Object Oriented Programming - Guía Docente 2015/16

that affects the body’s ability to produce the enzyme glucose-6-phosphate dehydrogenase (G6PD). G6PD deficiency is an X-linked chromosomal disorder, making it more common in men; it also is more common among men of Mediterranean and African-American descent. Health experts estimate that more than 10 percent of African-American men in the Unites States have G6PD deficiency. G6PD is necessary for the health and normal function of red blood cells; it helps to neutralize oxidants (by- products of oxidation or oxygen metabolism).

Most of the time, G6PD deficiency causes no problems. When stress, intense physical activity, fever, or certain medications increase oxidation, however, there is not enough G6PD to handle the resulting increase in oxidants and cell damage occurs. The most vulnerable cells in the blood are the red blood cells, which rupture and die. This results in hemolytic anemia—a reduced ability of the blood, due to a shortage of red blood cells, to transport oxygen. The anemia typically resolves as the bone marrow produces new red blood cells and the red blood cell count returns to normal.

G6PD deficiency is sometimes called favism, as the fava bean, also called the broad bean (a dietary sta- ple in many parts of the world), contains substances that increase oxidative reactions. Other such substances include antimalarial medications, ASPIRIN, sulfonamide antibiotics, ascorbic acid (vitamin C), and the ANTI-ARRHYTHMIA MEDICATIONSprocainamide (Pronestyl, Pronestyl SR), and quinidine (Cardio- quin). Other than avoiding substances that increase oxidation, G6PD deficiency requires no treatment.

See also ANTIOXIDANT.

gallbladder disease Inflammation or infection of the gallbladder or blockage of the bile ducts by gall-

stones. Gallbladder disease becomes more common with increasing age. The gallbladder is a small, muscular, pouchlike organ underneath the liver. Its primary function is to store bile, a substance the body needs to digest fats. The liver produces bile and sends it to the gallbladder. During digestion, the small intestine releases the ENZYMEcholecystokinin (CCK), which causes the gallbladder to contract and release bile into the intestine. Gallbladder disease occurs when there is any interruption of or inter- ference with this process. Pain is the primary symp- tom of gallbladder disease that sends people to the doctor and sometimes to the hospital emergency department as it can be intense. Ultrasound exami- nation can diagnose most forms of gallbladder disease though often doctors use magnetic resonance imaging (MRI) or a computed tomography (CT) scan. Other procedures such as cholescintigraphy (HIDA scan) and endoscopic retrograde cholangiopancre- atography (ERCP) can provide additional diagnostic information when necessary. There are two general classifications of gallbladder disease, calculous (with stones) and acalculous (without stones).

Gallstones

Gallstones are irregularly shaped pellets made pri- marily of cholesterol and bile salts; their presence in the gallbladder is called cholelithiasis. Researchers do not know what causes them to develop. Small gallstones commonly form and pass from the gallbladder into the small intestine without incident or awareness of their presence. The majority of gallstones are detected during abdominal X-rays or ultrasound done for other purposes. Gallstones are harmless unless they block one of the bile ducts, in which case they can cause often excruciating pain, inflammation, and infection at the site of the blockage and can cause the pancreas to become inflamed

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(pancreatitis). Pain generally is on the right side of the upper abdomen, though can radiate to the right shoulder and to the left upper abdomen. Gallstones that block the pancreatic duct between the pancreas and the liver, because of the duct’s location on the upper left side of the abdomen, often prove to be the source of pain feared to be heart attack.

Gallstones that cause no symptoms need no treatment. Obstructive gallstones generally need to be surgically removed to relieve pain and prevent infection from developing at the site of the blockage. ERCP sometimes permits the surgeon to snare and remove a gallstone that has become lodged in the common bile duct or the pancreatic bile duct without the need for more extensive surgery. When ultrasound shows multiple gallstones are present, the preferred treatment usually is surgical removal of the gallbladder. Medications to dissolve gallstones are available, though are appropriate and effective only in about a third of men who have gallstones. The most commonly prescribed medication is ursodeoxycholic acid (Actigall); treatment takes one to two years and works only on small gallstones. Extracorporeal shock wave lithotripsy (ESWL), in which high-energy ultrasound waves target the gallstone to break it into smaller fragments, is an option in some cases where there is a single, small stone.

Gallstones are less common in men than in women, though are more likely to develop in men who have DIABETES, have CORONARY ARTERY DIS- EASE(CAD), or who take either of the LIPID-LOWER-

ING MEDICATIONS gemfibrozil (Lopid) or clofibrate

(Atromid-S), as these medications decrease blood cholesterol by increasing the cholesterol content of the bile. Men who are obese or who lose more than 20 percent of their body weight by following a very low-fat, low-calorie diet for longer than three months have increased risk for gallstones as well; as many as a third of men who undergo gastric reduction surgery for weight loss because of extreme OBESITY develop gallstones within a few years of having had the surgery. LIVER DISEASE,

particularly chronic cirrhosis, also increases the risk for gallstones. There also are correlations between cigarette smoking and gallbladder disease, and between gallbladder disease and heart disease.

