Which layer of the alimentary canal wall contains the myenteric plexus, positioned between its inner circular and outer longitudinal smooth muscle?
Muscularis
✓
Mucosa
Submucosa
Serosa
Correct Answer
Muscularis
The muscularis is the layer of smooth muscle that moves material through the tract, and the myenteric plexus lies between its circular and longitudinal sheets to control motility. The mucosa is the innermost lining of epithelium, lamina propria and muscularis mucosae. The submucosa holds the submucosal plexus along with blood and lymphatic vessels. The serosa is the outer serous membrane covering intraperitoneal organs.
Category: GI Tract Overview
Question 2
Which cells of the gastric glands secrete hydrochloric acid into the stomach lumen?
Chief cells
Parietal cells
✓
Mucous neck cells
G cells
Correct Answer
Parietal cells
Parietal cells pump hydrogen ions and secrete chloride, forming the hydrochloric acid that makes gastric juice strongly acidic. Chief cells secrete pepsinogen and gastric lipase. Mucous neck cells secrete a thin, acidic mucus. G cells release the hormone gastrin into the blood.
Category: The Stomach
Question 3
Which inactive enzyme do chief cells secrete that is converted by acid into an active protein-digesting enzyme?
Intrinsic factor
Gastrin
Pepsinogen
✓
Trypsinogen
Correct Answer
Pepsinogen
Chief cells release pepsinogen, which hydrochloric acid converts to pepsin, the stomach's main protease. Intrinsic factor comes from parietal cells and is needed for vitamin B12 absorption. Gastrin is a hormone made by G cells. Trypsinogen is a pancreatic proenzyme activated in the small intestine.
Category: The Stomach
Question 4
Which enzyme in saliva begins the chemical digestion of starch in the mouth?
Pepsin
Trypsin
Lactase
Salivary amylase
✓
Correct Answer
Salivary amylase
Salivary amylase breaks starch into smaller carbohydrate fragments while food is still being chewed. Pepsin is a gastric protease. Trypsin is a pancreatic protease that acts in the small intestine. Lactase is a brush border enzyme that splits lactose.
Category: Mouth and Esophagus
Question 5
Acidic chyme entering the duodenum triggers the release of which hormone that stimulates the pancreas to secrete bicarbonate-rich juice?
Secretin
✓
Gastrin
Cholecystokinin
Ghrelin
Correct Answer
Secretin
Secretin is released by the duodenum in response to acid and signals the pancreas to release bicarbonate, which neutralizes chyme. Gastrin is a stomach hormone that stimulates gastric acid secretion. Cholecystokinin mainly triggers gallbladder contraction and enzyme-rich pancreatic secretion in response to fats and proteins. Ghrelin is a stomach hormone associated with hunger.
Category: Digestive Regulation
Question 6
Fats and proteins arriving in the duodenum trigger which hormone that causes the gallbladder to contract and release bile?
Secretin
Cholecystokinin
✓
Gastrin
Glucagon
Correct Answer
Cholecystokinin
Cholecystokinin is released by the duodenum and causes the gallbladder to contract and the pancreas to release digestive enzymes. Secretin chiefly stimulates bicarbonate secretion from the pancreas. Gastrin stimulates gastric acid secretion and stomach motility. Glucagon is a pancreatic islet hormone that raises blood glucose.
Category: Digestive Regulation
Question 7
Which pancreatic proenzyme is activated by the brush border enzyme enteropeptidase?
Pepsinogen
Chymotrypsinogen
Trypsinogen
✓
Procarboxypeptidase
Correct Answer
Trypsinogen
Enteropeptidase on the intestinal brush border converts trypsinogen into trypsin. Pepsinogen is a gastric proenzyme activated by hydrochloric acid. Chymotrypsinogen is activated by trypsin. Procarboxypeptidase is also activated by trypsin.
Category: Chemical Digestion
Question 8
Which segment of the small intestine is the main site for absorbing vitamin B12 and recycling bile salts?
Duodenum
Jejunum
Cecum
Ileum
✓
Correct Answer
Ileum
The ileum is the final and longest segment of the small intestine, and it absorbs vitamin B12 and bile salts. The duodenum is the short first segment that receives chyme, bile and pancreatic juice. The jejunum is the middle segment. The cecum is the first part of the large intestine.
Category: Small and Large Intestines
Question 9
Which sphincter regulates the passage of material from the small intestine into the large intestine?
Ileocecal sphincter
✓
Pyloric sphincter
Lower esophageal sphincter
Internal anal sphincter
Correct Answer
Ileocecal sphincter
The ileocecal sphincter lies where the ileum joins the cecum and controls movement into the large intestine. The pyloric sphincter controls flow from the stomach into the duodenum. The lower esophageal sphincter guards the entrance to the stomach. The internal anal sphincter is an involuntary smooth muscle sphincter at the anus.
Category: Small and Large Intestines
Question 10
Which liver cells, found within the sinusoids, phagocytose worn-out blood cells and bacteria?
Hepatocytes
Kupffer cells
✓
Goblet cells
Parietal cells
Correct Answer
Kupffer cells
Kupffer cells are phagocytic reticuloendothelial cells located within the liver sinusoids that remove old blood cells, bacteria and debris. Hepatocytes are the main liver cells that produce bile and process nutrients. Goblet cells secrete mucus in the intestinal lining. Parietal cells are gastric gland cells that secrete acid.
