36
Explain how villi and microvilli aid in absorption.
  1. Villi and microvilli increase the surface area of the small intestines, which aids in the absorption of bile salts and vitamin B12.
  2. Villi and microvilli increase the surface area of the small intestine, which increases the absorption of nutrients by diffusion.
  3. Villi and microvilli form the inner layer of epithelial tissue in the small intestine and increase the absorption of nutrients from chyme.
  4. Villi and microvilli absorb food through the small intestine via smooth muscle contractions called peristalsis.
37
Ruminants, such as this goat, are able to digest large amounts of plant material. How is plant material passed through, digested, and absorbed in the ruminant digestive system?

Simple outline cross-section of goat showing digestive system.

  1. Food is chewed in the mouth, then passes through the esophagus into the rumen and then the reticulum, which contain microbes that break down cellulose and ferment the ingested plant material. The ruminant regurgitates cud from the rumen, and the food is passed into the omasum for water removal and then into the small and large intestines for nutrient and further water absorption. Waste is excreted through the anus.
  2. Food is chewed in the mouth, then passes through the esophagus into the rumen and then the reticulum, which contain microbes that break down cellulose and ferment the ingested plant material. The ruminant regurgitates cud from the rumen, and the food is passed into the abomasum for water removal and then into the small and large intestines for nutrient and further water absorption. Waste is excreted through the anus.
  3. Food is chewed in the mouth, then passes through the esophagus into the rumen and then the reticulum, which contain microbes that break down proteins and ferment the ingested plant material. Ruminants regurgitate cud from the rumen, and the food is passed into the omasum for water removal and then into the small and large intestines for nutrient and further water absorption. Waste is excreted through the anus.
  4. Food is chewed in the mouth then passes through the esophagus into the reticulum and then the rumen, which contain microbes that break down cellulose and ferment the ingested plant material. The ruminant regurgitates cud from the rumen, and the food is passed into the omasum for water removal and then into the small and large intestines for nutrient and further water absorption. Waste is excreted through the anus.
38
a. How does a stomach ulcer form? 
b. How could you prevent a stomach ulcer from forming in your stomach?
  1. a. When the serosa layer of stomach ruptures and does not reform, an open wound is formed. It may be caused by bacteria
    b. Ulcers can be prevented by eliminating ingesting items that cause degradation of the mucus lining like foods that irritate the stomach.
  2. a. When the mucus lining of the stomach ruptures and does not reform, an open wound is formed. It may be caused by a virus.
    b. Ulcers can be prevented by eliminating ingesting items that cause degradation of the mucus lining, like foods that irritate the stomach.
  3. a. When the mucus lining of the stomach ruptures and does not reform, an open wound is formed. It may be caused by bacteria.
    b. Ulcers can be prevented by ingesting items that will increase the acid content of the stomach.
  4. a. When the mucus lining of the stomach ruptures and does not reform, an open wound forms. It may be caused by bacteria.
    b. Ulcers can be prevented by eliminating ingesting items that cause degradation of the mucus lining, such as foods that irritate the stomach.
39
How is the gallbladder involved in digestion, even though it is considered an accessory organ?
  1. The gallbladder secretes bile to the duodenum, which uses it to break down proteins. It is considered an accessory organ because food does not directly pass through it.
  2. The gallbladder secretes bile to the duodenum, which uses it to break down fats. It is considered an accessory organ because food does not directly pass through it.
  3. The gallbladder secretes bile to the ileum, which uses it to break down fats. It is considered an accessory organ because food does not directly pass through it.
  4. The gallbladder secretes bile to the ileum, which uses it to break down proteins. It is considered an accessory organ because only a very small amount of digestion takes place in the gallbladder.
40
What is the role of saliva in the digestive system?
  1. Saliva contains an enzyme called amylase, which starts the chemical digestion in the mouth by breaking down proteins.
  2. Saliva contains an enzyme called lipase, which starts chemical digestion in the mouth by breaking down proteins.
  3. Saliva contains an enzyme called maltase, which starts chemical digestion in the mouth by breaking down carbohydrates.
  4. Saliva contains an enzyme called amylase, which starts chemical digestion in the mouth by breaking down carbohydrates.
