Digestive System Flashcards
1
Q
What is the primary function of the digestive system?
A
To break down food into nutrients for absorption and eliminate waste.
2
Q
What is the difference between mechanical and chemical digestion?
A
Mechanical digestion involves physical breakdown (e.g., chewing), while chemical digestion involves enzymatic breakdown.
3
Q
What structures comprise the alimentary canal?
A
Oral cavity, esophagus, stomach, small intestine, large intestine, anus.
4
Q
What are the associated digestive organs?
A
Teeth, tongue, salivary glands, pancreas, liver, gallbladder.
5
Q
What are the three layers of the mucosa in the digestive tract?
A
Epithelium, lamina propria, muscularis mucosae.
6
Q
What are the two types of epithelium found in the digestive system?
A
Stratified squamous (protective regions) and simple columnar (absorptive/secreting regions).
7
Q
What are the four major layers of the gastrointestinal tract?
A
Mucosa, submucosa, muscularis externa, serosa/adventitia.
8
Q
How does the muscularis externa differ in different digestive organs?
A
It consists of smooth muscle but has striated muscle in the esophagus and anal canal.
9
Q
What role does the submucosal plexus (Meissner’s plexus) play?
A
Regulates secretion and blood flow in the GI tract.
10
Q
What is the function of the myenteric plexus (Auerbach’s plexus)?
A
Controls peristalsis and muscular contractions of the gut.
11
Q
Which organ secretes bile and what is its function?
A
The liver secretes bile, which emulsifies fats for digestion.
12
Q
What is the primary function of the esophagus?
A
To transport food from the oral cavity to the stomach.
13
Q
How does the stomach facilitate digestion?
A
Through mechanical churning, acid secretion, and enzymatic breakdown of proteins.
14
Q
Which hormone stimulates acid secretion in the stomach?
A
Gastrin, released by enteroendocrine cells in the stomach.
15
Q
What prevents the stomach from digesting itself?
A
A mucus layer rich in bicarbonate that neutralizes acid at the epithelial surface.
16
Q
What are the primary functions of the liver?
A
Bile production, detoxification, metabolism, protein synthesis, and storage of nutrients.
17
Q
What structures make up a hepatic lobule?
A
Central vein, hepatocyte plates, sinusoids, Kupffer cells, and the portal triad.
18
Q
What is the significance of the hepatic portal vein?
A
It transports nutrient-rich blood from the intestines to the liver for processing.
19
Q
How do hepatocytes contribute to metabolism?
A
They process nutrients, detoxify blood, synthesize proteins, and store glycogen.
20
Q
What is the function of the gallbladder?
A
To store and concentrate bile before releasing it into the duodenum.
21
Q
What stimulates the gallbladder to release bile?
A
Cholecystokinin (CCK), released by the small intestine when fatty food is present.
22
Q
How does the pancreas function in digestion?
A
The exocrine pancreas secretes digestive enzymes, and the endocrine pancreas regulates blood sugar.
23
Q
Which pancreatic enzymes digest proteins?
A
Trypsin, chymotrypsin, and carboxypeptidase.
24
Q
Which pancreatic enzymes digest carbohydrates and lipids?
A
Amylase (carbohydrates) and lipase (lipids).
25
What is the function of bicarbonate secreted by the pancreas?
To neutralize acidic chyme entering the small intestine.
26
What is the role of the small intestine in digestion?
Completes digestion and absorbs nutrients into the bloodstream.
27
What structures increase the surface area of the small intestine?
Plicae circulares, villi, and microvilli.
28
Which enzyme activates pancreatic zymogens?
Enteropeptidase, which converts trypsinogen into trypsin.
29
What is the function of Peyer’s patches in the ileum?
They are lymphoid nodules that protect against pathogens in the gut.
30
What is the main function of the large intestine?
Absorbs water and electrolytes, compacts feces, and houses gut microbiota.
31
What are haustra?
Sacculations of the colon formed by contractions of the teniae coli.
32
How does the appendix contribute to the immune system?
Contains lymphoid tissue that may help regulate gut bacteria.
33
What are the two types of muscle movement in the intestines?
Peristalsis (propulsion) and segmentation (mixing).
34
What are the three phases of gastric secretion?
Cephalic phase (brain response), gastric phase (stomach response), and intestinal phase (duodenal response).
35
How is glucose absorbed in the intestines?
Via sodium-glucose cotransporters (SGLT) on enterocytes.
36
Which structures form the portal triad in the liver?
A branch of the hepatic artery, portal vein, and bile duct.
37
What are the functions of Kupffer cells?
Phagocytosis of pathogens, debris, and aged red blood cells in liver sinusoids.
38
What is the role of bile salts in fat digestion?
They emulsify fats, making them accessible to lipases.
39
What is the difference between exocrine and endocrine pancreatic function?
Exocrine secretes digestive enzymes, endocrine regulates blood sugar (insulin and glucagon).
40
What causes jaundice?
Accumulation of bilirubin due to liver dysfunction or bile duct obstruction.
