chapter 14 Flashcards

Question

What is the function of the gallbladder?

Answer 1

The bile produced by the liver flows through ducts to the gallbladder. The gallbladder concentrates bile by removing most of the water and then stores the concentrated bile until it is needed. After a meal, bile is secreted into the small intestine via the common bile duct, which joins the pancreatic duct.

Answer 2

By the time the contents of the digestive tract reach the large intestine, most of the nutrients and water have been absorbed. The large intestine absorbs most of the remaining nutrients and water and stores the now nearly solid waste material until it can be eliminated.

Answer 3

A small fingerlike pouch, the appendix, extends from the cecum. The appendix has no known digestive function, but we become acutely aware of its presence if it becomes inflamed or infected, a condition called appendicitis

Answer 4

Nutrients need to be broken down to their smallest forms (monomers) in order to be absorbed into the body from inside the lumen of the GI tract. Proteins are broken down by proteases (pepsin, trypsin...) into Amino Acids then absorbed. Carbohydrates are broken down by amylase into monosaccharides (like glucose) then absorbed. Lipids (like triglycerides) are broken down by lipase (with the help of bile) into free fatty acids and then absorbed. Be able to state which class of nutrients are digested by which class of enzymes to form which absorbable monomers. (Know what is listed above.)

Answer 5

Carbohydrates are one of the body’s main sources of energy, and many nutritionists recommend that approximately 45–65% of our calorie intake come from carbohydrates. Carbohydrates may be either simple or complex.

Answer 6

Lipids (including fats) are essential components of every living cell. Phospholipids and cholesterol make up most of the cell membrane. Cholesterol also forms the backbone of steroid hormones and is used to synthesize bile. Fat stores energy and several vitamins, cushions organs, and insulates the body under the skin. Most of the fats in food are triglycerides, which consist of three fatty acids attached to a glycerol molecule. Recall (from Chapter 2) that fats are classified as either saturated or unsaturated, according to the ratio of hydrogen to carbon atoms in their fatty acids (Figure 14.17). ● Saturated fats have two hydrogen atoms for every carbon atom in their fatty acid tails. They tend to be solids at room temperature. Red meats and dairy products are higher in saturated fats than poultry and fish. Saturated fats are also found in a few plant sources such as coconut and palm kernel oil. They tend to raise blood levels of LDL cholesterol, the “bad” cholesterol that is associated with atherosclerosis and heart disease (Chapter 8). ● Unsaturated fats are missing one or more pairs of hydrogen atoms in their fatty acid tails. Every missing pair of hydrogen atoms leads to a double bond between adjacent carbons and a kink, or bend, in the tail, making it more difficult for adjacent molecules to form bonds with each other. Consequently, unsaturated fats are liquids (oils) at room temperature. In general, unsaturated fats are considered healthier than saturated fats because they tend to lower LDL cholesterol levels. Olive, canola, safflower, and corn oils are all unsaturated fats derived from plants. Certain cold-water fish (salmon, trout, and sardines) are rich in omega-3 fatty acids, polyunsaturated fatty acids that have been linked to a reduced risk of heart disease.

Answer 7

Despite their variety, all proteins are composed of just 20 different amino acids. The body can make 12 of these amino acids.

Answer 8

The 8 that the body cannot produce (isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine) are called essential amino acids because they must be ingested in food. Two more that the body can make, histidine and arginine, are sometimes considered essential in children because their rapidly growing bodies cannot synthesize these amino acids fast enough.

Answer 9

A complete protein contains all 20 of the amino acids in proportions that meet our nutritional needs. Most animal proteins are complete, but nearly all plant proteins (with the exception of soybeans) lack one or more of the essential amino acids. Vegetarians must be careful to choose the right combinations of plant-based foods to obtain all amino acids. A combination of foods from any two of the three rightmost columns of Figure 14.18 will provide the necessary balance of all essential amino acids. Foods such as trail mix (roasted soybeans and nuts), hummus (chick peas and sesame seeds), a bean burrito in a corn tortilla, and red beans and rice do just that.

