, the hard outer layer that protects the shaft.
Hair grows by forming new cells at the base of the root. These cells multiply to form a rod of tissue in the skin. The rods of cells move upward through the skin as new cells form beneath them. As they move up, they're cut off from their supply of nourishment and start to form a hard protein called keratin in a process called keratinization. As this process occurs, the hair cells die. The dead cells and keratin form the shaft of the hair.
Each hair grows about ¼ inch (about 6 millimeters) every month and keeps on growing for up to 6 years. The hair then falls out and another grows in its place. The length of a person's hair depends on the length of the growing phase of the follicle. Follicles are active for 2 to 6 years; they rest for about 3 months after that. A person becomes bald if the scalp follicles become inactive and no longer produce new hair. Thick hair grows out of large follicles; narrow follicles produce thin hair.
The color of a person's hair is determined by the amount and distribution of melanin in the cortex of each hair (the same melanin that's found in the epidermis). Hair also contains a yellow-red pigment; people who have blonde or red hair have only a small amount of melanin in their hair. Hair becomes gray when people age because pigment no longer forms.
Nail Basics
Nails grow out of deep folds in the skin of the fingers and toes. As epidermal cells below the nail root move up to the surface of the skin, they increase in number, and those closest to the nail root become flattened and pressed tightly together. Each cell is transformed into a thin plate; these plates are piled in layers to form the nail. As with hair, nails are formed by keratinization. When the nail cells accumulate, the nail is pushed forward.
The skin below the nail is called the matrix. The larger part of the nail, the nail plate, looks pink because of the network of tiny blood vessels in the underlying dermis. The whitish crescent-shaped area at the base of the nail is called the lunula.
Fingernails grow about three or four times as quickly as toenails. Like hair, nails grow more rapidly in summer than in winter. If a nail is torn off, it will regrow if the matrix isn't severely injured. White spots on the nail are sometimes due to temporary changes in growth rate.
Some of the things that can affect the skin, nails, and hair are described below.
Dermatitis
The term dermatitis refers to any inflammation (swelling, itching, and redness) possibly associated with the skin. There are many types of dermatitis, including:
Atopic dermatitis (eczema). It's a common, hereditary dermatitis that causes an itchy rash primarily on the face, trunk, arms, and legs. It commonly develops in infancy, but can also appear in early childhood. It may be associated with allergic diseases such as asthma and seasonal, environmental, and food allergies.
Contact dermatitis. This occurs when the skin comes into contact with an irritating substance or one that the person is allergic or sensitive to. The best-known cause of contact dermatitis is poison ivy, but there are many others, including chemicals found in laundry detergent, cosmetics, and perfumes, and metals like nickel plating on jewelry, belt buckles, and the back of a snap.
Seborrheic dermatitis. This oily rash, which appears on the scalp, face, chest, and back, is related to an overproduction of sebum from the sebaceous glands. This condition is common in infants and adolescents.
Bacterial Skin Infections
Impetigo. Impetigo is a bacterial infection that results in a honey-colored, crusty rash, often on the face near the mouth and nose.
Cellulitis. Cellulitis is an infection of the skin and subcutaneous tissue that typically occurs when bacteria are introduced through a puncture, bite, or other break in the skin. The area with cellulitis is usually warm, tender, and has some redness.
Streptococcal and staphylococcal infections. These two kinds of bacteria are the main causes of cellulitis and impetigo. Certain types of these bacteria are also responsible for distinctive rashes on the skin, including the rashes associated with scarlet fever and toxic shock syndrome.
Fungal Infections of the Skin and Nails
Candidal dermatitis. A warm, moist environment, such as that found in the folds of the skin in the diaper area of infants, is perfect for growth of the yeast Candida. Yeast infections of the skin in older children, teens, and adults are less common.
Tinea infection (ringworm). Ringworm, which isn't a worm at all, is a fungus infection that can affect the skin, nails, or scalp. Tinea fungi can infect the skin and related tissues of the body. The medical name for ringworm of the scalp is tinea capitis; ringworm of the body is called tinea corporis; and ringworm of the nails is called tinea unguium. With tinea corporis, the fungi can cause scaly, ring-like lesions anywhere on the body.
Tinea pedis (athlete's foot). This infection of the feet is caused by the same types of fungi that cause ringworm. Athlete's foot is commonly found in adolescents and is more likely to occur during warm weather.
Other Skin Problems
Parasitic infestations. Parasites (usually tiny insects or worms) can feed on or burrow into the skin, often resulting in an itchy rash. Scabies and lice are examples of parasitic infestations. Both are contagious and can be easily caught from other people.
Viral infections. Many viruses cause characteristic rashes on the skin, including varicella, the virus that causes chickenpox and shingles; herpes simplex, which causes cold sores; human papillomavirus, the virus that causes warts; and a host of others.
Acne (acne vulgaris). Acne is most common in teens. Some degree of acne is seen in 85% of adolescents, and nearly all teens have the occasional pimple, blackhead, or whitehead.
Skin cancer. Skin cancer is rare in children and teens, but good sun protection habits established during these years can help prevent skin cancers such as melanoma (a serious form of skin cancer that can spread to other parts of the body) later in life, especially among fair-skinned people who sunburn easily.
In addition to these diseases and conditions, the skin can be injured in a number of ways. Minor scrapes, cuts, and bruises heal quickly on their own, but other injuries — severe cuts and burns, for example — require medical treatment.
Disorders of the Scalp and Hair
Tinea capitis, a type of ringworm, is a fungal infection that forms a scaly, ring-like lesion in the scalp. It's contagious and common among school-age children.
Alopecia is an area of hair loss. Ringworm is a common cause of temporary alopecia in children. Alopecia can also be caused by tight braiding that pulls on the hair roots (called tension alopecia). Alopecia areata (when hair falls out in round or oval patches on the scalp) is a less common condition that can affect children and teens.
Reviewed by: Patrice Hyde, MD
Children's Health: Mouth and Teeth
A smile is the facial expression that most engages others. With the help of the teeth — which provide structural support for the face muscles — the mouth also forms a frown and other expressions that show on your face.
The mouth also plays a key role in the digestive system, but it does much more than get digestion started. The mouth — especially the teeth, lips, and tongue — is essential for speech. The tongue, which allows us to taste, also helps form words when we speak. The lips that line the outside of the mouth both help hold food in while we chew and pronounce words when we talk.
With the lips and tongue, teeth help form words by controlling air flow out of the mouth. The tongue strikes the teeth as certain sounds are made.
The hardest substances in the body, the teeth are also necessary for chewing (or mastication) — the process by which we tear, cut, and grind food in preparation for swallowing. Chewing allows enzymes and lubricants released in the mouth to further digest food.
Here's how each aspect of the mouth and teeth plays an important role in our daily lives.
Basic Anatomy of the Mouth and Teeth
The entrance to the digestive tract, the mouth is lined with mucous membranes. The membrane-covered roof of the mouth is called the palate. The front part consists of a bony portion called the hard palate, with a fleshy rear part called the soft palate. The hard palate divides the mouth and the nasal passages above. The soft palate forms a curtain between the mouth and the throat, or pharynx, to the rear. The soft palate contains the uvula, the dangling flesh at the back of the mouth. The tonsils are located on either side of the uvula and look like twin pillars holding up the opening to the pharynx.
A bundle of muscles extends from the floor of the mouth to form the tongue. The upper surface of the tongue is covered with tiny bumps called papillae. These contain tiny pores that are our taste buds. Four main kinds of taste buds are found on the tongue — those that sense sweet, salty, sour, and bitter tastes. Three pairs of salivary glands secrete saliva, which contains a digestive enzyme called amylase that starts the breakdown of carbohydrates even before food enters the stomach.
The lips are covered with skin on the outside and with slippery mucous membranes on the inside of the mouth. The major lip muscle, called the orbicularis oris, allows for the lips' mobility. The reddish tint of the lips comes from underlying blood vessels. The inside portion of both lips is connected to the gums.