41
What are the biological benefits of a balanced diet?
  1. A balanced diet provides excess energy to be stored in the body and nutrients to maintain good health and increase reproductive capability.
  2. A balanced diet allows excess energy to be stored in the body, thereby increasing the rate of metabolic reactions.
  3. A balanced diet provides nutrients needed to maintain proper bodily functions, and vitamins and minerals to maintain good health and reproductive capability.
  4. A balanced diet provides nutrients needed to maintain proper bodily functions, and vitamins and minerals to maintain good health and increase reproductive capability.
42
Why is it important to eat carbohydrates, which provide organic carbons?
  1. They are needed to provide insulation to mammals.
  2. They help to fight infections.
  3. They are needed to produce antibodies.
  4. They are needed to build cells and tissues.
43
a. Why is it necessary to consume essential nutrients?
b. What are two examples of fat-soluble essential vitamins, and what are their functions in the human body?
  1. a. Essential nutrients are not synthesized by the body and are not necessary for proper body function.
    b. Vitamins B and C are two fat-soluble essential vitamins. Vitamin B helps maintain eyesight, and vitamin C is essential for blood clotting.
  2. a. Essential nutrients are not synthesized by the body but are necessary for proper body function.
    b. Vitamins A and K are two fat-soluble essential vitamins. Vitamin A helps maintain connective tissue, and vitamin K is essential for blood clotting.
  3. a. Essential nutrients are synthesized by the body and are necessary for proper body function.
    b. Vitamins D and K are two fat-soluble essential vitamins. Vitamin D helps maintain a stable nervous system, and vitamin K is essential for blood clotting.
  4. a. Essential nutrients are not synthesized by the body but are necessary for proper body function.
    b. Vitamins A and K are two fat-soluble essential vitamins. Vitamin A helps maintain eyesight, and vitamin K is essential for blood clotting.
44
What happens to glycogen when blood sugar drops?
  1. It stimulates the release of insulin, which can regulate the blood sugar level.
  2. It is released from the liver and converted to glucose to increase blood sugar levels.
  3. It is converted to starch, which breaks down to form glucose and increase blood sugar levels.
  4. It is released from the liver and converted to pyruvate, which can then form glucose to increase blood sugar levels.
45
What is the evolutionary significance of glycogen production?
  1. Excess ATP and glucose produce glycogen, which can be used at a later point in time to act as co-factor if, for example, a good source is scarce.
  2. Excess proteins and glucose produce glycogen, which can be used at a later point in time to produce energy if, for example, food is scarce.
  3. Excess ATP and glucose produce glycogen, which can be used at a later point in time to produce energy if, for example, food is scarce.
  4. Excess proteins and fats produce glycogen, which can be used at a later point in time to act as source of nitrogen if, for example, a good source is scarce.
46
How can eating too much bread and pasta physiologically promote obesity?
  1. Excess blood glucose increases the amount of urea, which is converted into fatty acids. Fatty acids are stored in areolar cells, which increase the amount of body fat.
  2. Excess blood glucose increases the amount of pyruvate, which is converted into fatty acids. Fatty acids are stored in adipose cells, which increase the amount of body fat.
  3. Bread and pasta are rich in fats. Their digestion produces fatty acids and glycerol. Fatty acids are stored in adipose cells, which increase the amount of body fat.
  4. Bread and pasta are rich in fats. Their digestion produces fatty acids and glycerol. Fatty acids are stored in areolar cells, which increase the amount of body fat.
47
How do ingestion and digestion differ?
  1. Ingestion is taking food in through mouth, where mechanical digestion begins. Chemical digestion begins in the stomach, where food is further broken down into smaller molecules that can be absorbed and used by the body.
  2. Ingestion is the process of taking in food through the mouth, where mechanical and chemical digestion begins to break down the food into smaller molecules that can be absorbed and used by the body.
  3. Ingestion is taking food in through the mouth, where mechanical and chemical digestion begins. Digestion in the stomach breaks down proteins and fats present in food into smaller molecules that can be absorbed and used by the body.
  4. Ingestion is the transfer of food from the mouth to the esophagus, where mechanical and chemical digestion begin to break down the food into smaller molecules that can be absorbed and used by the body.