Answer 10

In addition to carbohydrates, lipids, and proteins, humans need vitamins, a group of at least 13 chemicals that are essential for normal functioning. The body can produce only a few vitamins; our skin synthesizes vitamin D when exposed to sunlight, and bacteria living in the colon manufacture vitamins K, B6, and biotin. We must obtain all others from our food and absorb them in the digestive tract. Table 14.2 lists the 13 vitamins along with their sources, functions, and signs of deficiency or excess. Vitamins fall into two groups: fat soluble and water soluble. The distinction reflects how a vitamin is absorbed and stored and how steady a supply of it is needed. Fat-soluble vitamins are absorbed more readily if there is fat in the diet. They tend to be absorbed along with the components of fat, and they are stored in fat tissue and released as needed. Body stores of some fat-soluble vitamins may last for years, so it is rarely necessary to take supplements. Water-soluble vitamins are absorbed more readily than fat-soluble vitamins, but they are stored only briefly and rapidly excreted in urine. Thus we need to consume foods containing water-soluble vitamins on a regular basis. Minerals are the atoms of certain chemical elements that are also essential for body processes. They are the ions in blood plasma and cell cytoplasm (sodium, potassium, chloride, and many others). They represent most of the chemical structure of bone (calcium, phosphorus, and oxygen). They also contribute to the activity of nerves and muscles (sodium, potassium, and calcium), among many other functions. Twenty-one minerals are considered essential for animals. Nine of the 21 (arsenic, chromium, cobalt, manganese, molybdenum, nickel, selenium, silicon, and vanadium) are called trace minerals because they represent less than 0.01% of your body weight. Table 14.3 lists the 12 most important minerals. How much do we need of each vitamin and mineral? The National Research Council publishes the current best estimate, the Recommended Dietary Allowance (RDA). Most healthy people can achieve the RDA without taking supplements if they eat a balanced diet of whole foods. That’s a big “if” for some of us, considering our diets. Scientific studies suggest that supplements may also benefit certain groups, such as newborns, the elderly, or people taking medications that interfere with nutrient absorption. Calcium is advised for postmenopausal women to prevent the bone loss of osteoporosis. Never take massive doses of any vitamin or mineral unless prescribed by your doctor. As the “excess” columns show, more is not always better.

Answer 11

Fiber—found in many vegetables, fruit, and grains—is indigestible material. Even though our bodies cannot digest it, we need a certain amount in our diet. Fiber is beneficial because it makes feces bulky and helps them pass more efficiently through the colon. A low-fiber diet can lead to chronic constipation, hemorrhoids (swollen veins in the lining of the anus, often caused by straining during defecation), and a disorder called diverticulosis (see section 14.12). A low-fiber diet has also been associated with a higher risk of colon cancer, perhaps because cancer-causing substances remain in the colon longer (see Chapter 18). Doctors recommend eating 20–35 grams of fiber every day—considerably more than the average 12–17 grams that most North Americans consume.

Answer 12

Food labels

Answer 13

The body requires energy to fuel essential activities such as breathing and maintaining organ function, as well as for physical activity. Energy is measured in units called calories. Technically, a calorie is the amount of energy needed to raise the temperature of 1 gram of water by 1° C. Because this is not much energy in biological terms, nutritionists generally measure the energy content of food and the energy used to perform biological activities in terms of kilocalories (1,000 calories). However, in subsequent usage the “kilo” is usually dropped, and consequently a kilocalorie of energy is referred to as just one nutritional calorie. We will follow that convention here as well.

