Gastrointestinal Physiology Overview

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Questions and Answers

What is the primary secretion of the G Cell located in the antrum of the stomach?

Gastrin (correct)

Histamine

Somatostatin

Mucus

Which of the following cells is responsible for secreting hydrochloric acid and intrinsic factor in the stomach?

Chief Cell

Mucous Cell

ECL Cell

Parietal Cell (correct)

Which secretion primarily assists in the digestion of collagen found in meat?

Pepsinogen (correct)

Histamine

Mucus

Somatostatin

What mechanism primarily allows parietal cells to move hydrogen ions into the gastric lumen?

Primary active transport Signup and view all the answers

Which of the following best describes the role of somatostatin released by D Cells?

Inhibits gastric acid secretion Signup and view all the answers

Which cell type is responsible for secreting pepsinogen in the stomach?

Chief Cell Signup and view all the answers

What mechanism protects the gastric mucosa from acid and pepsin?

Tight junctions between epithelial cells Signup and view all the answers

Which hormone stimulates the secretion of gastric acid in the stomach?

Gastrin Signup and view all the answers

What is one of the effects of chronic use of NSAIDs on the gastric mucosal barrier?

Dissolution of the protective barrier Signup and view all the answers

What is the primary function of H2 receptor antagonists in gastric secretion regulation?

Decreases gastric acid secretion Signup and view all the answers

Which of the following contributes to the neutralization of gastric acids in the stomach lumen?

Bicarbonate ions Signup and view all the answers

What physiological process allows the stomach to increase its volume to accommodate food?

Receptive relaxation Signup and view all the answers

Which cell type secretes histamine, a key component in gastric secretion regulation?

ECL Cell Signup and view all the answers

Which hormone is primarily responsible for stimulating the secretion of gastric acid in the stomach?

Gastrin Signup and view all the answers

What is the primary function of the gastric mucosal barrier?

To prevent damage from hydrochloric acid Signup and view all the answers

What type of cells are primarily responsible for secreting pepsinogen in the stomach?

Chief cells Signup and view all the answers

How is hydrochloric acid (HCl) secreted by the gastric parietal cells typically stimulated?

Through the action of histamine on H2 receptors Signup and view all the answers

What role does pepsin play in digestion?

It breaks down proteins into peptides Signup and view all the answers

Which factor is NOT involved in the regulation of gastric cell secretion?

Serum calcium levels Signup and view all the answers

The secretion of which substance is stimulated by the presence of fatty acids in the small intestine?

Cholecystokinin (CCK) Signup and view all the answers

Which of the following is a mechanism through which acid secretion in the stomach can be inhibited?

Action of somatostatin Signup and view all the answers

Study Notes

Gastrointestinal Physiology Lectures

GI system overview covers Mouth, Pharynx, Salivary glands, Esophagus, Stomach, Intestines, Pancreas, Liver, and Gallbladders
Lecture 3 covers digestion and absorption of carbohydrates, proteins, and fats
Overview of GI processes includes motility, secretion, digestion, and absorption
The GI tract's motility includes mixing and churning (segmentation) and propulsion (peristalsis)
Secretion and absorption involves 1200ml water/day and 800g solids/day ingested, with 1500ml salivary secretions, 2000ml gastric secretions, 500ml bile, 1500ml pancreatic secretions, and 1500ml intestinal secretions.
Digestion and absorption processes include digestion of polysaccharides, disaccharides, proteins, fats, mineral ions, and water.
Absorption involves active transport, osmosis, diffusion, and secretion to the liver and thoracic duct using a lacteal
GI tract anatomy (I) includes the structure of the stomach and intestines, showing esophageal, stomach, pyloric sphincter, and intestinal parts for both upper and lower tract
GI tract anatomy (II) examines the stomach wall and intestinal wall, demonstrating internal structures like epithelial layers, lamina propria, and muscularis (with both circular and longitudinal muscle layers)
Oral cavity and esophagus involves swallowing (chewing and swallowing, saliva, and minimal carbs and fats)
Saliva functions include lubrication, buffering, partial digestion, cleaning teeth, and tasting.
Salivary glands secrete 1500ml saliva/day with parotid (25%), submandibular (70%), and sublingual (5%).
Salivary gland structure includes acinar and ductal cells; acinar cells produce mucous or serous fluids (enzymes) and ductal cells control fluid secretion and ion modification.
Decreased saliva production can result from extended methamphetamine use or autoimmune disorders like Sjögren's syndrome.
Regulation of salivary secretion is mainly neuronal with parasympathetic and sympathetic stimulation increasing blood flow to glands and low secretion for mouth moisture. The cephalic phase of secretion occurs with smell or sight of food.
Swallowing (deglutition) is a reflex pushing food/liquid into the esophagus and involves three phases: oral, pharyngeal, and esophageal.
Oral phase involves pushing bolus against soft palate.
Pharyngeal phase involves soft palate elevation, upper esophageal sphincter relaxation, and epiglottis closing.
Esophageal phase involves peristaltic waves (and gravity) downward food movement