There are several types of teeth. Incisors are the squarish, sharp-edged teeth in the front of the mouth. There are four on the bottom and four on the top. On either side of the incisors are the sharp canines. The upper canines are sometimes called eyeteeth. Behind the canines are the premolars, or bicuspids. There are two sets, or four premolars, in each jaw.
The molars, situated behind the premolars, have points and grooves. There are 12 molars — three sets in each jaw called the first, second, and third molars. The third molars are the wisdom teeth, thought by some to have evolved thousands of years ago when human diets consisted of mostly raw foods that required extra chewing power. But because they can crowd out the other teeth or cause problems like pain or infection, a dentist might need to remove them.
Human teeth are made up of four different types of tissue: pulp, dentin, enamel, and cementum. The pulp is the innermost portion of the tooth and consists of connective tissue, nerves, and blood vessels, which nourish the tooth. The pulp has two parts — the pulp chamber, which lies in the crown, and the root canal, which is in the root of the tooth. Blood vessels and nerves enter the root through a small hole in its tip and extend through the canal into the pulp chamber.
Dentin surrounds the pulp. A hard yellow substance, it makes up most of the tooth and is as hard as bone. It's the dentin that gives teeth their yellowish tint. Enamel, the hardest tissue in the body, covers the dentin and forms the outermost layer of the crown. It enables the tooth to withstand the pressure of chewing and protects it from harmful bacteria and changes in temperature from hot and cold foods. Both the dentin and pulp extend into the root. A bony layer of cementum covers the outside of the root, under the gum line, and holds the tooth in place within the jawbone. Cementum is also as hard as bone.
Normal Development of the Mouth and Teeth
Humans are diphyodont, meaning that they develop two sets of teeth. The first set of 20 deciduous teeth are also called the milk, primary, temporary, or baby teeth. They begin to develop before birth and begin to fall out when a child is around 6 years old. They're replaced by a set of 32 permanent teeth, which are also called secondary or adult teeth.
Around the 8th week after conception, oval-shaped tooth buds consisting of cells form in the embryo. These buds begin to harden about the 16th week. Although teeth aren't visible at birth, both the primary and permanent teeth are forming below the gums. The crown, or the hard enamel-covered part that's visible in the mouth, develops first. When the crown is formed, the root begins to develop.
Between the ages of 6 months and 1 year, the deciduous teeth begin to push through the gums. This process is called eruption or teething. At this point, the crown is complete and the root is almost fully formed. By the time a child is 3 years old, he or she has a set of 20 deciduous teeth, 10 in the lower and 10 in the upper jaw. Each jaw has four incisors, two canines, and four molars. The molars' purpose is to grind food, and the incisors and canine teeth are used to bite into and tear food.
The primary teeth help the permanent teeth erupt in their normal positions; most of the permanent teeth form close to the roots of the primary teeth. When a primary tooth is preparing to fall out, its root begins to dissolve. This root has completely dissolved by the time the permanent tooth below it is ready to erupt.
Kids start to lose their primary teeth, or baby teeth, at about 6 years old. This begins a phase of permanent tooth development that lasts over the next 15 years, as the jaw steadily grows into its adult form. From ages 6 to 9, the incisors and first molars start to come in. Between ages 10 and 12, the first and second premolars, as well as the canines, erupt. From 11 to 13, the second molars come in. The wisdom teeth (third molars) erupt between the ages of 17 and 21.
Sometimes there isn't room in a person's mouth for all the permanent teeth. If this happens, the wisdom teeth may get stuck, or impacted, beneath the gum and may need to be removed. Overcrowding of the teeth is one of the reasons kids get braces.
What the Mouth and Teeth Do
The first step of digestion involves the mouth and teeth. Food enters the mouth and is immediately broken down into smaller pieces by our teeth. Each type of tooth serves a different function in the chewing process. Incisors cut foods when you bite into them. The sharper and longer canines tear food. The premolars, which are flatter than the canines, grind and mash food. Molars, with their points and grooves, are responsible for the most vigorous chewing. All the while, the tongue helps to push the food up against our teeth.
During chewing salivary glands in the walls and floor of the mouth secrete saliva, which moistens the food and helps break it down even more. Saliva makes it easier to chew and swallow foods (especially dry foods), and it contains enzymes that aid in the digestion of carbohydrates.
Once food has been converted into a soft, moist mass, it's pushed into the throat (or pharynx) at the back of the mouth and is swallowed. When we swallow, the soft palate closes off the nasal passages from the throat to prevent food from entering the nose.
Problems of the Mouth and Teeth
Proper dental care — including a good diet, frequent cleaning of the teeth after eating, and regular dental checkups — is essential to maintaining healthy teeth and avoiding tooth decay and gum disease.
Common mouth and dental diseases and conditions — some of which can be prevented, some of which cannot — are :
Disorders of the Mouth
Aphthous stomatitis (canker sores). A common form of mouth ulcer, canker sores occur in women more often than in men. Although their cause isn't completely understood, mouth injuries, stress, dietary deficiencies, hormonal changes (such as the menstrual cycle), or food allergies can trigger them. They usually appear on the inner surface of the cheeks or lips, under the tongue, on the soft palate, or at the base of the gums. They begin with a tingling or burning sensation followed by a painful sore called an ulcer. Pain subsides in 7 to 10 days, with complete healing usually occurring in 1 to 3 weeks.
Cleft lip and cleft palate are birth defects in which the tissues of the lip and/or mouth don't form properly during fetal development. Children born with these disorders may have trouble feeding immediately after birth. Reconstructive surgery in infancy and sometimes later can repair the anatomical defects, and can prevent or lessen the severity of speech problems later on.
Enteroviral stomatitis is a common childhood infection caused by a family of viruses called the enteroviruses. An important member of this family is coxsackievirus, which causes hand, foot, and mouth disease. Enteroviral stomatitis is marked by small, painful ulcers in the mouth that may decrease a child's desire to eat and drink and put him or her at risk for dehydration.
Herpetic stomatitis (oral herpes). Kids can get a mouth infection with the herpes simplex virus from an adult or another child who has it. The resulting painful, clustered vesicles, or blisters, can make it difficult to drink or eat, which can lead to dehydration, especially in a young child.
Periodontal disease. The gums and bones supporting the teeth are subject to disease. A common periodontal disease is gingivitis — inflammation of the gums characterized by redness, swelling, and sometimes bleeding. The accumulation of tartar (a hardened film of food particles and bacteria that builds up on teeth) usually causes this condition, and it's almost always the result of inadequate brushing and flossing. When gingivitis isn't treated, it can lead to periodontitis, in which the gums loosen around the teeth and pockets of bacteria and pus form, sometimes damaging the supporting bone and causing tooth loss.
Disorders of the Teeth
Cavities and tooth decay. When bacteria and food particles stick to the teeth, plaque forms. The bacteria digest the carbohydrates in the food and produce acid, which dissolves the tooth's enamel and causes a cavity. If the cavity isn't treated, the decay process progresses to involve the dentin. Without treatment, serious infections can occur. The most common ways to treat cavities and more serious tooth decay problems are: filling the cavity; performing root canal therapy, involving the removal of the pulp of a tooth; crowning a tooth with a cap that looks like a tooth made of metal, porcelain, or plastic; or removing or replacing the tooth. A common cause of tooth decay in toddlers is "baby bottle tooth decay," which occurs when a child goes to sleep with a milk or juice bottle in the mouth and the teeth are bathed in sugary liquid for an extended period of time. To avoid tooth decay and cavities, teach your kids good dental habits — including proper tooth-brushing techniques — at an early age.
Impacted wisdom teeth. In many people, the wisdom teeth are unable to erupt normally so they either remain below the jawline or don't grow in properly. Dentists call these teeth impacted. Wisdom teeth usually become impacted because the jaw isn't large enough to accommodate all the teeth that are growing in and the mouth becomes overcrowded. Impacted teeth can damage other teeth or become painful and infected. Dentists can check if a person has impacted wisdom teeth by taking X-rays of the teeth. If the X-rays show there's a chance that impacted teeth may cause problems, the dentist may recommend that the tooth or teeth be extracted.