Answer 14

Your daily caloric energy needs are determined primarily by your basal metabolic rate (BMR), the energy your body requires to perform all essential activities except physical activity. BMR is influenced by the following factors: ● Gender and body composition. BMR is higher in males and higher in muscular men and women. ● Age. BMR declines over time. ● Health. Some health conditions (such as fever, infections, and hyperthyroidism) increase BMR. Other conditions (such as hypothyroidism) lower it. ● Food intake. Eating increases BMR, whereas fasting and extreme dieting decrease it. This is why crash diets often fail to lower body weight permanently. Although weight may fall temporarily, a lower BMR makes it difficult to keep the pounds from returning. ● Genetics. Genetics plays a role in determining your BMR, although precisely how has not been determined. By definition, BMR only includes a person’s basal metabolic energy needs. Most people’s energy expenditure is 50–100% higher than their BMR unless they spend all day in bed. The additional energy is expended in physical activity.

Answer 15

Numerous studies reveal a direct correlation between obesity and the incidence of heart disease, diabetes, cancer, arthritis, and other health problems. The connection is strong enough that government groups and insurance companies regularly publish charts that use a person’s height and weight to define body mass index (BMI). Read your own BMI from the chart in Figure 14.20

Answer 16

30 or higher

Answer 17

Anorexia nervosa (anorexia) is a condition in which a person diets excessively or stops eating altogether, even to the point of starvation and death. Untreated anorexia has the highest mortality rate of any mental illness. One of the most famous anorexics was singer Karen Carpenter, who died in 1983 at the age of 32. Symptoms include the following: ● Refusal to maintain healthy body weight; people with anorexia often weigh less than 85% of their ideal weight. ● Intense fear of gaining weight, even though underweight. ● Distorted perception or preoccupation with body weight or shape. ● In premenopausal women, the absence of at least three consecutive menstrual cycles. Severe undernutrition interferes with the hormonal cycles of menstruation. Male anorexics also experience hormonal abnormalities.

Answer 18

Bulimia nervosa (bulimia) is a binge-and-purge condition in which someone eats and deliberately vomits or takes other steps to minimize the calories ingested. Symptoms of bulimia include the following: ● Recurrent episodes of binge eating. An episode of binge eating involves both (1) eating large amounts of food and (2) feeling a lack of control over eating. ● Taking recurrent inappropriate steps to prevent weight gain, such as self-induced vomiting; misusing laxatives, diuretics, enemas, or other medications; fasting; or exercising excessively. ● Binge eating and compensatory behaviors that occur, on average, at least twice a week for three months. ● Preoccupation with body shape and weight. However, unlike anorexics, some bulimics maintain a normal weight.

Answer 19

Binge eating disorder is like bulimia but without the purge. Binge eaters simply have no control over how much they eat on certain occasions. They are compulsive eaters, likely to eat even when they are not hungry. All three forms of eating disorders play havoc with the body and mind. Anorexics become malnourished and suffer insomnia, hair loss, fatigue, and moodiness. Over time, they lose bone mass and develop osteoporosis (Figure 14.22). Bulemics are likely to suffer ulcers, chronic heartburn, and rectal bleeding due to repeated trauma to the digestive system. Recurrent vomiting also damages gums, erodes tooth enamel, and makes salivary glands swell, giving the bulimic a chipmunklike appearance. Binge eaters have a tendency to become obese (but that does not mean that all obese persons are binge eaters). The underlying causes of (or triggers for) eating disorders are not well known but seem to vary widely. They may include low self-esteem, fear, or anxiety; a dysfunctional home life; a feeling of helplessness and a desire for control where there is none; difficulty managing emotions and a tendency toward depression; or unhappiness with one’s physical appearance. These are complex emotional issues rather than dietary or nutritional ones. Effective treatment of eating disorders generally requires a team of professionals who can address the patient’s medical, psychiatric, dental, psychological, and nutritional needs.