Acalculous Gallbladder Disease

Sometimes gallbladder disease develops without the presence of gallstones and, when it occurs in men, is most common in middle age. The gallbladder may become inflamed following the passage of a gallstone or for no apparent reason. This condi- tion is called cholecystitis. An inflamed gallbladder generally is enlarged and tender when the doctor examines the upper left abdomen. Bile further aggravates the inflammation and infection can develop. Acalculous gallbladder disease may get better with symptomatic relief (medication to relieve pain) or with ANTIBIOTIC MEDICATIONS, though it tends to recur. When the gallbladder ceases to function, it generally is necessary to take it out, as the risk for infection or the formation of gallstones is high when the bile stagnates in the gallbladder. A HIDA scan (also called a cholescinti- gram) is a radionuclide test that measures the gallbladder’s motility (the amount of bile ejected when the gallbladder contracts); a result, called an ejec- tion fraction, of less than 50 percent indicates a nonfunctioning gallbladder. Other causes of gallbladder disease include cholesterolosis (deposits of cholesterol within the tissues of the walls of the gallbladder), cholesterol polyps (small, stemmed growths inside the gallbladder), and, rarely in the United States, cancer.

Gallbladder Surgery

Surgery to remove the gallbladder can be done laparoscopically in about 80 percent of people with gallbladder disease. Laparoscopic cholecystectomy requires four or five small incisions through which the surgeon inserts the laparoscope and instru- ments. The operation generally requires an overnight stay in the hospital; many people are back to limited regular activities within two weeks and full activities in six weeks. An open cholecystectomy requires a fairly large incision in the upper right abdomen, to expose the liver and allow the surgeon to get to the gallbladder beneath it. Open cholecystectomy may require four or five days in the hospital and a recovery period of four to six weeks before return to limited activities is possible. Full recovery may take 10–12 weeks. Removal of the gallbladder ends all symptoms for 85 percent of those who undergo the surgery. The remaining 15

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percent may have lingering discomfort, particularly after eating a fatty meal. There are no special dietary requirements after gallbladder surgery; the body adapts to the gallbladder’s absence within six to eight weeks after its removal.

Prevention

Many aspects of gallbladder disease are related to lifestyle, particularly dietary habits and WEIGHT

MANAGEMENT. Weight loss, if necessary, should take

place consistently and gradually, at a rate of no more than two pounds a week and 20 percent of body weight over six months. More rapid weight loss, including as a result of bariatric surgery such as gastric banding, greatly increases the risk for gallstones. This is because most rapid weight loss diets are extremely low in fat and calories, which allows the bile to become concentrated in the gallbladder and to begin crystallizing, the first step in the formation of gallstones. Some studies sug- gest that regular moderately intense exercise reduces the risk of gallstones in men.

See also GASTROINTESTINAL SYSTEM; NUTRITION

AND DIET.

garlic An herb used for centuries to treat or prevent various health problems. Though research has yet to scientifically validate many of the benefits attributed to garlic, studies have shown that garlic’s allium compounds are effective in reducing blood cholesterol levels, have a mild anticoagulant effect, and may function as antioxidants that help prevent stomach and colorectal cancers. There is some evi- dence that allium also causes blood vessels to relax (vasodilation), leading to speculation that garlic can help lower BLOOD PRESSURE. For the vast majority of

men, there are no health risks associated with tak- ing medicinal doses of garlic, and many doctors believe the potential health benefits support its use. Many men prefer garlic supplements to natural garlic, as supplements are available in odorless formu- lations. Some men find that natural garlic consumed in the quantities necessary for health benefits (four to eight cloves daily) causes dyspep- sia (stomach irritation), a side effect not as common with supplements.

There is some concern that garlic interferes with the actions of the anti-AIDS medication saquinavir. In a study conducted by researchers at the

National Institutes of Health in 2001, garlic reduced blood levels of saquinavir by half, an effect that extended for several weeks after stopping the garlic. Garlic may also affect the actions of other prescription medications, particularly those taken

for HEART DISEASE.

See also CHOLESTEROL, BLOOD; HIV/AIDS; HERBAL

REMEDIES.

gastroenteritis An infection of the intestines, often called the “stomach flu” (though it is not an influenza), characterized by nausea, vomiting, and diarrhea. Healthy adults generally recover from gastroenteritis without the need for medical treatment in five to seven days. A doctor should evalu- ate gastroenteritis in which:

• It is impossible to keep down any fluids. • Frequent diarrhea or vomiting lasts longer than

three days.

• There is blood or excessive mucus in the stool. • There is intense abdominal pain.

• There is an anal discharge.

