In which part of the alimentary canal does most digestion occur?

A. stomach

B. proximal small intestine

C. distal small intestine

D. ascending colon

Answer Explanation:

b) proximal small intestine

- Correct: Most digestion occurs in the proximal small intestine, specifically in the duodenum. The duodenum receives chyme from the stomach and plays a crucial role in digestion by mixing the chyme with digestive enzymes and bile. Digestive enzymes from the pancreas, including amylase, lipase, and proteases, break down carbohydrates, fats, and proteins, respectively, in the duodenum. Bile, produced by the liver and stored in the gallbladder, emulsifies fats to aid in their digestion and absorption.

a) stomach

- Incorrect: While digestion begins in the stomach, where proteins are broken down by pepsin and fats are emulsified to some extent by gastric lipase, the majority of digestion occurs in the small intestine, particularly in the duodenum.

c) distal small intestine

- Incorrect: The distal small intestine, including the jejunum and ileum, is primarily involved in nutrient absorption rather than digestion. Although some digestion continues in these regions, the majority of digestive processes have already occurred in the proximal small intestine.

d) ascending colon

- Incorrect: The ascending colon is part of the large intestine and is not directly involved in digestion. Its main function is to absorb water and electrolytes from the indigestible residue of food (feces) before it is excreted from the body.

Therefore, the Correct Answer is B.

Q #1: Pancreatic juice ________.

A. deactivates bile.

B. is secreted by pancreatic islet cells.

C. buffers chyme.

D. is released into the cystic duct.

Answer Explanation

c) buffers chyme.

- Correct: Pancreatic juice contains bicarbonate ions, which act as buffers to neutralize the acidic chyme entering the duodenum from the stomach. This neutralization is essential for maintaining the optimal pH for the activity of digestive enzymes in the small intestine.

a) deactivates bile.

- Incorrect: Pancreatic juice does not deactivate bile. Bile is not deactivated in the digestive process; instead, it aids in the emulsification and digestion of fats in the small intestine.

b) is secreted by pancreatic islet cells.

- Incorrect: Pancreatic juice is secreted by exocrine cells called pancreatic acinar cells, not by pancreatic islet cells. Pancreatic islet cells secrete hormones such as insulin and glucagon, which regulate blood glucose levels.

d) is released into the cystic duct.

- Incorrect: Pancreatic juice is released into the duodenum through the pancreatic duct, not the cystic duct. The cystic duct connects the gallbladder to the common bile duct, allowing bile to be released into the duodenum when needed for digestion.
Q #2: In which organ of the human body is urea produced as a result of the breakdown of amino acids?

A. liver

B. pancreas

C. stomach

D. small intestine

Answer Explanation

A) liver

- Correct: Urea is produced in the liver as a result of the breakdown of amino acids. Amino acids are the building blocks of proteins, and when proteins are metabolized for energy or other purposes, their constituent amino acids are broken down in a process called deamination. During deamination, the amino groups (-NH2) are removed from the amino acids, forming ammonia (NH3). The liver converts ammonia into urea through a series of biochemical reactions known as the urea cycle. Urea is then excreted by the kidneys in the urine, helping to remove nitrogenous waste from the body.

B) pancreas

- Incorrect: The pancreas is an organ involved in the production of digestive enzymes and hormones such as insulin and glucagon. It is not primarily responsible for the production of urea from the breakdown of amino acids.

C) stomach

- Incorrect: The stomach is primarily involved in the mechanical and chemical digestion of food, particularly proteins. While protein digestion begins in the stomach with the action of gastric juices containing enzymes such as pepsin, urea production from the breakdown of amino acids occurs mainly in the liver.

D) small intestine

- Incorrect: The small intestine is primarily involved in the absorption of nutrients from digested food, rather than the production of urea from the breakdown of amino acids. While some amino acids may be absorbed in the small intestine, urea production primarily occurs in the liver.
Q #3: Which of these is most associated with villi?

A. haustra

B. lacteals

C. bacterial flora

D. intestinal glands

Answer Explanation

b) lacteals

- Correct: Villi are small, finger-like projections that extend into the lumen of the small intestine, increasing its surface area for absorption. Lacteals are specialized lymphatic vessels located within the villi. They play a crucial role in the absorption of dietary fats and fat-soluble vitamins. Lacteals absorb digested fats and fat-soluble nutrients and transport them through the lymphatic system to the bloodstream.

a) haustra

- Incorrect: Haustra are pouches or sacculations formed by the longitudinal muscle of the colon. They are characteristic features of the large intestine, particularly the colon, and are not directly associated with villi.

c) bacterial flora

- Incorrect: Bacterial flora (microbiota) refers to the diverse population of microorganisms inhabiting the gastrointestinal tract. While they play important roles in digestion, nutrient absorption, and immune function, they are not specifically associated with villi. They primarily inhabit the large intestine, where they aid in the fermentation of undigested carbohydrates and the production of certain vitamins.

d) intestinal glands

- Incorrect: Intestinal glands, also known as crypts of Lieberkühn or intestinal crypts, are invaginations of the epithelium located between the villi in the mucosa of the small intestine. They contain stem cells that continuously divide to replace the epithelial cells lining the intestine. While they are anatomically close to villi, they are distinct structures responsible for epithelial cell renewal and secretion of intestinal juices, but they are not directly associated with villi.

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In which part of the alimentary canal does most digestion occur?

More Questions on TEAS 7 Science

Q #1: Pancreatic juice ________.

Answer Explanation

Q #2: In which organ of the human body is urea produced as a result of the breakdown of amino acids?

Answer Explanation

Q #3: Which of these is most associated with villi?

Answer Explanation

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