Answer 20

Human infants are born with the enzyme lactase in their small intestines for digesting lactose, the primary sugar in milk. However, many adults gradually lose the enzyme, and with it their ability to digest lactose. The result is lactose intolerance. Symptoms of lactose intolerance include diarrhea, gas, bloating, and abdominal cramps after ingesting milk products. Diarrhea occurs because the undigested lactose causes fluid to be retained in the digestive tract. The gas, bloating, and abdominal cramps are due to bacterial fermentation of the lactose, which produces gases. Lactose-intolerant people can eat cheese or yogurt because the lactose in these milk products has already been digested. Lactose-free milk is also available.

Answer 21

Peptic ulcers are painful erosions of the mucosal lining of the stomach or duodenum. Most peptic ulcers are associated with infection by one of the few bacteria that can live in the acidic environment of the stomach, called Helicobacter pylori. The bacterial infection leads to chronic inflammation, an increase in gastric acid secretion, and damage to the mucosal lining. Peptic ulcers can also be caused by excessive use of aspirin or nonsteroidal antiinflammatory drugs (NSAIDs). NSAIDs block the production of the mucus that protects the gastric mucosa from gastric acid. After treatment to eliminate any H. pylori infection, most peptic ulcers heal on their own. Antacids may also be prescribed as needed. The use of aspirin and NSAIDs should be discontinued if possible.

Answer 22

When people with celiac disease (also known as sprue) eat gluten, a protein found primarily in wheat, rye, and barley, their immune systems respond by damaging or destroying the villi that line the small intestine. The result is malabsorption of nutrients of all kinds, not just gluten. Celiac disease is an inherited disorder with a prevalence of about 1 in 130 persons. Symptoms vary widely, from acute abdominal pain and vomiting to chronic fatigue, depression, and eventually malnutrition, depending on a person’s age, how much gluten they eat, and how sensitive they are to it. Celiac disease often goes undiagnosed at first because its symptoms are so varied and so similar to other diseases and conditions. A definitive diagnosis is made by a blood test for a certain autoantibody in the patient’s blood. The only effective treatment is a gluten-free diet

Answer 23

Inflammation of the liver, referred to as hepatitis, is generally caused by viruses or toxic substances. Researchers have identified at least five viruses that cause hepatitis. The most common are hepatitis A, B, and C. Hepatitis A is transmitted by contaminated food or water and causes a brief illness from which most people recover completely. A vaccine is available for hepatitis A. Although the vaccine is not considered necessary for most residents of industrialized nations, it may be a good idea for travelers to underdeveloped countries. Hepatitis B travels in blood or body fluids, so it is usually passed via contaminated needles, blood transfusions, or sexual contact with infected individuals. Approximately 300,000 new cases are diagnosed each year. If not treated, hepatitis B can lead to liver failure. Symptoms include jaundice (the skin takes on a yellowish color due to accumulated bile pigments in the blood), nausea, fatigue, abdominal pain, and arthritis. A vaccine is available for hepatitis B. Federal law requires all health care workers to be vaccinated. Hepatitis C is also transmitted in infected blood, usually through contaminated needles or blood transfusions. By 1992, U.S. blood banks began routine testing for hepatitis C, so the risk of contracting it from transfusions has fallen. However, researchers estimate that as many as 4 million Americans may already be infected, and many of them have no symptoms. Hepatitis C may remain dormant for years but still damage the liver. Severe cases can lead to chronic hepatitis, cirrhosis, or liver cancer. Doctors recommend testing for anyone who has had kidney dialysis (Chapter 15) or an organ transplant before 1992. Also at risk are those who have injected drugs or had sexual contact with a hepatitis C carrier.

Answer 24

The gallbladder normally concentrates bile about 10-fold by removing about 90% of the water. Excessive cholesterol in the bile may precipitate out of solution with calcium and bile salts, forming hard crystals called gallstones (Figure 14.23). Only about 20% of gallstones ever cause problems, but if the crystals grow large enough they can obstruct bile flow and cause intense pain, especially after a meal. Treatments include drugs to dissolve the crystals, ultrasound vibrations or laser treatments to break the stones apart, or surgery to remove the gallbladder.

chapter 14 Flashcards

(52 cards)