Malocclusion is the failure of the teeth in the upper and lower jaws to meet properly. Types of malocclusion include overbite, underbite, and crowding. Most conditions can be corrected with braces, which are metal or clear ceramic brackets bonded to the front of each tooth. The wires connecting braces are tightened periodically to force the teeth to move into the correct position.
Children's Health: Metabolism
Metabolism Basics
Our bodies get the energy they need from food through metabolism, the chemical reactions in the body's cells that convert the fuel from food into the energy needed to do everything from moving to thinking to growing.
Specific proteins in the body control the chemical reactions of metabolism, and each chemical reaction is coordinated with other body functions. In fact, thousands of metabolic reactions happen at the same time — all regulated by the body — to keep our cells healthy and working.
Metabolism is a constant process that begins when we're conceived and ends when we die. It is a vital process for all life forms — not just humans. If metabolism stops, a living thing dies.
Here's an example of how the process of metabolism works in humans — and it begins with plants. First, a green plant takes in energy from sunlight. The plant uses this energy and the molecule chlorophyll (which gives plants their green color) to build sugars from water and carbon dioxide in a process known as photosynthesis.
When people and animals eat the plants (or, if they're carnivores, when they eat animals that have eaten the plants), they take in this energy (in the form of sugar), along with other vital cell-building chemicals.
The body's next step is to break the sugar down so that the energy released can be distributed to, and used as fuel by, the body's cells.
Enzymes
After food is eaten, molecules in the digestive system called enzymes break proteins down into amino acids, fats into fatty acids, and carbohydrates into simple sugars (for example, glucose). In addition to sugar, both amino acids and fatty acids can be used as energy sources by the body when needed. These compounds are absorbed into the blood, which transports them to the cells.
After they enter the cells, other enzymes act to speed up or regulate the chemical reactions involved with "metabolizing" these compounds. During these processes, the energy from these compounds can be released for use by the body or stored in body tissues, especially the liver, muscles, and body fat.
In this way, the process of metabolism is really a balancing act involving two kinds of activities that go on at the same time — the building up of body tissues and energy stores and the breaking down of body tissues and energy stores to generate more fuel for body functions:
Anabolism, or constructive metabolism, is all about building and storing: It supports the growth of new cells, the maintenance of body tissues, and the storage of energy for use in the future. During anabolism, small molecules are changed into larger, more complex molecules of carbohydrate, protein, and fat.
Catabolism, or destructive metabolism, is the process that produces the energy required for all activity in the cells. In this process, cells break down large molecules (mostly carbohydrates and fats) to release energy. This energy release provides fuel for anabolism, heats the body, and enables the muscles to contract and the body to move. As complex chemical units are broken down into more simple substances, the waste products released in the process of catabolism are removed from the body through the skin, kidneys, lungs, and intestines.
The Endocrine System
Several of the hormones of the endocrine system are involved in controlling the rate and direction of metabolism. Thyroxine, a hormone produced and released by the thyroid gland, plays a key role in determining how fast or slow the chemical reactions of metabolism proceed in a person's body.
Another gland, the pancreas secretes hormones that help determine whether the body's main metabolic activity at a particular time will be anabolic or catabolic. For example, after eating a meal, usually more anabolic activity occurs because eating increases the level of glucose — the body's most important fuel — in the blood. The pancreas senses this increased level of glucose and releases the hormone insulin, which signals cells to increase their anabolic activities.
Metabolism is a complicated chemical process, so it's not surprising that many people think of it in its simplest sense: as something that influences how easily our bodies gain or lose weight. That's where calories come in. A calorie is a unit that measures how much energy a particular food provides to the body. A chocolate bar has more calories than an apple, so it provides the body with more energy — and sometimes that can be too much of a good thing. Just as a car stores gas in the gas tank until it is needed to fuel the engine, the body stores calories — primarily as fat. If you overfill a car's gas tank, it spills over onto the pavement. Likewise, if a person eats too many calories, they "spill over" in the form of excess body fat.
The number of calories someone burns in a day is affected by how much that person exercises, the amount of fat and muscle in his or her body, and the person's basal metabolic rate (or BMR). BMR is a measure of the rate at which a person's body "burns" energy, in the form of calories, while at rest.
The BMR can play a role in someone's tendency to gain weight. For example, a person with a low BMR (who therefore burns fewer calories while at rest or sleeping) will tend to gain more pounds of body fat over time, compared with a similar-sized person with an average BMR who eats the same amount of food and gets the same amount of exercise.
What Factors Influence BMR?
To a certain extent, BMR is inherited. Sometimes health problems can affect BMR, but people can actually change their BMR in certain ways. For example, exercising more will not only cause a person to burn more calories directly from the extra activity itself, but becoming more physically fit will increase BMR as well.
BMR is also influenced by body composition — people with more muscle and less fat generally have higher BMRs.
Metabolic Disorders
In a broad sense, a metabolic disorder is any disease that is caused by an abnormal chemical reaction in the body's cells. Most disorders involve either abnormal levels of enzymes or hormones or problems with the functioning of those enzymes or hormones.
When the metabolism of body chemicals is blocked or defective, it can cause a buildup of toxic substances in the body or a deficiency of substances needed for normal body function, either of which can lead to serious symptoms.
Some metabolic diseases are inherited. These are called inborn errors of metabolism. When babies are born, they're tested for many of these in a newborn screening test. Many inborn errors of metabolism can lead to serious complications or even death if they're not controlled with diet or medication from an early age.
G6PD deficiency: Glucose-6-phosphate dehydrogenase (G6PD) is just one of the many enzymes that play a role in cell metabolism. G6PD is produced by red blood cells (RBCs) and helps the body metabolize carbohydrates. Without enough normal G6PD to help RBCs handle certain harmful substances, the cells can be damaged or destroyed, leading to hemolytic anemia. In a process called hemolysis, RBCs are destroyed prematurely, and the bone marrow (the soft, spongy part of the bone that produces new blood cells) may not be able to produce enough new red blood cells.
Kids with G6PD deficiency may be pale and tired and have a rapid heartbeat and breathing. They may also have an enlarged spleen or jaundice (yellowing of the skin and eyes). G6PD deficiency is usually treated by stopping medications or treating the illness or infection causing the stress on the RBCs.
Galactosemia: Babies born with this inborn error of metabolism do not have enough galactose, the enzyme that breaks down the sugar in milk, which is produced in the liver. If the liver doesn't produce enough galactose, the enzyme builds up in the blood and can cause serious health problems.
Symptoms usually occur within the first days of life and include vomiting, a swollen liver, and jaundice. If galactosemia is not diagnosed and treated quickly, it can cause liver, eye, kidney, and brain damage.
Hyperthyroidism: This is when an overactive thyroid gland releases too much of the hormone thyroxine, which increases BMR. It causes symptoms such as weight loss, increased heart rate and blood pressure, protruding eyes, and a swelling in the neck from an enlarged thyroid (goiter). The disease may be controlled with medications or through surgery or radiation treatments.
Hypothyroidism: This is when an absent or underactive thyroid (due to a developmental problem or thyroid disease) causes the release of too little of the hormone thyroxine, which lowers BMR.
If not treated, this condition can result in stunted growth and mental retardation in infants and young children. Hypothyroidism slows body processes and causes fatigue, slow heart rate, excessive weight gain, and constipation. Kids and teens with this condition can be treated with oral thyroid hormone.
Phenylketonuria: Also known as PKU, this is caused by a defect in the enzyme that breaks down the amino acid phenylalanine. This amino acid is necessary for normal growth in infants and children and for normal protein production. However, if too much of it builds up in the body, brain tissue is affected and mental retardation occurs.
Early diagnosis and dietary restriction of the amino acid can prevent or lessen the severity of these complications.
Type 1 diabetes mellitus: This occurs when the pancreas doesn't produce and secrete enough insulin. Symptoms of this disease include excessive thirst and urination, hunger, and weight loss. Over the long term, it can cause kidney problems, pain due to nerve damage, blindness, and heart and blood vessel disease.
Kids and teens with type 1 diabetes need to receive regular injections of insulin and control blood sugar levels to reduce the risk of developing complications.
