D313 Anatomy and Physiology II - Set 1 - Part 3

Correct Answer: Brush border enzymes

Option a is correct because brush border enzymes are embedded in the microvilli membranes of the small intestine and perform the final breakdown of proteins and carbohydrates into absorbable monomers. Option b is incorrect because gastric enzymes like pepsin function within the stomach to begin protein digestion and are not embedded in the microvilli membranes of the small intestine lining. Option c is incorrect because salivary enzymes like salivary amylase are released into the oral cavity to initiate starch digestion and do not operate from the microvilli of the intestine. Option d is incorrect because pancreatic enzymes are secreted by the pancreas into the duodenal lumen and act in the intestinal space, rather than being embedded directly within the microvilli membranes.

Correct Answer: Crypts of Lieberkuhn secreting lysozyme

Option d is correct because crypts of Lieberkuhn are glands located at the base of the intestinal villi that secrete lysozyme, an antimicrobial enzyme protecting the intestinal lining from bacteria. Option a is incorrect because Brunner's glands are found specifically in the duodenum and secrete alkaline mucus to neutralize acidic chyme, serving a protective rather than antimicrobial function. Option b is incorrect because gastric glands are located in the stomach mucosa and secrete hydrochloric acid for protein digestion activation, not antimicrobial enzymes at the base of intestinal villi. Option c is incorrect because salivary glands are located in the oral cavity and secrete amylase for starch digestion, having no presence at the base of villi in the small intestine.

Correct Answer: Secretin

Option b is correct because secretin is released by the duodenum in response to acidic chyme and stimulates the pancreas to secrete bicarbonate ions that neutralize the acid in the small intestine. Option a is incorrect because gastrin is released by G-cells in the stomach to stimulate gastric acid production and enzyme secretion, and it does not trigger pancreatic bicarbonate release. Option c is incorrect because pepsinogen is an inactive enzyme precursor secreted by chief cells in the stomach, not a hormone, and it plays no role in stimulating pancreatic bicarbonate output. Option d is incorrect because insulin is a hormone secreted by beta cells of the pancreatic islets to regulate blood glucose levels and has no role in stimulating bicarbonate secretion for acid neutralization.

Correct Answer: Cholecystokinin

Option c is correct because cholecystokinin, commonly known as CCK, is released by the duodenum in response to fats and proteins and directly stimulates gallbladder contraction to release stored bile. Option a is incorrect because gastrin is a stomach hormone released by G-cells that stimulates gastric acid and enzyme secretion within the stomach, not gallbladder contraction for bile release. Option b is incorrect because secretin is released by the duodenum to stimulate pancreatic bicarbonate secretion for acid neutralization, not gallbladder contraction or bile release into the intestine. Option d is incorrect because pepsin is a protein-digesting enzyme activated in the stomach by hydrochloric acid and is not a hormone capable of signaling the gallbladder to contract.

Correct Answer: Amino acids and monosaccharides

Option a is correct because brush border enzymes break proteins into amino acids and carbohydrates into monosaccharides, which are the simplest absorbable monomers ready to cross the intestinal lining. Option b is incorrect because fatty acids and glycerol are the end products of lipid digestion by lipase enzymes, not the products of brush border enzyme action on proteins and carbohydrates. Option c is incorrect because polypeptides and disaccharides are intermediate breakdown products that still require further enzymatic digestion before they can be absorbed across the intestinal wall. Option d is incorrect because nucleotides are the monomers of nucleic acid digestion, and while glucose is one type of monosaccharide, this pairing does not correctly represent both protein and carbohydrate final products.

Correct Answer: Peritoneum

Option d is correct because the peritoneum is the serous membrane that anchors intestines to the abdominal wall through mesenteries and secretes serous fluid to prevent friction between moving organs. Option a is incorrect because the mucosa is the innermost layer of the alimentary canal wall involved in secretion and absorption within the digestive tube, not abdominal organ anchoring or lubrication. Option b is incorrect because the submucosa is the connective tissue layer within the alimentary canal wall containing blood vessels and nerves, not a membrane that anchors or lubricates abdominal organs. Option c is incorrect because the muscularis externa is the smooth muscle layer within the digestive tract wall responsible for peristalsis and segmentation, not the membrane that anchors and lubricates organs.

Correct Answer: Segmentation

Option b is correct because segmentation involves localized contractions that mix and churn food back and forth within a small intestinal segment, maximizing nutrient contact with the absorptive mucosal surface. Option a is incorrect because peristalsis is the wave-like contraction pattern that propels food forward through the alimentary canal rather than mixing it in place within a localized segment. Option c is incorrect because mass movements are large wave-like contractions found in the large intestine that push fecal contents toward the rectum for elimination rather than mixing nutrients. Option d is incorrect because deglutition is the medical term for the swallowing process, which involves three phases of moving food from the mouth to the stomach, not intestinal mixing contractions.

Correct Answer: Chemical digestion

Option c is correct because chemical digestion is the process where enzymes break covalent bonds in food molecules to produce monomers, fundamentally altering the molecular structure of the nutrients being digested. Option a is incorrect because mechanical digestion physically reduces food particle size through actions like chewing and churning without breaking any molecular bonds or changing the chemical structure of food. Option b is incorrect because propulsion refers to the forward movement of food through the alimentary canal, primarily through peristalsis, and does not involve any enzymatic breakdown of molecular bonds. Option d is incorrect because defecation is the elimination of indigestible waste material from the body through the anus and represents the final stage of the digestive process, not molecular breakdown.

Correct Answer: Peritoneum

Option a is correct because the peritoneum is the serous membrane lining the abdominal cavity that secretes serous fluid, which lubricates the surfaces of organs and prevents painful friction during movement. Option b is incorrect because the muscularis externa is the smooth muscle layer of the alimentary canal that generates peristalsis and segmentation contractions, not a membrane that secretes lubricating fluid. Option c is incorrect because the submucosa is the connective tissue layer within the digestive tract wall that contains blood vessels for nutrient transport, not a membrane producing abdominal lubricating fluid. Option d is incorrect because the mucosa is the innermost lining of the alimentary canal that secretes mucus into the digestive lumen for protection, not the serous fluid that lubricates between abdominal organs.

Correct Answer: Peristalsis

Option d is correct because peristalsis is the coordinated wave-like contraction and relaxation of smooth muscle that propels food forward through the entire length of the alimentary canal from esophagus onward. Option a is incorrect because segmentation is a localized mixing contraction that churns food within a segment to promote digestion and absorption, but does not propel food forward through the tract. Option b is incorrect because absorption is the process of nutrient monomers crossing the intestinal epithelium into the blood or lymph, which is a cellular transport function and not a muscular motility pattern. Option c is incorrect because chemical digestion involves enzymatic breakdown of molecular bonds in food, which is a biochemical process performed by enzymes and not a smooth muscle contraction pattern.