The causes of gastroenteritis are multiple and varied, and often remain unknown. Health experts suspect that many cases of gastroenteritis are actu- ally FOOD-BORNE ILLNESSES. Persistent vomiting and diarrhea can cause dehydration and electrolyte imbalance, and may indicate a bacterial or parasitic infection that requires medication. Gastroenteritis with anal discharge is a sign of rectal GONORRHEA. Bloody stools may be the result of irritation from diarrhea or may indicate intestinal bleeding that should be further investigated. Drinking weak tea or flat cola can soothe nausea, as can sucking on a small piece of ginger root or mixing ground ginger with a liquid such as tea. Frequent HANDWASHINGis important to help prevent the spread of illness.

See also ANTACID.

gastrointestinal system The organs and struc- tures that ingest and digest food, and pass digestive waste from the body. The gastrointestinal system supplies the body with the nutrients it needs to fuel its myriad activities, from molecular interac-

tions to integrated networks of function. What enters the body as a meal embarks on a turbulent, convoluted journey through 30 feet of muscular conduits, also called the alimentary canal. The average meal takes 24–30 hours to complete the passage, by the end of which all nutritionally use- ful substances have been extracted to leave residue that bears no resemblance to its original composi- tion. Seven stations along the way blend, churn, and dissolve the meal: mouth, esophagus, stomach, small intestine, large intestine (colon), rectum, and anus. Three additional organs support these stations: the pancreas, the gallbladder, and the liver.

The Journey’s Start: The Mouth and Esophagus Food enters the gastrointestinal system through the mouth. The teeth tear and grind the food into small particles. Three pairs of salivary glands in the mouth produce between a half-ounce and an ounce of saliva for each mouthful of food. Saliva contains a few digestive ENZYMES, though its primary purpose is to form the mouthful of food into a semisolid ball called an alimentary bolus. The tongue pushes the bolus to the back of the throat and into the top of the esophagus, a muscular tube about 10 inches long. A powerful series of wave- like contractions pull it down the esophagus to the stomach. Chewing also releases hormones that promote digestion in the intestines.

Middle Passage: Stomach and Small Intestine In the stomach, the digestive action starts in earnest, bathing the bolus in a powerful acid solu- tion. The stomach is a hollow structure tucked under the bottom of the rib cage, in the upper left abdomen. The stomach’s outer structure is three layers of muscle, with the fibers of each layer run- ning a different direction—one layer across, one layer lengthwise, and one layer wrapped around. Gastric glands, which produce hydrochloric acid and digestive enzymes, line the inner wall of the stomach. Interspersed among them are cells that secrete a thick mucus to protect the stomach from its digestive juices. Empty, the stomach has a volume of about 16 ounces or one pint. It can stretch to hold more than three times that volume, about 56 ounces (31_⁄

wall compresses and churns the food, mixing it with acid and enzymes until, after about six hours, the bolus has become a liquified blend called chyme. A ring of muscle at the bottom of the stomach, the pyloric sphincter, periodically opens to allow small surges of chyme to enter the duodenum, the first segment of the small intestine.

The small intestine is the longest component of the gastrointestinal system; its 18 feet or so of soft, tubelike structure lay in convoluted folds within the central abdomen. There are three seg- ments to the small intestine: the duodenum (about 12 inches long), the jejunum (about 61_⁄

2to seven feet

long), and the ileum (about 10 feet long). For the next 12–20 hours, gentle contractions massage the chyme through the small intestine. Various digestive enzymes enter the mix along the way, separating out nutrients and breaking them into their molecular components. Millions of microscopic tendrils, the intestinal villi, line the walls of the small intestine. The villi extend into the capillary beds, where wait- ing blood picks up the molecules of nutrients that migrate across the membrane coverings of the villi. By the time the chyme reaches the end of the small intestine, little of nutritional value remains.

Adding to the Mix: Pancreas, Liver, and Gallbladder

The liver and pancreas produce numerous digestive enzymes that enter the intestinal tract through channels called ducts. The liver also produces bile and cholesterol, which are necessary to digest and transport lipids and fatty acids. The gallbladder stores bile to make it more rapidly available; in response to a rise in the digestive enzyme chole- cystokinin (CCK), the gallbladder releases bile into the common bile duct, which then drains into the duodenum. Some digestive enzymes the pancreas produces are inactive until they mix with other enzymes in the duodenum.

Journey’s End: Colon, Rectum, and Anus The remnants of digestion pass from the small intestine to the large intestine or colon. The colon’s lining absorbs much of the water still in the sludge- like material and compacts the residue that is left. At the end of the six to eight feet of colon, the digestive waste is in a semisolid form. This material—

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feces—enters the rectum, where it waits to be ex- pelled through the anus as a bowel movement.

Maintaining Gastrointestinal Health A healthy, efficient gastrointestinal system requires a diet with adequate fiber and a balance of nutrients. Fiber gives substance to the chyme, aiding in its movement through the small intestine. Fiber is particularly essential at the end of the digestive journey, helping to retain enough fluid in the feces so they pass easily. Fiber also absorbs cholesterol and fatty acids, reducing the amounts of each that enter the bloodstream. Daily physical exercise such as walking stimulates a meal’s movement through the gastrointestinal system, helping to prevent stag-

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