Type 2 diabetes: This occurs when the body can't respond normally to insulin. Symptoms are similar to those of type 1 diabetes. Many kids who develop type 2 diabetes are overweight, and this is thought to play a role in their decreased responsiveness to insulin.
Some can be treated successfully with dietary changes, exercise, and oral medication, but insulin injections are necessary in other cases. Controlling blood sugar levels reduces the risk of developing the same kinds of long-term health problems that occur with type 1 diabetes.
Children's Health: Male Reproductive System
Reproduction
All living things reproduce. Reproduction — the process by which organisms make more organisms like themselves — is one of the things that sets living things apart from nonliving things. But even though the reproductive system is essential to keeping a species alive, unlike other body systems it's not essential to keeping an individual alive.
In the human reproductive process, two kinds of sex cells, or gametes, are involved. The male gamete, or sperm, and the female gamete, the egg or ovum, meet in the female's reproductive system to create a new individual. Both the male and female reproductive systems are essential for reproduction.
Humans, like other organisms, pass certain characteristics of themselves to the next generation through their genes, the special carriers of human traits. The genes parents pass along to their offspring are what make kids similar to others in their family, but they're also what make each child unique. These genes come from the father's sperm and the mother's egg, which are produced by the male and female reproductive systems.
Understanding the male reproductive system, what it does, and the problems that can affect it can help you better understand your son's reproductive health.
About the Male Reproductive System
Most species have two sexes: male and female. Each sex has its own unique reproductive system. They are different in shape and structure, but both are specifically designed to produce, nourish, and transport either the egg or sperm.
Unlike the female, whose sex organs are located entirely within the pelvis, the male has reproductive organs, or genitals, that are both inside and outside the pelvis. The male genitals include:
the testicles
the duct system, which is made up of the epididymis and the vas deferens
the accessory glands, which include the seminal vesicles and prostate gland
the penis
In a guy who has reached sexual maturity, the two testicles, or testes, produce and store millions of tiny sperm cells. The testicles are oval-shaped and grow to be about 2 inches (5 centimeters) in length and 1 inch (3 centimeters) in diameter. The testicles are also part of the endocrine system because they produce hormones, including testosterone. Testosterone is a major part of puberty in boys, and as a guy makes his way through puberty, his testicles produce more and more of it. Testosterone is the hormone that causes boys to develop deeper voices, bigger muscles, and body and facial hair, and it also stimulates the production of sperm.
Alongside the testicles are the epididymis and the vas deferens, which make up the duct system of the male reproductive organs. The vas deferens is a muscular tube that passes upward alongside the testicles and transports the sperm-containing fluid called semen. The epididymis is a set of coiled tubes (one for each testicle) that connects to the vas deferens.
The epididymis and the testicles hang in a pouch-like structure outside the pelvis called the scrotum. This bag of skin helps to regulate the temperature of testicles, which need to be kept cooler than body temperature to produce sperm. The scrotum changes size to maintain the right temperature. When the body is cold, the scrotum shrinks and becomes tighter to hold in body heat. When it's warm, the scrotum becomes larger and more floppy to get rid of extra heat. This happens without a guy ever having to think about it. The brain and the nervous system give the scrotum the cue to change size.
The accessory glands, including the seminal vesicles and the prostate gland, provide fluids that lubricate the duct system and nourish the sperm. The seminal vesicles are sac-like structures attached to the vas deferens to the side of the bladder. The prostate gland, which produces some of the parts of semen, surrounds the ejaculatory ducts at the base of the urethra, just below the bladder. The urethra is the channel that carries the semen to the outside of the body through the penis. The urethra is also part of the urinary system because it is also the channel through which urine passes as it leaves the bladder and exits the body.
The penis is actually made up of two parts: the shaft and the glans. The shaft is the main part of the penis and the glans is the tip (sometimes called the head). At the end of the glans is a small slit or opening, which is where semen and urine exit the body through the urethra. The inside of the penis is made of a spongy tissue that can expand and contract.
All boys are born with a foreskin, a fold of skin at the end of the penis covering the glans. Some boys are circumcised, which means that a doctor or clergy member cuts away the foreskin. Circumcision is usually performed during a baby boy's first few days of life. Although circumcision is not medically necessary, parents who choose to have their children circumcised often do so based on religious beliefs, concerns about hygiene, or cultural or social reasons. Boys who have circumcised penises and those who don't are no different: All penises work and feel the same, regardless of whether the foreskin has been removed.
What the Male Reproductive System Does
The male sex organs work together to produce and release semen into the reproductive system of the female during sexual intercourse. The male reproductive system also produces sex hormones, which help a boy develop into a sexually mature man during puberty.
When a baby boy is born, he has all the parts of his reproductive system in place, but it isn't until puberty that he is able to reproduce. When puberty begins, usually between the ages of 10 and 14, the pituitary gland — which is located near the brain — secretes hormones that stimulate the testicles to produce testosterone. The production of testosterone brings about many physical changes. Although the timing of these changes is different for every guy, the stages of puberty generally follow a set sequence.
During the first stage of male puberty, the scrotum and testes grow larger.
Next, the penis becomes longer, and the seminal vesicles and prostate gland grow.
Hair begins to appear in the pubic area and later it grows on the face and underarms. During this time, a male's voice also deepens.
Boys also undergo a growth spurt during puberty as they reach their adult height and weight.
Sperm
A male who has reached puberty will produce millions of sperm cells every day. Each sperm is extremely small: only 1/600 of an inch (0.05 millimeters long). Sperm develop in the testicles within a system of tiny tubes called the seminiferous tubules. At birth, these tubules contain simple round cells, but during puberty, testosterone and other hormones cause these cells to transform into sperm cells. The cells divide and change until they have a head and short tail, like tadpoles. The head contains genetic material (genes). The sperm use their tails to push themselves into the epididymis, where they complete their development. It takes sperm about 4 to 6 weeks to travel through the epididymis.
The sperm then move to the vas deferens, or sperm duct. The seminal vesicles and prostate gland produce a whitish fluid called seminal fluid, which mixes with sperm to form semen when a male is sexually stimulated. The penis, which usually hangs limp, becomes hard when a male is sexually excited. Tissues in the penis fill with blood and it becomes stiff and erect (an erection). The rigidity of the erect penis makes it easier to insert into the female's vagina during sexual intercourse. When the erect penis is stimulated, muscles around the reproductive organs contract and force the semen through the duct system and urethra. Semen is pushed out of the male's body through his urethra — this process is called ejaculation. Each time a guy ejaculates, it can contain up to 500 million sperm.
When the male ejaculates during intercourse, semen is deposited into the female's vagina. From the vagina the sperm make their way up through the cervix and move through the uterus with help from uterine contractions. If a mature egg is in one of the female's fallopian tubes, a single sperm may penetrate it, and fertilization, or conception, occurs.
This fertilized egg is now called a zygote and contains 46 chromosomes — half from the egg and half from the sperm. The genetic material from the male and female has combined so that a new individual can be created. The zygote divides again and again as it grows in the female's uterus, maturing over the course of the pregnancy into an embryo, a fetus, and finally a newborn baby.
Things That Can Go Wrong With the Male Reproductive System
Boys may sometimes experience reproductive system problems, including:
Disorders of the Scrotum, Testicles, or Epididymis
Conditions affecting the scrotal contents may involve the testicles, epididymis, or the scrotum itself.
Testicular trauma. Even a mild injury to the testicles can cause severe pain, bruising, or swelling. Most testicular injuries occur when the testicles are struck, hit, kicked, or crushed, usually during sports or due to other trauma. Testicular torsion, when one of the testicles twists around, cutting off its blood supply, is also a problem that some teen males experience, although it's not common. Surgery is needed to untwist the cord and save the testicle.
Varicocele. This is a varicose vein (an abnormally swollen vein) in the network of veins that run from the testicles. Varicoceles commonly develop while a boy is going through puberty. A varicocele is usually not harmful, although it can damage the testicle or decrease sperm production. Take your son to see his doctor if he is concerned about changes in his testicles.
