MLT GlobePhysiology: Digestive physiology & nutrition
28 Physiology MCQs on Digestive physiology & nutrition with answers and explanations.
Taking food and drink into the mouth is termed:
Ingestion is the intake of food and fluids. Propulsion moves food along the gut, digestion breaks it down, and absorption takes nutrients into the blood.
What is the overall effect of vagal (parasympathetic) stimulation on the digestive tract?
Parasympathetic activity promotes 'rest and digest': it increases peristalsis and secretion and relaxes sphincters. Sympathetic activity does the reverse.
A patient complains that food 'sticks' when she tries to swallow. The medical term for this symptom is:
Dysphagia means difficulty in swallowing. Haematemesis is vomiting blood, melaena is black tarry stool from upper GI bleeding, and nausea is a feeling of sickness.
Which gastric gland cells release the inactive enzyme precursor pepsinogen?
Chief cells secrete pepsinogen, activated to pepsin by HCl. Parietal cells secrete HCl and intrinsic factor; G cells release gastrin.
Which type of meal delays gastric emptying the most?
Fat in the duodenum releases CCK and other signals that strongly slow gastric emptying, so fatty meals stay in the stomach longest. Liquids and carbohydrates leave fastest.
Gastric secretion starting at the sight, smell or thought of food, before food reaches the stomach, is the:
The cephalic phase is the first phase, driven by the vagus nerve in response to sensory cues and anticipation of food. The gastric phase starts when food distends the stomach.
The hepatopancreatic sphincter (sphincter of Oddi) controls the flow of bile and pancreatic juice into the:
The sphincter of Oddi surrounds the hepatopancreatic ampulla where the bile and pancreatic ducts open into the second part of the duodenum. CCK relaxes it.
Pepsin, activated from pepsinogen by stomach acid, starts the digestion of:
Pepsin is an endopeptidase that cleaves proteins into polypeptides. Fats are digested mainly by pancreatic lipase and carbohydrates by amylases.
Peyer's patches, aggregated lymphoid follicles in the gut wall, are most numerous in the:
Peyer's patches are concentrated in the ileum, where they sample gut antigens via M cells. The duodenum and jejunum have only scattered solitary follicles.
Which inactive enzyme is present in pancreatic juice and is activated by enterokinase in the duodenum?
Enteropeptidase (enterokinase) converts trypsinogen to trypsin, which activates other pancreatic zymogens. Pepsinogen and intrinsic factor are gastric; CCK is a duodenal hormone.
Which vitamin is carried in chylomicrons into the intestinal lacteals rather than directly into portal blood?
Fat-soluble vitamins (A, D, E, K) are packed into chylomicrons and enter lacteals. Water-soluble vitamins such as C, thiamine and folate go into portal capillaries.
A hormone released by G cells of the gastric antrum is chemically classed as a peptide. Which hormone is it?
Gastrin is a peptide hormone that stimulates acid secretion. Aldosterone is a steroid, prostaglandins are eicosanoids, and serotonin is an amine derived from tryptophan.
A patient complains of excess intestinal gas and frequent passing of wind. Which term describes this?
Flatulence refers to excessive gas in the digestive tract. Impaction is hardened retained stool, nocturia is night-time urination and dysphagia is difficulty swallowing.
A patient with iron deficiency after gastric bypass surgery has lost the main site of dietary iron absorption. Which segment is this?
Non-haem iron is absorbed mainly in the duodenum (and proximal jejunum) via DMT1. Bypassing the duodenum is a common cause of post-bariatric iron deficiency.
Under the WHO adult classification, obesity is defined as a body mass index of:
BMI ≥30 is obesity, 25–29.9 overweight, 18.5–24.9 normal and below 18.5 underweight.
Which digestive secretion contains no digestive enzymes, yet is essential for fat digestion?
Bile salts emulsify fats and form micelles but do not hydrolyse anything. Saliva contains amylase and gastric juice contains pepsin.
Which statement about the muscularis externa of the gut is correct?
Circular muscle is inner and longitudinal is outer, with the myenteric plexus between them. Sphincters are thickened circular muscle, and peristalsis needs coordination of both layers.
Acid chyme entering the duodenum releases secretin. This belongs to which phase of gastric secretion control?
Secretin is released by duodenal S cells in response to acid in the intestinal phase. It stimulates bicarbonate-rich pancreatic juice and inhibits gastric secretion.
Loss of which gastric cells, as in autoimmune gastritis, leads to vitamin B12 deficiency?
Parietal cells secrete intrinsic factor, needed for B12 absorption in the terminal ileum. Their destruction causes pernicious anaemia with megaloblastic changes.
The epithelial lining of the small intestine is completely renewed approximately every:
Crypt stem cells divide constantly and cells migrate to the villus tips, where they are shed within about 3-5 days. That is why the gut mucosa is sensitive to chemotherapy.