41
What are the main products of carbohydrate digestion?
Monosaccharides: glucose, fructose, and galactose.
42
What causes gastroesophageal reflux disease (GERD)?
Weakening of the lower esophageal sphincter, allowing acid reflux.
43
How does the gut microbiota contribute to digestion?
Produces short-chain fatty acids, synthesizes vitamins, and aids in immune regulation.
44
What is the function of the anal sphincters?
Internal sphincter (involuntary) and external sphincter (voluntary) control defecation.
45
What is the function of somatostatin in digestion?
Inhibits gastric secretion, bile release, and pancreatic enzyme secretion.
46
Which vitamins are absorbed in the large intestine?
Vitamin K and some B vitamins, produced by gut bacteria.
47
What is the function of chylomicrons?
Transport dietary lipids from the intestines to the lymphatic system.
48
What is the significance of the intrinsic factor secreted by the stomach?
Essential for vitamin B12 absorption in the ileum.
49
What is lactose intolerance?
Deficiency in lactase enzyme, leading to undigested lactose causing gastrointestinal symptoms.
50
What is celiac disease?
An autoimmune reaction to gluten that damages the small intestine's villi, reducing nutrient absorption.
51
What is the function of secretin?
Stimulates bicarbonate secretion from the pancreas to neutralize stomach acid.
52
Describe the detailed mechanism by which parietal cells secrete hydrochloric acid.
HCl secretion involves carbonic anhydrase converting CO2 and H2O into H2CO3, which dissociates into H+ and HCO3-. The H+/K+ ATPase pump actively transports H+ into the lumen in exchange for K+, while Cl- follows passively, forming HCl.
53
Explain the role of the enteric nervous system (ENS) in coordinating peristalsis.
The ENS regulates peristalsis through sensory neurons detecting stretch, interneurons processing signals, and motor neurons stimulating excitatory contraction (ACh) proximal to the bolus and inhibitory relaxation (NO) distal to the bolus.
54
What is the role of interstitial cells of Cajal in gastrointestinal motility?
They act as pacemakers in the GI tract, generating slow-wave potentials that coordinate smooth muscle contractions for peristalsis and segmentation.
55
Why does the liver receive both oxygenated and deoxygenated blood?
The hepatic artery supplies oxygen-rich blood, while the portal vein supplies nutrient-rich, deoxygenated blood for metabolic processing and detoxification.
56
Describe the enterohepatic circulation of bile salts.
Bile salts are secreted into bile, emulsify fats in the duodenum, are reabsorbed in the ileum via active transport, and return to the liver via the portal vein for reuse.
57
What molecular mechanism allows the stomach to withstand a pH of 1-2?
Tight junctions between epithelial cells prevent acid penetration, mucus with bicarbonate creates a protective pH gradient, and rapid epithelial turnover (every 3-5 days) replaces damaged cells.
58
How does pancreatic secretion adapt to varying dietary compositions?
CCK stimulates enzyme-rich secretion in response to fats and proteins, secretin triggers bicarbonate secretion in response to acid, and neural reflexes fine-tune secretion.
59
Why are zymogens secreted in an inactive form, and how are they activated?
Prevents autodigestion of the pancreas; trypsinogen is activated by enteropeptidase in the duodenum, which then activates other proteases.
60
How does the gut microbiota influence host metabolism?
Gut bacteria ferment fiber into short-chain fatty acids, regulate bile acid metabolism, influence insulin sensitivity, and modulate immune responses.
61
What is the molecular mechanism behind lactose intolerance?
Lactase deficiency prevents lactose hydrolysis into glucose and galactose, leading to osmotic diarrhea and bacterial fermentation causing gas and bloating.
62
How does vitamin B12 absorption depend on gastric and intestinal function?
Parietal cells secrete intrinsic factor, which binds B12; the complex is absorbed in the ileum via receptor-mediated endocytosis.
63
What is the role of the SGLT1 transporter in intestinal glucose absorption?
SGLT1 uses sodium gradients (Na+/K+ ATPase) to actively transport glucose into enterocytes, followed by GLUT2-mediated diffusion into the blood.
64
Describe the structural and functional differences between villi and microvilli.
Villi are macroscopic projections with blood/lymphatic vessels, while microvilli are microscopic actin-based structures forming the brush border, containing digestive enzymes.
65
What is the role of FXR (farnesoid X receptor) in bile acid homeostasis?
FXR activation in hepatocytes inhibits bile acid synthesis and enhances their enterohepatic recirculation to prevent bile acid toxicity.
66
How does ethanol metabolism contribute to fatty liver disease?
Ethanol is metabolized by alcohol dehydrogenase and CYP2E1, producing NADH, which inhibits β-oxidation and promotes fatty acid accumulation.
67
Explain the histological changes seen in Barrett’s esophagus.
Chronic acid reflux induces metaplasia, replacing nonkeratinized stratified squamous epithelium with columnar epithelium with goblet cells.
68
Why does gastric bypass surgery reduce appetite beyond mechanical restriction?