Stomach

Stomach functions include storage, mechanical/chemical digestion, and protection (from bacteria).
Stomach anatomy includes parts like the esophagus, lower esophageal sphincter, body (secreting mucus, pepsinogen, and HCI), duodenum, fundus, and antrum.
Specialized cells in the stomach synthesize/secrete mucus, enzymes (precursors), hydrochloric acid, and hormones.
Stomach cells (like parietal, chief, mucous, ECL, D, and G cells) have specific secretions (HCI, IF, pepsinogen, mucus, histamine, somatostatin, and gastrin) for different destinations (lumen, mucosa, or blood).
The mechanism of acid secretion in parietal cells involves carbonic anhydrase, primary active transport, and regulation by gastrin, histamine, and somatostatin.
The chief cell plays a role in pepsin activity, where inactive pepsinogen is converted to active pepsin by low pH, crucial for digesting proteins
Gastric mucosal barrier (1 & 2) protects the stomach lining from acid and pepsin and has layers of mucous cells, specialized epithelial cells, and bicarbonate ions to neutralize acids.
Hormonal regulation in the stomach involves gastrin, CCK, secretin, and GIP, influencing acid secretion and motility

Stomach Motility

Stomach motility (1) includes receptive relaxation, allowing increased volume (50ml to 1500ml).
Stomach motility (2) describes receptive relaxation from vagus center, adaptive relaxation, and feedback relaxation mechanisms
Stomach motility (3) describes peristalsis, including grinding and mixing phases as well as regulated exit through the pyloric valve.
Stomach motility (4) relates to slow waves and action potentials in the regulation of gastric motility.
Stomach motility (5) involves intestinal-phase pathways inhibiting gastric emptying through CCK, secretin, GIP, and enterogastrones, reacting to duodenum stretch and chemoreceptors to pH, fats, and amino acids.

Vomiting

Vomiting is controlled by the vomiting center in the brain stem.
It's triggered by various neural inputs including extensive stomach distention, emetics, gagging, and motion sickness.
A series of muscle contractions forces stomach content through the esophagus and mouth.
Excessive vomiting can lead to dehydration.
Excess vomiting can disrupt electrolyte balance in the blood.
Aspiration risk and acid damage are potential complications.

Stomach Pathophysiology - Peptic Ulcers

Early 20th-century thinking attributed peptic ulcers to high stomach acidity.
Treatment mostly relied on antacids.
Ulcers often recurred despite treatment.
H. pylori bacteria is a major cause of peptic ulcers.
H. pylori bacteria produces urease, which breaks down urea into ammonia and CO2, neutralizes stomach acid, and disrupts the mucus layer
NSAIDs (pain relievers) also cause peptic ulcer through various mechanisms that can inhibit COX-1 and reduce prostaglandin E2 which can increase gastric acid.

Summary Points

Four major processes (motility, secretion, digestion, and absorption) are performed by the gastrointestinal tract
Histological structures accommodate specific digestive functions.
Neuronal and hormonal pathways regulate GI functions.
Upper GI tract includes saliva functions, salivary secretion regulation, and swallowing/vomiting processes.
The stomach contains different cell types in gastric epithelia (with their unique functions).
Mechanism of acid secretion regulation in stomach through gastrin.
The stomach's protective barrier against acidity and pepsin, along with the role and function of different cells for gastric production.
Pathophysiology is involved for H. pylori and NSAID-induced peptic ulcers.

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Description

This quiz covers the key concepts of gastrointestinal physiology, including the anatomy and functions of the GI tract, digestion, and absorption processes. Explore the intricate details of motility, secretion, and how various nutrients are processed within the body. Perfect for students looking to solidify their understanding of digestive physiology.