Question 1

Amino acids and glucose are both absorbed by secondary active transport by the small intestinal epithelial cells.

Accepted Answer

Amino acids and glucose are both absorbed by secondary active transport by the small intestinal epithelial cells with the help of carrier proteins that use the electrochemical gradient of sodium ions. This means that the movement of these nutrients across the cell membrane requires energy from the sodium gradient, which is established by the sodium-potassium pump.

Question 2

Considerable vitamin absorption occurs passively in the stomach.

Accepted Answer

Vitamin absorption occurs mainly in the small intestine, not in the stomach. The stomach mainly acts as a holding chamber for food and begins the process of breaking it down with acid and enzymes.

Question 3

The main function of the ileocecal valve/sphincter is to prevent small intestinal contents from entering the large intestine before digestion of food is completed.

Accepted Answer

The ileocecal valve primarily prevents backflow from the large intestine into the small intestine, not to delay entry of contents into the large intestine.

Question 4

Haustral contractions propel the feces one-third to three-quarters the length of the colon in a few seconds.

Accepted Answer

Haustral contractions are slow, segmenting movements in the colon that help mix and slowly move fecal matter, not rapidly propel it over long distances.

Question 5

Lipase breaks down proteins via hydrolysis.

Accepted Answer

Lipase is an enzyme that breaks down lipids, not proteins. Proteins are broken down by proteases via hydrolysis.

Question 6

The primary factor responsible for forward propulsion of chyme through the small intestine is mass movements.

Accepted Answer

Mass movements are large, infrequent contractions that occur in the large intestine, not the small intestine. The primary factor for chyme propulsion in the small intestine is peristalsis.

Question 7

Migration of a new intestinal epithelial cell from the crypt at the base of the villus to the tip of the villus requires about three weeks.

Accepted Answer

The migration of a new intestinal epithelial cell from the crypt to the tip of the villus typically takes about 3 to 5 days, not three weeks.

Question 8

Chylomicrons are aggregates of bile salts, monoglycerides, and free fatty acids.

Accepted Answer

Chylomicrons are not aggregates of bile salts, monoglycerides, and free fatty acids. They are lipoprotein particles that transport dietary lipids from the intestines to other tissues in the body.

Question 9

Protein digestion begins in the stomach under the influence of pepsin; it continues in the duodenal lumen under the influence of pancreatic proteolytic enzymes; and it is completed intracellularly in the small intestinal brush border.

Accepted Answer

Protein digestion does indeed begin in the stomach with the help of pepsin, continues in the small intestine with pancreatic proteolytic enzymes and eventually completed in the small intestinal brush border.

Question 10

Humans are not capable of digesting cellulose, but some of the enteric bacteria have this capability.

Accepted Answer

This statement is true. Humans lack the enzyme needed to break down cellulose, but certain bacteria in our gut have the ability to digest it. This is why cellulose is considered a type of dietary fiber, as it passes through the digestive system largely undigested, providing bulk to stool and promoting regular bowel movements.

Question 11

Most of the fluid presented to the small intestine for absorption has been ingested in the most recent meal.

Accepted Answer

Most of the fluid presented to the small intestine comes from digestive secretions, such as saliva, gastric juice, bile, pancreatic juice, and intestinal secretions, rather than from the fluid ingested in a meal.

Question 12

Excessive small intestinal motility can lead to constipation because there is less time for absorption to take place.

Accepted Answer

Excessive small intestinal motility would lead to the opposite effect of constipation, which is diarrhea. This is because the food moves too quickly through the intestines, leading to a decreased amount of time for absorption to occur.

Question 13

Microvilli establish a brush border in the small intestine.

Accepted Answer

Microvilli are small, finger-like projections on the surface of the small intestine that help to increase the surface area for nutrient absorption. The microvilli establish a brush border, which gives the surface a feathery appearance and helps to trap and absorb nutrients.

Question 14

Colonic secretion contains no digestive enzymes.

Accepted Answer

Colonic secretion mainly contains water, electrolytes, and mucus, and does not contain digestive enzymes.

Question 15

The ileocecal juncture serves as a barrier to prevent bacteria-laden contents of the large intestine from contaminating the small intestine.

Accepted Answer

The ileocecal valve, which is located at the ileocecal junction, acts as a physical barrier to prevent the backflow of fecal matter and bacteria from the large intestine into the small intestine. Therefore, the statement is true.

Question 16

Sodium can be absorbed both actively and passively.

Accepted Answer

Sodium can be absorbed actively through sodium-potassium pumps and passively through ion channels.

Question 17

The main motility seen in the small intestine during digestion of a meal is the migrating motility complex.

Accepted Answer

The main motility in the small intestine during digestion is peristalsis and segmentation, not the migrating motility complex, which occurs between meals.

Question 18

The small intestinal epithelium actively secretes digestive enzymes into the intestinal lumen.

Accepted Answer

The small intestinal epithelium does not actively secrete digestive enzymes into the intestinal lumen. Instead, digestive enzymes are produced by the pancreas and secreted into the duodenum, where they mix with food and aid in digestion.

Question 19

Digestive enzymes produced by the small intestine are not secreted into the lumen.

Accepted Answer

Digestive enzymes produced by the small intestine are secreted into the lumen by the pancreas and liver.

Question 20

Fat is absorbed into the lymph in the form of micelles.

Accepted Answer

Fat is absorbed into the lymph in the form of chylomicrons, not micelles. Micelles are involved in the initial absorption of fatty acids and monoglycerides into the intestinal cells.

Quiz 16: The Digestive System