It alters gut hormone secretion (increased GLP-1, PYY), reducing hunger and enhancing insulin sensitivity.
69
What role do bile acids play in cholesterol homeostasis?
They are synthesized from cholesterol, regulate FXR, inhibit HMG-CoA reductase, and promote cholesterol excretion in bile.
70
Why is the jejunum the primary site of nutrient absorption?
It has the highest density of plicae circulares, villi, and transporters for monosaccharides, amino acids, and lipids.
71
How do Peyer’s patches influence immune tolerance in the gut?
They sample antigens, promote regulatory T-cell differentiation, and induce IgA production for mucosal immunity.
72
What triggers the migrating motor complex (MMC) in fasting conditions?
Motilin secretion stimulates periodic contractions to clear debris and bacteria from the small intestine.
73
How does the gut-brain axis regulate digestion?
Neural (vagus nerve) and hormonal signals (ghrelin, CCK) coordinate appetite, motility, and enzyme secretion.
74
Describe the mechanisms of bile acid malabsorption.
Diseases like Crohn’s reduce ileal reabsorption, leading to diarrhea and increased bile acid synthesis by the liver.
75
What causes pernicious anemia?
Autoimmune destruction of parietal cells reduces intrinsic factor secretion, leading to vitamin B12 deficiency and megaloblastic anemia.
76
How do enterochromaffin-like (ECL) cells contribute to acid secretion?
They release histamine, which activates H2 receptors on parietal cells, increasing cAMP and HCl production.
77
What is the role of Paneth cells in gut immunity?
They secrete antimicrobial peptides like defensins and lysozyme to regulate gut microbiota.
78
How do secretin and cholecystokinin (CCK) work together in digestion?
Secretin triggers bicarbonate secretion, while CCK stimulates pancreatic enzyme release and gallbladder contraction.
79
What factors regulate iron absorption in the duodenum?
Hepcidin regulates ferroportin, reducing iron export when levels are high; vitamin C enhances iron uptake by reducing Fe3+ to Fe2+.
80
81
What are the main functions of the digestive system?
Ingestion, digestion, motility, secretion, absorption, hormone release, elimination, immune defense.
82
Which layers make up the general structure of the gastrointestinal tract?
Mucosa, submucosa, muscularis externa, serosa/adventitia.
83
What are the primary functions of the small intestine?
Digestion via enzymes, absorption of ~90% of nutrients, water, and electrolytes.
84
What is the role of the myenteric (Auerbach’s) plexus in digestion?
Regulates peristalsis and the rhythmic contraction of the muscularis externa.
85
How does the stomach protect itself from acid-induced damage?
Mucus secretion with bicarbonate ions, tight junctions between cells, rapid cell turnover.
86
What are the differences between the four types of lingual papillae?
Filiform (mechanical, no taste buds), Fungiform (mushroom-shaped, taste buds), Foliate (ridges on lateral tongue, taste buds), Circumvallate (largest, taste buds on sides, von Ebner's glands).
87
How do parietal cells contribute to digestion?
Secrete hydrochloric acid (HCl) and intrinsic factor, essential for vitamin B12 absorption.
88
What is the function of the crypts of Lieberkühn in the small intestine?
Secrete enzymes, house stem cells for epithelial renewal, produce antimicrobial substances.
89
Which glands produce digestive enzymes in the pancreas?
Exocrine pancreas: acinar cells secrete amylase, lipase, proteases (trypsinogen, chymotrypsinogen).
90
How does bile aid in fat digestion?
Emulsifies fats into micelles, allowing pancreatic lipase to break them into monoglycerides and fatty acids.
91
What structures increase the absorptive surface area in the small intestine?
Plicae circulares, villi, microvilli.
92
How is glucose absorbed in the small intestine?
Via sodium-glucose co-transporters (SGLT) on enterocytes, then facilitated diffusion into capillaries.
93
What is the function of the hepatic portal vein?
Carries nutrient-rich, oxygen-depleted blood from the digestive tract to the liver for processing.
94
What are the structural components of a hepatic lobule?
Hexagonal plates of hepatocytes, central vein, portal triads, sinusoids, space of Disse.
95
How does the gallbladder concentrate bile?
By removing water and electrolytes through active transport by its epithelial cells.
96
What are Kupffer cells and their function?
Specialized macrophages in liver sinusoids, phagocytose old erythrocytes and pathogens.
97
How do chief cells contribute to digestion?
Secrete pepsinogen, which is activated into pepsin by HCl to digest proteins.
98
What is the role of enteroendocrine cells in digestion?
Secrete hormones like gastrin (stimulates acid secretion), secretin (stimulates bicarbonate), and cholecystokinin (stimulates bile release).
99
How is peristalsis regulated?
By the enteric nervous system, particularly the myenteric plexus, under autonomic nervous system influence.
100
What is Barrett’s esophagus and its significance?
Metaplastic transformation of esophageal epithelium due to acid reflux, increasing cancer risk.