Category: Accessory Organs
Question 11
What do bile salts do to large lipid globules in the small intestine?
Hydrolyze them into fatty acids
Package them into chylomicrons
Emulsify them into smaller droplets
✓
Carry them into the lymph
Correct Answer
Emulsify them into smaller droplets
Bile salts emulsify fat, breaking large globules into small droplets and greatly increasing the surface area for lipase. Hydrolyzing triglycerides into fatty acids is the work of lipase, not bile. Packaging lipids into chylomicrons happens inside absorptive epithelial cells. Carrying lipids into the lymph is done by chylomicrons entering lacteals.
Category: Accessory Organs
Question 12
After being assembled in intestinal absorptive cells, chylomicrons leave the villus by entering which structure?
Hepatic portal vein
Blood capillary
Common bile duct
Lacteal
✓
Correct Answer
Lacteal
Chylomicrons are too large to enter blood capillaries, so they pass into the lacteal, a lymphatic capillary in each villus, and reach the blood later through the thoracic duct. The hepatic portal vein carries absorbed water-soluble nutrients to the liver. Blood capillaries absorb monosaccharides and amino acids. The common bile duct carries bile toward the duodenum.
Category: Chemical Digestion
Question 13
During which stage of swallowing does the tongue push the bolus back into the oropharynx under conscious control?
Voluntary phase
✓
Pharyngeal phase
Esophageal phase
Cephalic phase
Correct Answer
Voluntary phase
In the voluntary phase, the tongue consciously pushes the bolus toward the oropharynx. The pharyngeal phase is the involuntary reflex in which the airway closes as the bolus passes the pharynx. The esophageal phase is involuntary peristalsis carrying the bolus to the stomach. The cephalic phase is a stage of gastric secretion, not swallowing.
Category: Mouth and Esophagus
Question 14
How many teeth make up a complete set of permanent adult teeth?
20
32
✓
28
36
Correct Answer
32
A full permanent set has 32 teeth, including the third molars. The number 20 is the count of deciduous, or baby, teeth. The number 28 is the count without the four wisdom teeth, not the complete set. The number 36 exceeds the normal human dentition.
Category: Mouth and Esophagus
Question 15
Which phase of gastric secretion begins before food reaches the stomach, triggered by the sight, smell, taste or thought of food?
Gastric phase
Intestinal phase
Cephalic phase
✓
Absorptive phase
Correct Answer
Cephalic phase
The cephalic phase is driven by the brain through the vagus nerve and prepares the stomach before food arrives. The gastric phase begins once food distends the stomach and raises its pH. The intestinal phase begins as chyme enters the duodenum. Absorptive phase is not one of the three phases of gastric secretion.
Category: The Stomach
Question 16
Which movement of the small intestine mixes chyme with digestive juices by localized contractions of circular muscle without strongly propelling it forward?
Peristalsis
Mass movement
Haustral contraction
Segmentation
✓
Correct Answer
Segmentation
Segmentation is a back-and-forth churning produced by rings of circular muscle contracting in alternating segments, which mixes chyme and exposes it to the absorptive surface. Peristalsis is a wave of contraction that pushes contents forward. Mass movements are strong waves that sweep contents through the colon. Haustral contractions occur in the large intestine, not the small intestine.
Category: Digestive Processes
Question 17
Bacteria in the large intestine synthesize which vitamin that the body uses for blood clotting?
Vitamin K
✓
Vitamin C
Vitamin A
Vitamin D
Correct Answer
Vitamin K
Colon bacteria produce vitamin K, which the liver needs to make several clotting factors. Vitamin C comes from the diet and supports collagen synthesis. Vitamin A comes from the diet and is needed for vision. Vitamin D is made in the skin with sunlight exposure and supports calcium absorption.
Category: Small and Large Intestines
Question 18
Which pancreatic cells produce the digestive enzymes of pancreatic juice?
Alpha cells
Acinar cells
✓
Beta cells
Delta cells
Correct Answer
Acinar cells
Acinar cells form the exocrine part of the pancreas and secrete the enzymes of pancreatic juice into ducts leading to the duodenum. Alpha cells are islet cells that secrete glucagon. Beta cells are islet cells that secrete insulin. Delta cells are islet cells that secrete somatostatin.
Category: Accessory Organs
Question 19
Lactase splits lactose into which pair of monosaccharides?
Glucose and fructose
Two glucose molecules
Glucose and galactose
✓
Galactose and fructose
Correct Answer
Glucose and galactose
Lactase is a brush border enzyme that breaks lactose into one glucose and one galactose. Glucose and fructose are the products of sucrase acting on sucrose. Two glucose molecules are the products of maltase acting on maltose. Galactose and fructose are not the units of any common dietary disaccharide.
Category: Chemical Digestion
Question 20
Which enzyme carries out most of the digestion of dietary triglycerides?
Lingual lipase
Pepsin
Pancreatic amylase
Pancreatic lipase
✓
Correct Answer
Pancreatic lipase
Pancreatic lipase, working on emulsified fat in the small intestine, digests most triglycerides into free fatty acids and monoglycerides. Lingual lipase begins a small amount of fat digestion that continues in the stomach. Pepsin digests proteins. Pancreatic amylase digests starch.
Category: Chemical Digestion