Testicular cancer. This is one of the most common cancers in men younger than 40. It occurs when cells in the testicle divide abnormally and form a tumor. Testicular cancer can spread to other parts of the body, but if it's detected early, the cure rate is excellent. Teen boys should be encouraged to learn to perform testicular self-examinations.
Epididymitis is inflammation of the epididymis, the coiled tubes that connect the testes with the vas deferens. It is usually caused by an infection, such as the sexually transmitted disease chlamydia, and results in pain and swelling next to one of the testicles.
Hydrocele. A hydrocele occurs when fluid collects in the membranes surrounding the testes. Hydroceles may cause swelling in the scrotum around the testicle but are generally painless. In some cases, surgery may be needed to correct the condition.
Inguinal hernia. When a portion of the intestines pushes through an abnormal opening or weakening of the abdominal wall and into the groin or scrotum, it is known as an inguinal hernia. The hernia may look like a bulge or swelling in the groin area. It can be corrected with surgery.
Disorders of the Penis
Disorders affecting the penis include:
Inflammation of the penis. Symptoms of penile inflammation include redness, itching, swelling, and pain. Balanitis occurs when the glans (the head of the penis) becomes inflamed. Posthitis is foreskin inflammation, which is usually due to a yeast or bacterial infection.
Hypospadias. This is a disorder in which the urethra opens on the underside of the penis, not at the tip.
Phimosis. This is a tightness of the foreskin of the penis and is common in newborns and young children. It usually resolves itself without treatment. If it interferes with urination, circumcision (removal of the foreskin) may be recommended.
Paraphimosis. This may develop when the foreskin of a boy's uncircumcised penis is retracted (pulled down to expose the glans) and becomes trapped so it can't be returned to the unretracted position. As a result, blood flow to the head of the penis may be impaired, and your son may experience pain and swelling. A doctor may use lubricant to make a small incision so the foreskin can be pulled forward. If that doesn't work, circumcision may be recommended.
Ambiguous genitalia. This occurs when a child is born with genitals that aren't clearly male or female. In most boys born with this disorder, the penis may be very small or nonexistent, but testicular tissue is present. In a small number of cases, the child may have both testicular and ovarian tissue.
Micropenis. This is a disorder in which the penis, although normally formed, is well below the average size, as determined by standard measurements.
If your son has symptoms of a problem with his reproductive system or he has questions about growth and sexual development, talk with your doctor — many problems with the male reproductive system can be treated.
Children's Health: Lungs and Respiratory System
About the Lungs and Respiratory System
Breathing is so vital to life that it happens automatically. Each day, you breathe about 20,000 times, and by the time you're 70 years old, you'll have taken at least 600 million breaths.
All of this breathing couldn't happen without the respiratory system, which includes the nose, throat, voice box, windpipe, and lungs.
At the top of the respiratory system, the nostrils (also called nares) act as the air intake, bringing air into the nose, where it's warmed and humidified. Tiny hairs called cilia protect the nasal passageways and other parts of the respiratory tract, filtering out dust and other particles that enter the nose through the breathed air.
Air can also be taken in through the mouth. These two openings of the airway (the nasal cavity and the mouth) meet at the pharynx, or throat, at the back of the nose and mouth. The pharynx is part of the digestive system as well as the respiratory system because it carries both food and air. At the bottom of the pharynx, this pathway divides in two, one for food (the esophagus, which leads to the stomach) and the other for air. The epiglottis, a small flap of tissue, covers the air-only passage when we swallow, keeping food and liquid from going into the lungs.
The larynx, or voice box, is the uppermost part of the air-only pipe. This short tube contains a pair of vocal cords, which vibrate to make sounds.
The trachea, or windpipe, extends downward from the base of the larynx. It lies partly in the neck and partly in the chest cavity. The walls of the trachea are strengthened by stiff rings of cartilage to keep it open. The trachea is also lined with cilia, which sweep fluids and foreign particles out of the airway so that they stay out of the lungs.
Trachea and Bronchi
At its bottom end, the trachea divides into left and right air tubes called bronchi, which connect to the lungs. Within the lungs, the bronchi branch into smaller bronchi and even smaller tubes called bronchioles. Bronchioles end in tiny air sacs called alveoli, where the exchange of oxygen and carbon dioxide actually takes place. Each lung houses about 300-400 million alveoli.
The lungs also contain elastic tissues that allow them to inflate and deflate without losing shape and are encased by a thin lining called the pleura. This network of alveoli, bronchioles, and bronchi is known as the bronchial tree.
The chest cavity, or thorax, is the airtight box that houses the bronchial tree, lungs, heart, and other structures. The top and sides of the thorax are formed by the ribs and attached muscles, and the bottom is formed by a large muscle called the diaphragm. The chest walls form a protective cage around the lungs and other contents of the chest cavity.
Separating the chest from the abdomen, the diaphragm plays a lead role in breathing. It moves downward when we breathe in, enlarging the chest cavity and pulling air in through the nose or mouth. When we breathe out, the diaphragm moves upward, forcing the chest cavity to get smaller and pushing the gases in the lungs up and out of the nose and mouth.
What the Lungs and Respiratory System Do
The air we breathe is made up of several gases. Oxygen is the most important for keeping us alive because body cells need it for energy and growth. Without oxygen, the body's cells would die.
Carbon dioxide is the waste gas produced when carbon is combined with oxygen as part of the energy-making processes of the body. The lungs and respiratory system allow oxygen in the air to be taken into the body, while also enabling the body to get rid of carbon dioxide in the air breathed out.
Respiration
Respiration is the set of events that results in the exchange of oxygen from the environment and carbon dioxide from the body's cells. The process of taking air into the lungs is inspiration, or inhalation, and the process of breathing it out is expiration, or exhalation.
Air is inhaled through the mouth or through the nose. Cilia lining the nose and other parts of the upper respiratory tract move back and forth, pushing foreign matter that comes in with air (like dust) either toward the nostrils to be expelled or toward the pharynx. The pharynx passes the foreign matter along to the stomach to eventually be eliminated by the body. As air is inhaled, the mucous membranes of the nose and mouth warm and humidify the air before it enters the lungs.
When you breathe in, the diaphragm moves downward toward the abdomen, and the rib muscles pull the ribs upward and outward. In this way, the volume of the chest cavity is increased. Air pressure in the chest cavity and lungs is reduced, and because gas flows from high pressure to low, air from the environment flows through the nose or mouth into the lungs.
In exhalation, the diaphragm moves upward and the chest wall muscles relax, causing the chest cavity to contract. Air pressure in the lungs rises, so air flows from the lungs and up and out of respiratory system through the nose or mouth.
Every few seconds, with each inhalation, air fills a large portion of the millions of alveoli. In a process called diffusion, oxygen moves from the alveoli to the blood through the capillaries (tiny blood vessels) lining the alveolar walls. Once in the bloodstream, oxygen gets picked up by the hemoglobin in red blood cells. This oxygen-rich blood then flows back to the heart, which pumps it through the arteries to oxygen-hungry tissues throughout the body.
In the tiny capillaries of the body tissues, oxygen is freed from the hemoglobin and moves into the cells. Carbon dioxide, which is produced during the process of diffusion, moves out of these cells into the capillaries, where most of it is dissolved in the plasma of the blood. Blood rich in carbon dioxide then returns to the heart via the veins. From the heart, this blood is pumped to the lungs, where carbon dioxide passes into the alveoli to be exhaled.
Problems of the Lungs and Respiratory System
The respiratory system is susceptible to a number of diseases, and the lungs are prone to a wide range of disorders caused by pollutants in the air.
The most common problems of the respiratory system are:
Asthma. More than 20 million people in the United States have asthma, and it's the #1 reason that kids chronically miss school. Asthma is a chronic inflammatory lung disease that causes airways to tighten and narrow. Often triggered by irritants in the air such as cigarette smoke, asthma flares involve contraction of the muscles and swelling of the lining of the tiny airways. The resulting narrowing of the airways prevents air from flowing properly, causing wheezing and difficulty breathing, sometimes to the point of being life-threatening. Management of asthma starts with an asthma management plan, which usually involves avoiding asthma triggers and sometimes taking medications.
