Kids Research Express

Infection of or damage to any part of the digestive system may affect digestion as well as other bodily functions. Common infectious agents that attack digestive organs include the mumps virus, which often infects the salivary glands; the bacterium Helicobacter pylori, which causes most stomach and duodenal ulcers ; and viruses and bacteria that cause various forms of gastroenteritis, often called stomach flu or traveler’s diarrhea. Appendicitis is an inflammation of the appendix , a tube-like pouch about 9 cm (3.5 in) long that branches off the large intestine. It occurs most commonly among children and young adults. Diarrhea —frequent elimination of loose, watery feces—is a symptom of many disorders that occurs when the large intestine is irritated or inflamed. As a result, food residues move through it too quickly for it to absorb the excess water. The opposite condition, constipation, occurs when the large intestine absorbs too much water because food residues are moving slowly.

Occasionally—in 2 percent of full term and 10 percent of premature male babies—one or, more rarely, both testes will fail to descend from the abdomen into the scrotum during embryonic development. Often the affected testis will descend on its own within a few months of birth. Undescended testis is sometimes caused by dysfunctional hormones that control the development of the spermatic cord, which is comprised of the vas deferens and supporting nerves and blood vessels. When the hormones do not send the correct signals, the spermatic cord does not lengthen sufficiently for the testis to descend, develop normally, and eventually produce sperm. If neither testis descends, the man will be infertile. The problem may be corrected by surgery within the first few years of life. A direct blow to the scrotum or twisting of the testis and spermatic cord may cause painful swelling. If pain is accompanied by fever, the swelling may be caused by infection of the testis or epididymis. Swelling withou

Damage to the hypothalamus can result from surgery, trauma (such as accident or stroke), degeneration due to old age or disease, or a tumor. The results of damage can be varied and depend on the areas of the hypothalamus involved. Diabetes insipidus can be caused by hypothalamic damage, or by damage to the hypothalamic-pituitary tract. This disease reduces vasopressin production, resulting in large volumes of urine being produced at all times. Other hypothalamic disorders can include sexual abnormalities (such as premature puberty ), psychic disturbances, obesity , anorexia, temperature regulation disorders, sleep disorders, and disruption of normal circadian rhythms.

Abdominal pain is a key symptom of both minor ailments and serious diseases . Indigestion is the most common cause of abdominal pain in both adults and children. Additional common causes include inflammation of the lining of the stomach and intestinal tract, constipation, and menstrual cramps. Serious causes of abdominal pain include appendicitis; gallbladder or kidney stones; ulcers of the stomach and small intestine; diverticulitis (inflammation of pouchlike tissue in the large intestine); hepatitis ; inflammation of a kidney , a fallopian tube, the bladder, or the pancreas; an ectopic (tubal) pregnancy; an ovarian cyst; an aortic aneurysm (abnormal widening of the aorta caused by weakness in the vessel wall); and cancer . With these conditions, pain often comes in waves, accompanied by vomiting, sweating, and tenderness of the abdomen when touched.

Diseases of the bone marrow can be life threatening because they disrupt blood cell production, which is essential for survival. Inadequate production of blood cells results in aplastic anemia . The causes of this relatively rare disease are often unknown, although some cases result from exposure to toxic chemicals, such as lead, benzene, or arsenic. Radiation from nuclear explosions or X rays can also damage the marrow because the radioactive elements involved have a strong affinity for bone marrow. Leukemias are cancers that affect bone marrow (as well as other tissues). A cell can become cancerous at any state during the series of divisions that produce red or white blood cells. If a progenitor cell becomes cancerous at the beginning of a series of cell divisions, the leukemia is termed acute. Chronic leukemia results when cells in later stages of division become cancerous.

Fungus Infections, diseases caused by the growth of fungi in or on the body. In most healthy people fungal infections are mild, involving only the skin, hair, nails, or other superficial sites, and they clear up spontaneously. They include the familiar ringworm and athlete's foot . In someone with an impaired immune system, however, such infections, called dermatophytoses, can persist for long periods. The organisms causing dermatophytoses belong to the genera Microsporum , Epidermophyton , and Trichophyton . Fungi can also invade internal organs of the body, especially the lungs , where the infections resemble pneumonia or pulmonary tuberculosis. These infections usually occur in people whose immune system has been suppressed by diseases such as acquired immunodeficiency syndrome (AIDS), by anticancer drugs, or by radiation ; patients being treated with steroid hormones (see Hydrocortisone ); people with diabetes; and those being treated with antibiotic drugs for a long time. Tw

Fainting, sudden dizziness or weakness accompanied by brief loss of consciousness, associated with insufficient oxygen in the brain. The cause is usually a disturbance in blood circulation due to fatigue, pain, shock, abnormal blood pressure, arterial blockage, or heart failure. The person fainting should be placed in a position that will quickly bring blood to the brain, and other aid to blood circulation should be instituted. The cause of fainting should be quickly determined so that further appropriate action can be taken. See First Aid .