48
Why are some dietary lipids a necessary part of a balanced diet?
  1. Dietary lipids aid in the absorption of water-soluble vitamins, including B and C, which are needed for various bodily functions.
  2. Dietary lipids aid in the absorption of some minerals, including folic acid, iron, and magnesium, which are needed for various bodily functions.
  3. Dietary lipids aid in the absorption of vitamins, including A, B, C, D, E, and K, which are needed for various bodily functions
  4. Dietary lipids aid in the absorption of fat-soluble vitamins, including A, D, E, and K, which are needed for various bodily functions.
49
What happens to undigested food after the water is reabsorbed?
  1. Undigested food is moved through the colon, where intestinal flora aid in digestion by peristalsis, and then stored in the rectum until elimination through the anus.
  2. Undigested food is moved through the colon, where intestinal flora aid in digestion by peristalsis; further absorption takes place in the rectum, after which it stores the food until elimination through the anus.
  3. Undigested food is moved through the colon, where intestinal flora aid in digestion by segmentation, and then it is stored in the rectum until elimination through the anus.
  4. Undigested food is moved through the ileum, where intestinal flora aid in digestion by peristalsis, and then it is stored in the rectum until elimination through the anus.
50
a. What are micelles?
b. Why are micelles integral to lipid absorption?
  1. a. Micelles are lipoproteins designed for the transport of lipids that enter lacteals. 
    b. Micelles facilitate absorption by microvilli, where the fatty acids and proteins diffuse out to form lipoproteins.
  2. a. Micelles are lipoproteins designed for the transport of lipids that enter lacteals. 
    b. Micelles facilitate absorption by microvilli, where the fatty acids and monoglycerides diffuse out to form triglycerides.
  3. a. Micelles are bile salt–surrounded fatty acids and phospholipids.
    b. Micelles facilitate absorption by microvilli, where the fatty acids and monoglycerides diffuse out to form triglycerides.
  4. a. Micelles are bile salt–surrounded fatty acids and monoglycerides.
    b. Micelles facilitate absorption by microvilli, where the fatty acids and monoglycerides diffuse out to form triglycerides.
51
On a cellular level, why must food be broken down?
  1. Large molecules present in intact food pass through the digestive epithelium and enter the cell through the membrane, thereby damaging the nuclear membrane. Hence it must be broken down.
  2. Fats present in intact food contain very large molecules, which cannot pass through cell membranes. Fats need to be passed through the digestive epithelium to be utilized.
  3. Large molecules present in intact food cannot pass through cell membranes. Nutrients need to be passed through the digestive epithelium to be utilized.
  4. Large molecules, if not broken down, produce toxic substances that pass through the epithelium of the digestive tract and are utilized by the cells. This can be lethal to the cell.
52
What is the importance of neural responses to food stimuli?
  1. Neural responses facilitate secretion of fumarase needed for chemical digestion of food as well as other involuntary responses like peristalsis.
  2. Neural responses facilitate secretion of enzymes that are needed to digest or break down food as well as other involuntary responses like segmentation in stomach.
  3. Neural responses facilitate secretion of enzymes needed to digest or break down food as well as other involuntary responses like peristalsis.
  4. Neural responses facilitate secretion of salivary amylase needed to digest or break down food as well as secretion of hormones like secretin and gastrin.
53
How do hormones regulate digestion?
  1. Hormones regulate aspects of digestion such as increasing the peristaltic movements in the esophagus when food is sensed.
  2. Hormones regulate digestion by signaling when the stomach is full or empty so that an individual will consume food or stop eating.
  3. Hormones like gastrin, secretin, adrenocorticotropic are released from the pituitary to regulate which digestive secretions are released.
  4. Hormones regulate aspects of digestion such as which digestive secretions are released as well as when they are released.
54
When you are eating a meal, how do you know when you are full?
  1. The pituitary gland release hormones when the stomach is full, which therefore reduces hunger.
  2. The brain signals when the stomach is full that you are satiated, which therefore reduces hunger.
  3. The stomach signals when it is full, which therefore reduces hunger.
  4. Low blood sugar levels stimulate a neurotransmitter, which sends a signal to the brain when the stomach is full and therefore reduces hunger.