Bronchiolitis. Not to be confused with bronchitis, bronchiolitis is an inflammation of the bronchioles, the smallest branches of the bronchial tree. Bronchiolitis affects mostly infants and young children, and can cause wheezing and serious difficulty breathing. It's usually caused by specific viruses in the wintertime, including respiratory syncytial virus (RSV).
Chronic obstructive pulmonary disease (COPD). COPD is a term that describes two lung diseases — emphysema and chronic bronchitis:
Long-term smoking often causes emphysema, and although it seldom affects kids and teens, it can have its roots in the teen and childhood years. Talking to your kids about smoking is a key part of preventing smoking-related diseases. In emphysema, the lungs produce an excessive amount of mucus and the alveoli become damaged. It becomes difficult to breathe and get enough oxygen into the blood.
In bronchitis, a common disease of adults and teens, the membranes lining the larger bronchial tubes become inflamed and an excessive amount of mucus is produced. The person develops a bad cough to get rid of the mucus. Cigarette smoking is a major cause of chronic bronchitis in teens.
Other Conditions
Common cold. Caused by over 200 different viruses that cause inflammation in the upper respiratory tract, the common cold is the most common respiratory infection. Symptoms may include a mild fever, cough, headache, runny nose, sneezing, and sore throat.
Cough. A cough is a symptom of an illness, not an illness itself. There are many different types of cough and many different causes, ranging from not-so-serious to life-threatening. Some of the more common causes affecting kids are the common cold, asthma, sinusitis, seasonal allergies, croup, and pneumonia. Among the most serious causes of cough are tuberculosis (TB) and whooping cough (pertussis).
Cystic fibrosis (CF). Affecting more than 30,000 kids and young adults in the United States, cystic fibrosis is the most common inherited disease affecting the lungs. Affecting primarily the respiratory and digestive systems, CF causes mucus in the body to be abnormally thick and sticky. The mucus can clog the airways in the lungs and make a person more vulnerable to bacterial infections.
Lung cancer. Caused by an abnormal growth of cells in the lungs, lung cancer is a leading cause of death in the United States and is usually caused by smoking cigarettes. It starts in the lining of the bronchi and takes a long time to develop. Symptoms include a persistent cough that may bring up blood, chest pain, hoarseness, and shortness of breath. Radon gas exposure (radon is a gas that occurs in soil and rocks) may also be a cause of lung cancer. Radon is more likely to occur in certain parts of the United States. You can check your home's radon level by purchasing a radon kit at your local home supply or hardware store.
Pneumonia. This inflammation of the lungs usually occurs because of bacterial or viral infection. Pneumonia causes fever and inflammation of lung tissue, and makes breathing difficult because the lungs have to work harder to transfer oxygen into the bloodstream and remove carbon dioxide from the blood. Common causes of pneumonia are influenza and infection with the bacterium Streptococcus pneumoniae.
Pulmonary Hypertension
This condition occurs when the blood pressure in the arteries of the lungs is abnormally high, which means the heart has to work harder to pump blood against the high pressure. Pulmonary hypertension may occur in children because of a heart defect present at birth or because of a health condition such as HIV infection.
Respiratory Diseases of Newborns
Several respiratory conditions can affect a newborn baby just starting to breathe for the first time. Premature babies are at increased risk for conditions such as:
Respiratory distress syndrome of the newborn. Babies born prematurely may not have enough surfactant in the lungs. Surfactant helps to keep the baby's alveoli open; without surfactant, the lungs collapse and the baby is unable to breathe.
Apnea of prematurity (AOP). Apnea is a medical term that means someone has stopped breathing. Apnea of prematurity (AOP) is a condition in which premature infants stop breathing for 15 to 20 seconds during sleep. Apnea of prematurity generally occurs after 2 days of life and up to a week of life. The lower the infant's weight and level of prematurity at birth, the more likely the baby is to have AOP spells.
Bronchopulmonary dysplasia (BPD). BDP involves abnormal development of lung tissue. Sometimes called chronic lung disease or CLD, it's a disease in infants characterized by inflammation and scarring in the lungs. It develops most often in premature babies who are born with underdeveloped lungs.
Meconium aspiration. Meconium aspiration occurs when a newborn inhales (aspirates) a mixture of meconium (baby's first feces, ordinarily passed after birth) and amniotic fluid during labor and delivery. The inhaled meconium can cause a partial or complete blockage of the baby's airways.
Additional Conditions
Persistent pulmonary hypertension of the newborn (PPHN). In the uterus, a baby's circulation bypasses the lungs. Normally, when a baby is born and begins to breathe air, his or her body quickly adapts and begins the process of respiration. PPHN occurs when a baby's body doesn't make the normal transition from fetal circulation to newborn circulation. This condition can cause symptoms such as rapid breathing, rapid heart rate, respiratory distress, and cyanosis (blue-tinged skin).
Transient tachypnea of the newborn (TTN). Rapid breathing in a full-term newborn (more than 60 breaths a minute) is called transient tachypnea.
Although some respiratory diseases can't be prevented, many chronic lung and respiratory illnesses can be prevented by avoiding smoking, staying away from pollutants and irritants, washing hands often to avoid infection, and getting regular medical checkups.
Children's Health: Kidneys and Urinary Tract
The Importance of the Kidneys and Urinary Tract
Our bodies produce several kinds of wastes, including sweat, carbon dioxide gas, feces (stool), and urine. These wastes exit the body in different ways. Sweat is released through pores in the skin. Water vapor and carbon dioxide are exhaled from the lungs. And undigested food materials are formed into feces in the intestines and excreted from the body as solid waste in bowel movements.
Urine, which is produced by the kidneys, contains the byproducts of metabolism — salts, toxins, and water — that end up in the blood. The kidneys and urinary tract (which includes the kidneys, ureters, bladder, and urethra) filter and eliminate these waste substances from our blood. Without the kidneys, waste products and toxins would soon build up in the blood to dangerous levels.
In addition to eliminating wastes, the kidneys and urinary tract also regulate many important body functions. For example, the kidneys monitor and maintain the body's balance of water, ensuring that our tissues receive enough water to function properly and be healthy.
When doctors take a urine sample, the results reveal how well the kidneys are working. For example, blood, protein, or white blood cells in the urine may indicate injury, inflammation, or infection of the kidneys, and glucose in the urine may be an indication of diabetes.
What They Do
Although the two kidneys work together to perform many vital functions, people can live a normal, healthy life with just one kidney. In fact, some people are born with just one of these bean-shaped organs. If one kidney is removed, the remaining one will enlarge within a few months to take over the role of filtering blood on its own.
Every minute, more than 1 quart (about 1 liter) of blood goes to the kidneys. About one fifth of the blood pumped from the heart goes to the kidneys at any one time.
In addition to filtering blood, producing urine, and ensuring that body tissues receive enough water, the kidneys also regulate blood pressure and the level of vital salts in the blood. By regulating salt levels through production of an enzyme called renin (as well as other substances), the kidneys ensure that blood pressure is regulated.
The kidneys also secrete the hormone erythropoietin, which stimulates and controls red blood cell production (red blood cells carry oxygen throughout the body). In addition, the kidneys help regulate the acid-base balance (or the pH) of the blood and body fluids, which is necessary for the body to function normally.
How They Work
The kidneys are located just under the ribcage in the back, one on each side. The right kidney is located below the liver, so it's a little lower than the left one. Each adult kidney is about the size of a fist. Each has an outer layer called the cortex, which contains the filtering units.
The center part of the kidney, the medulla has 10 to 15 fan-shaped structures called pyramids. These drain urine into cup-shaped tubes called calyxes. A layer of fat surrounds the kidneys to cushion and help hold them in place.
Here's how the kidneys filter blood: Blood travels to each kidney through the renal artery, which enters the kidney at the hilus, the indentation in the kidney that gives it its bean shape. As it enters the cortex, the artery branches to envelope the nephrons — 1 million tiny filtering units in each kidney that remove the harmful substances from the blood.
