1. Name the 4 layers of the gut wall.
2. What are the 3 components of the mucosa?
3. Complete the following table.
GI Intrinsic Innervation Meissner’s Plexus Auerbach’s Plexus
Location Submucosa Between smooth muscle layers
Function Gut secretion Peristalsis
Input source(s) Autonomic Autonomic
Parasympathetic effects Increase secretion Increase peristalsis
Sympathetic effects Inhibition Inhibition
4. Complete the following table.
Salivary Glands Location Composition and % of
Saliva Volume Parotid Lateral face on surface of masseter All serous; 25% of saliva Submandibular Lower edge of mandible Mixed serous and mucous;
77% of saliva
Sublingual Base of tongue Mixed serous and mucous;
5% of saliva 5. Name the 4 main ionic components of saliva.
mucosa, submucosa, muscularis externa, serosa
epithelium, lamina propria, muscularis mucosa
lipase, amylase, lysozyme, defensins
Gastroenterology Anatomy, Histology, and Physiology
Gastroenterology
6. Name 2 digestive enzymes found in saliva.
7. What nerves control salivary secretions?
8. At what vertebral level does the esophagus traverse the diaphragm?
9. Name 4 narrow points along the length of the esophagus.
10. What is the arrangement of smooth and skeletal muscle in the upper 1/3, middle 1/3, and lower 1/3 of the esophagus?
11. What is characteristic of the epithelial lining of the esophagus?
12. Name the 3 endogenous compounds that stimulate gastric acid secretion.
13. Discuss the stimuli and interaction of the 3 compounds named in the previous question.
14. is a hormone released from gastric and intestinal cells that inhibits gastrin release.
lipase, amylase
parasympathetics
T10
Origin at pharynx, at aortic arch, at left main bronchus, esophageal haitus
Upper: skeletal, middle: skeletal and smooth, lower: smooth
Non-keratinized stratified squamous
Acetylcholine (Ach); gastrin; histamine
Acetylcholine (Ach)—Parasympathetic and enteric. Ach is released in response to the smell of food. In addition, distension of the stomach evokes a reflex (vago-vagal) release of Ach. Ach directly stimulates acid production and indirectly stimulates it by eliciting the release of both histamine and gastrin (distension activates vagus which stimulates the release of gastrin releasing peptide--GRP). Gastrin—
release stimulated by GRP (vagally mediated) and high stomach pH (food entering the stomach increases pH). Histamine—release is stimulated by Ach and gastrin.
Somatostatin
Gastroenterology
15. The pumping of H+ into the lumen is an antiport H+-ATPase. is the ion that antiports with H+.
16. In addition to H+, and are secreted into the lumen of the stom- ach, thus making stomach secretions high in these electrolytes.
17. Discuss what is meant by “alkaline tide.”
18. Indicate the 2 mechanisms by which drugs inhibit acid secretion by parietal cells.
19. and are required for complete
fat digestion and absorption.
20. Name the 3 primary end products of carbohydrate digestion and the mechanism of absorption for each.
21. Protein digestion begins in the via the enzyme . Potassium
Potassium chloride
The alkaline tide refers to the rise in pH of the blood draining the stomach during high rates of acid secretion. The proton that is secreted into the lumen comes from the combination of CO2 and water.
The bicarbonate that results from this reaction is then transported from the parietal cell into the blood in exchange for chloride.
Proton pump inhibitors, i.e., omeprazole, block the H—K+ antiporter on the luminal membrane. Histamine (H2) receptor blockers, i.e., cimetidine, block histamine-induced acid secretion.
Bile salts pancreatic lipases
The three end products are glucose, galactose, and fructose. Digestion begins at the mouth with salivary amylase and continues in the small intestine with pancreatic amylase. Brush border enzymes breakdown disaccharides into the monosaccharides. Glucose and galactose are absorbed via a secondary active transport coupled to Na+. Fructose is absorbed via facilitated transport.
Stomach pepsin
Gastroenterology Anatomy, Histology, and Physiology
Gastroenterology
23. Discuss the mechanism for the absorption of the end products of protein digestion.
24. The secretion of causes Na+ and water to enter the lumen of the small intestine and is important for maintaining adequate hydration of the chyme.
25. Bicarbonate secretion begins in the , which is also the site of bile salt and B12 absorption.
26. Fill in the table below for the key GI hormones.
Hormone Source Stimulus Action
CCK Duodenum Fats/AA Pancreatic enzyme secretion; Gall
bladder contraction; Relax sphincter of Oddi; ↓ gastric motility
Gastrin Stomach; duodenum GRP (second to vagal
stimulation) Stimulates acid secretion
GIP Duodenum Fats/AA/CHO ↓ gastric motility; ↑ insulin secretion
Motilin Duodenum; jejunum >2 hrs fasting Migrating motility complex; Erythro- mycin is a motilin agonist
Secretin Duodenum Acid Pancreatic bicarbonate secretion;
↓ gastric motility 27. What are 2 types of diaphragmatic hernias seen in adults?
28. What type of inguinal hernia passes through Hesselbach’s triangle, and what type passes outside of it?
Proteins are absorbed as amino acids, di- and tripeptides. These are absorbed in symport with either Na+ or H+ (secondary active transport).
Chloride
ileum
Sliding hiatal hernia and paraesophageal hernia
Indirect hernia passes outside Hesselbach’s triangle (lateral to inferior epigastric vessels) and direct
Gastroenterology