Each of the nephrons contain a filter called the glomerulus, which contains a network of tiny blood vessels known as capillaries. The fluid filtered from the blood by the glomerulus then travels down a tiny tube-like structure called a tubule, which adjusts the level of salts, water, and wastes that are excreted in the urine.
Filtered blood leaves the kidney through the renal vein and flows back to the heart.
The continuous blood supply entering and leaving the kidneys gives the kidneys their dark red color. While the blood is in the kidneys, water and some of the other blood components (such as acids, glucose, and other nutrients) are reabsorbed back into the bloodstream. Left behind is urine. Urine is a concentrated solution of waste material containing water, urea, a waste product that forms when proteins are broken down), salts, amino acids, byproducts of bile from the liver, ammonia, and any substances that cannot be reabsorbed into the blood. Urine also contains urochrome, a pigmented blood product that gives urine its yellowish color.
The renal pelvis, located near the hilus, collects the urine flowing from the calyxes. From the renal pelvis, urine is transported out of the kidneys through the ureters, tubes that carry the urine out of each kidney to be stored in the urinary bladder — a muscular collection sac in the lower abdomen.
The bladder expands as it fills and can hold about 2 cups (half a liter) of urine at any given time (an average adult produces about 6 cups, or 1½ liters, of urine per day). An adult needs to produce and excrete at least one third of this amount in order to adequately clear waste products from the body. Producing too much or not enough urine may indicate illness.
When the bladder is full, nerve endings in its wall send impulses to the brain. When a person is ready to urinate, the bladder walls contract and the sphincter (a ring-like muscle that guards the exit from the bladder to the urethra) relaxes. The urine is ejected from the bladder and out of the body through the urethra, another tube-like structure. The male urethra ends at the tip of the penis; the female urethra ends just above the vaginal opening.
Problems of the Kidneys and Urinary Tract
Like other systems in the body, the entire urinary tract is subject to diseases and disorders.
In kids, the more common problems include:
Congenital problems of the urinary tract. As a fetus develops in the womb, any part of the urinary tract can grow to an abnormal size or in an abnormal shape or position. One common congenital abnormality (an abnormality that exists at birth) is duplication of the ureters, in which a kidney has two ureters coming from it instead of one. This defect occurs in about 1 out of every 125 births and can cause the kidney to develop problems with repeated infections and scarring over time.
Another congenital problem is horseshoe kidney, where the two kidneys are fused (connected) into one arched kidney that usually functions normally, but is more prone to develop problems later in life. This condition is found in 1 out of every 500 births.
Glomerulonephritis is an inflammation of the glomeruli, the parts of the filtering units (nephrons) of the kidney that contain a network of capillaries (tiny blood vessels). The most common form is post-streptococcal glomerulonephritis, which usually occurs in young children following a case of strep throat. Most kids with this type of nephritis recover fully, but a few can have permanent kidney damage that eventually requires dialysis or a kidney transplant.
High blood pressure (hypertension) can result when the kidneys are impaired by disease. The kidneys control blood pressure by regulating the amount of salt in the body and by producing the enzyme renin that, along with other substances, controls the constriction of muscle cells in the walls of the blood vessels.
Kidney (renal) failure can be acute (sudden) or chronic (occurring over time and usually long lasting or permanent). In either form of kidney failure, the kidneys slow down or stop filtering blood effectively, causing waste products and toxic substances to build up in the blood.
Acute kidney failure may be due to many things, including a bacterial infection, injury, shock, heart failure, poisoning, or drug overdose. Treatment includes correcting the problem that led to the failure and sometimes requires surgery or dialysis. Dialysis involves using a machine or other artificial device to remove the excess salts and water and other wastes from the body when the kidneys are unable to perform this function.
Chronic kidney failure involves a deterioration of kidney function over time. In children, it can result from acute kidney failure that fails to improve, birth defects of the kidney, chronic kidney diseases, repeated kidney infections, or chronic severe high blood pressure. If diagnosed early, chronic kidney failure in children can be treated but usually not reversed. The child will usually require a kidney transplant at some point in the future.
Kidney stones (or nephrolithiasis) result from the buildup of crystallized salts and minerals such as calcium in the urinary tract. Stones (also called calculi) can also form after an infection. If kidney stones are large enough to block the kidney or ureter, they can cause severe abdominal pain. But the stones usually pass through the urinary tract on their own. In some cases, they may need to be removed surgically.
Nephritis is any inflammation of the kidney. It can be caused by infection, medications, an autoimmune disease (such as lupus), or it may be idiopathic (which means the exact cause may not be known or understood). Nephritis is generally detected by protein and blood in the urine.
Nephrotic syndrome is a type of kidney disease that leads to loss of protein in the urine and swelling of the face (often the eyes) or body (often around the genitals). It is most common in children younger than 6 years old and is more prevalent in boys. Nephrotic syndrome is often treated with steroids.
Urinary tract infections (UTIs) are usually caused by intestinal bacteria, such as E. coli, normally found in feces. These bacteria can cause infections anywhere in the urinary tract, including the kidneys. Most UTIs occur in the lower urinary tract, in the bladder and urethra. UTIs occur in both boys and girls. However, uncircumcised males are about 3 to 12 times more likely than circumcised males to develop a UTI before age 1. Although uncircumcised males are about 3 to 12 times more likely than circumcised males to develop a UTI before age 1, most experts don't believe that this is a strong enough reason to recommend routine circumcision for boys. In school-age children, girls are more likely to develop UTIs than boys; this may be because girls have shorter urethras than boys.
Vesicoureteral reflux (VUR) is a condition in which urine abnormally flows backward (or refluxes) from the bladder into the ureters. It may even reach the kidneys, where infection and scarring can occur over time. VUR occurs in 1% of children and tends to run in families. It's often detected after a young child has a first urinary tract infection. Most kids outgrow mild forms of VUR, but some can develop permanent kidney damage and kidney failure later in life.
Wilms' tumor is the most common kidney cancer occurring in children. It is diagnosed most commonly between 2 and 5 years of age and affects males and females equally.
Children's Health: Immune System
The immune system, which is made up of special cells, proteins, tissues, and organs, defends people against germs and microorganisms every day. In most cases, the immune system does a great job of keeping people healthy and preventing infections. But sometimes problems with the immune system can lead to illness and infection.
About the Immune System
The immune system is the body's defense against infectious organisms and other invaders. Through a series of steps called the immune response, the immune system attacks organisms and substances that invade body systems and cause disease.
The immune system is made up of a network of cells, tissues, and organs that work together to protect the body. The cells involved are white blood cells, or leukocytes, which come in two basic types that combine to seek out and destroy disease-causing organisms or substances.
Leukocytes are produced or stored in many locations in the body, including the thymus, spleen, and bone marrow. For this reason, they're called the lymphoid organs. There are also clumps of lymphoid tissue throughout the body, primarily as lymph nodes, that house the leukocytes.
The leukocytes circulate through the body between the organs and nodes via lymphatic vessels and blood vessels. In this way, the immune system works in a coordinated manner to monitor the body for germs or substances that might cause problems.
The two basic types of leukocytes are:
phagocytes, cells that chew up invading organisms
lymphocytes, cells that allow the body to remember and recognize previous invaders and help the body destroy them
A number of different cells are considered phagocytes. The most common type is the neutrophil, which primarily fights bacteria. If doctors are worried about a bacterial infection, they might order a blood test to see if a patient has an increased number of neutrophils triggered by the infection. Other types of phagocytes have their own jobs to make sure that the body responds appropriately to a specific type of invader.
The two kinds of lymphocytes are B lymphocytes and T lymphocytes. Lymphocytes start out in the bone marrow and either stay there and mature into B cells, or they leave for the thymus gland, where they mature into T cells. B lymphocytes and T lymphocytes have separate functions: B lymphocytes are like the body's military intelligence system, seeking out their targets and sending defenses to lock onto them. T cells are like the soldiers, destroying the invaders that the intelligence system has identified.
Here's how it works:
When antigens (foreign substances that invade the body) are detected, several types of cells work together to recognize them and respond. These cells trigger the B lymphocytes to produce antibodies, specialized proteins that lock onto specific antigens.
Once produced, these antibodies continue to exist in a person's body, so that if the same antigen is presented to the immune system again, the antibodies are already there to do their job. So if someone gets sick with a certain disease, like chickenpox, that person typically doesn't get sick from it again.
This is also how immunizations prevent certain diseases. An immunization introduces the body to an antigen in a way that doesn't make someone sick, but does allow the body to produce antibodies that will then protect the person from future attack by the germ or substance that produces that particular disease.
Although antibodies can recognize an antigen and lock onto it, they are not capable of destroying it without help. That's the job of the T cells, which are part of the system that destroys antigens that have been tagged by antibodies or cells that have been infected or somehow changed. (Some T cells are actually called "killer cells.") T cells also are involved in helping signal other cells (like phagocytes) to do their jobs.
Antibodies also can neutralize toxins (poisonous or damaging substances) produced by different organisms. Lastly, antibodies can activate a group of proteins called complement that are also part of the immune system. Complement assists in killing bacteria, viruses, or infected cells.
All of these specialized cells and parts of the immune system offer the body protection against disease. This protection is called immunity.
Immunity
Humans have three types of immunity — innate, adaptive, and passive:
Innate Immunity
Everyone is born with innate (or natural) immunity, a type of general protection. Many of the germs that affect other species don't harm us. For example, the viruses that cause leukemia in cats or distemper in dogs don't affect humans. Innate immunity works both ways because some viruses that make humans ill — such as the virus that causes HIV/AIDS — don't make cats or dogs sick.
Innate immunity also includes the external barriers of the body, like the skin and mucous membranes (like those that line the nose, throat, and gastrointestinal tract), which are the first line of defense in preventing diseases from entering the body. If this outer defensive wall is broken (as through a cut), the skin attempts to heal the break quickly and special immune cells on the skin attack invading germs.
Adaptive Immunity
The second kind of protection is adaptive (or active) immunity, which develops throughout our lives. Adaptive immunity involves the lymphocytes and develops as people are exposed to diseases or immunized against diseases through vaccination.
Passive Immunity
Passive immunity is "borrowed" from another source and it lasts for a short time. For example, antibodies in a mother's breast milk provide a baby with temporary immunity to diseases the mother has been exposed to. This can help protect the baby against infection during the early years of childhood.
Everyone's immune system is different. Some people never seem to get infections, whereas others seem to be sick all the time. As people get older, they usually become immune to more germs as the immune system comes into contact with more and more of them. That's why adults and teens tend to get fewer colds than kids — their bodies have learned to recognize and immediately attack many of the viruses that cause colds.
Problems of the Immune System
Disorders of the immune system fall into into four main categories:
immunodeficiency disorders (primary or acquired)
autoimmune disorders (in which the body's own immune system attacks its own tissue as foreign matter)
allergic disorders (in which the immune system overreacts in response to an antigen)
cancers of the immune system
Immunodeficiency Disorders
Immunodeficiencies occur when a part of the immune system is not present or is not working properly. Sometimes a person is born with an immunodeficiency (known as primary immunodeficiencies), although symptoms of the disorder might not appear until later in life. Immunodeficiencies also can be acquired through infection or produced by drugs (these are sometimes called secondary immunodeficiencies).
Immunodeficiencies can affect B lymphocytes, T lymphocytes, or phagocytes. Examples of primary immunodeficiencies that can affect kids and teens are:
IgA deficiency is the most common immunodeficiency disorder. IgA is an immunoglobulin that is found primarily in the saliva and other body fluids that help guard the entrances to the body. IgA deficiency is a disorder in which the body doesn't produce enough of the antibody IgA. People with IgA deficiency tend to have allergies or get more colds and other respiratory infections, but the condition is usually not severe.
Severe combined immunodeficiency (SCID) is also known as the "bubble boy disease" after a Texas boy with SCID who lived in a germ-free plastic bubble. SCID is a serious immune system disorder that occurs because of a lack of both B and T lymphocytes, which makes it almost impossible to fight infections.
DiGeorge syndrome (thymic dysplasia), a birth defect in which kids are born without a thymus gland, is an example of a primary T-lymphocyte disease. The thymus gland is where T lymphocytes normally mature.
Chediak-Higashi syndrome and chronic granulomatous disease both involve the inability of the neutrophils to function normally as phagocytes.
Acquired (or secondary) immunodeficiencies usually develop after someone has a disease, although they can also be the result of malnutrition, burns, or other medical problems. Certain medicines also can cause problems with the functioning of the immune system.
Acquired (secondary) immunodeficiencies include:
HIV (human immunodeficiency virus) infection/AIDS (acquired immunodeficiency syndrome) is a disease that slowly and steadily destroys the immune system. It is caused by HIV, a virus that wipes out certain types of lymphocytes called T-helper cells. Without T-helper cells, the immune system is unable to defend the body against normally harmless organisms, which can cause life-threatening infections in people who have AIDS. Newborns can get HIV infection from their mothers while in the uterus, during the birth process, or during breastfeeding. People can get HIV infection by having unprotected sexual intercourse with an infected person or from sharing contaminated needles for drugs, steroids, or tattoos.
Immunodeficiencies caused by medications. Some medicines suppress the immune system. One of the drawbacks of chemotherapy treatment for cancer, for example, is that it not only attacks cancer cells, but other fast-growing, healthy cells, including those found in the bone marrow and other parts of the immune system. In addition, people with autoimmune disorders or who have had organ transplants may need to take immunosuppressant medications, which also can reduce the immune system's ability to fight infections and can cause secondary immunodeficiency.
Autoimmune Disorders
In autoimmune disorders, the immune system mistakenly attacks the body's healthy organs and tissues as though they were foreign invaders. Autoimmune diseases include:
Lupus, a chronic disease marked by muscle and joint pain and inflammation (the abnormal immune response also may involve attacks on the kidneys and other organs)
Juvenile rheumatoid arthritis, a disease in which the body's immune system acts as though certain body parts (such as the joints of the knee, hand, and foot) are foreign tissue and attacks them
Scleroderma, a chronic autoimmune disease that can lead to inflammation and damage of the skin, joints, and internal organs
Ankylosing spondylitis, a disease that involves inflammation of the spine and joints, causing stiffness and pain
Juvenile dermatomyositis, a disorder marked by inflammation and damage of the skin and muscles
Allergic Disorders
Allergic disorders occur when the immune system overreacts to exposure to antigens in the environment. The substances that provoke such attacks are called allergens. The immune response can cause symptoms such as swelling, watery eyes, and sneezing, and even a life-threatening reaction called anaphylaxis. Medications called antihistamines can relieve most symptoms.
Allergic disorders include:
Asthma, a respiratory disorder that can cause breathing problems, frequently involves an allergic response by the lungs. If the lungs are oversensitive to certain allergens (like pollen, molds, animal dander, or dust mites), it can trigger breathing tubes in the lungs to become narrowed, leading to reduced airflow and making it hard for a person to breathe.
Eczema is an itchy rash also known as atopic dermatitis. Although atopic dermatitis is not necessarily caused by an allergic reaction, it more often occurs in kids and teens who have allergies, hay fever, or asthma or who have a family history of these conditions.
Allergies of several types can occur in kids and teens. Environmental allergies (to dust mites, for example), seasonal allergies (such as hay fever), drug allergies (reactions to specific medications or drugs), food allergies (such as to nuts), and allergies to toxins (bee stings, for example) are the common conditions people usually refer to as allergies.
Cancers of the Immune System
Cancer occurs when cells grow out of control. This also can happen with the cells of the immune system. Lymphoma involves the lymphoid tissues and is one of the more common childhood cancers. Leukemia, which involves abnormal overgrowth of leukocytes, is the most common childhood cancer. With current medications most cases of both types of cancer in kids and teens are curable.
Although immune system disorders usually can't be prevented, you can help your child's immune system stay stronger and fight illnesses by staying informed about your child's condition and working closely with your doctor.
