MBBS Year 1 Gastrointestinal Physiology Lectures
40 Questions
5 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary propulsion force that drives food through the GI tract?

  • Voluntary muscle movement
  • Gravity
  • Involuntary muscular contraction (correct)
  • Involuntary nervous stimulation

    • What is the primary function of the submucosa layer in the GI tract?

  • Absorption of nutrients
  • Support and structure for the mucosa (correct)
  • Secretion of digestive enzymes
  • Muscular contraction and relaxation

    • What is the primary site of nutrient absorption in the GI tract?

  • Liver
  • Stomach
  • Mouth
  • Intestine (correct)

    • What is the function of hormones released by endocrine cells in the GI epithelium?

    <p>Regulation of digestion and absorption</p> Signup and view all the answers

    What is the function of salivary and gastrointestinal fluid secretions in the GI tract?

    <p>To provide optimal pH and ionic composition for digestion</p> Signup and view all the answers

    What is the function of the enterohepatic circulation in the GI tract?

    <p>Regulation of bile secretion</p> Signup and view all the answers

    What is the primary site of initial digestion of food in the GI tract?

    <p>Mouth and stomach</p> Signup and view all the answers

    What is the fate of salivary and gastrointestinal fluid secretions in the GI tract?

    <p>They are largely reabsorbed</p> Signup and view all the answers

    What is the primary function of the smooth muscles in the muscularis mucosae?

    <p>To create folds and ridges in the mucosa</p> Signup and view all the answers

    Which of the following is NOT part of the four concentric layers of the gastrointestinal tract?

    <p>Subserosa</p> Signup and view all the answers

    What is the role of Messner's plexus in the digestive tract?

    <p>Sending nerve fibers to the mucosa and muscularis layers</p> Signup and view all the answers

    Which secretion from the liver assists with digestion in the small intestine?

    <p>Bile salts</p> Signup and view all the answers

    In which part of the digestive tract does the majority of carbohydrate and amino acid absorption take place?

    <p>Small intestine</p> Signup and view all the answers

    What distinguishes the upper esophagus and anal sphincter from other parts of the muscularis externa?

    <p>Striated muscle fibers</p> Signup and view all the answers

    What type of connective tissue is primarily found in the lamina propria of the mucosa?

    <p>Vascularized loose connective tissue</p> Signup and view all the answers

    What is the main purpose of the muscular valves or sphincters in the gastrointestinal tract?

    <p>To separate different digestive organs</p> Signup and view all the answers

    What is the primary role of parietal cells in the gastric gland?

    <p>Secretion of hydrochloric acid</p> Signup and view all the answers

    What stimulates the secretion of histamine from enterochromaffin-like cells?

    <p>Action of gastrin on CCK2 receptors</p> Signup and view all the answers

    Which hormone is released by G cells and plays a role in stimulating parietal cells?

    <p>Gastrin</p> Signup and view all the answers

    How does PGE2 affect gastric acid secretion?

    <p>It inhibits the action of histamine</p> Signup and view all the answers

    What is the primary function of chief cells in the gastric gland?

    <p>Synthesis and secretion of pepsinogen</p> Signup and view all the answers

    What is a key structural feature of parietal cells that aids in their function?

    <p>Specialized intracellular canaliculi</p> Signup and view all the answers

    What mediates the potentiation of acid secretion by parietal cells?

    <p>Simultaneous binding of two of three specific agonists</p> Signup and view all the answers

    What is the diameter of parietal cells in the gastric gland?

    <p>25 µM</p> Signup and view all the answers

    Which mechanism primarily contributes to the secretion of gastric acid in Zollinger-Ellison Syndrome?

    <p>Stimulation of ECL cells by histamine</p> Signup and view all the answers

    What is the typical pH range observed in the jejunum of patients with Zollinger-Ellison Syndrome?

    <p>1.0 to 3.6</p> Signup and view all the answers

    Which cellular component predominates in the exocrine function of the pancreas?

    <p>Acinar cells</p> Signup and view all the answers

    What role does pepsinogen play in the pathophysiology of Zollinger-Ellison Syndrome?

    <p>It converts to pepsin in low pH environments</p> Signup and view all the answers

    Which part of the pancreas is predominantly drained by the main pancreatic duct?

    <p>All parts equally</p> Signup and view all the answers

    What is the primary factor leading to diarrhea in patients with Zollinger-Ellison Syndrome?

    <p>Elevated gastric acid levels</p> Signup and view all the answers

    Which characteristic is true of the pancreas's endocrine tissue?

    <p>It accounts for approximately 2-4% of pancreatic mass</p> Signup and view all the answers

    What type of nervous system innervation primarily influences pancreatic secretion?

    <p>Both sympathetic and parasympathetic nervous systems</p> Signup and view all the answers

    What effect does atropine have on saliva and blood flow?

    <p>It blocks saliva secretion but does not block blood flow.</p> Signup and view all the answers

    What is the primary mechanism that leads to increased salivary secretion?

    <p>Reflex response controlled by parasympathetic and sympathetic nerves.</p> Signup and view all the answers

    Which electrolytes are involved in the modification of primary saliva in the striated duct system?

    <p>Na+ and Cl- are reabsorbed while K+ and HCO3- are secreted.</p> Signup and view all the answers

    What role does the Na+-K+-2Cl- co-transporter play in salivary secretion?

    <p>It facilitates the reuptake of Cl- into acinar cells.</p> Signup and view all the answers

    What happens to Cl- conductance when the stimulation of salivary secretion stops?

    <p>It increases to restore KCl concentrations.</p> Signup and view all the answers

    What initiates the release of neurotransmitters and hormones in the salivary secretion mechanism?

    <p>Elevated intracellular Ca2+ following stimulation.</p> Signup and view all the answers

    In the context of salivary secretion, what is the significance of K+ channels on the basolateral membrane?

    <p>They assist in the activation of Cl- channels in the luminal membrane.</p> Signup and view all the answers

    Which of the following stimuli does NOT contribute to salivary secretion?

    <p>Low blood pressure in the salivary glands.</p> Signup and view all the answers

    Study Notes

    Overview of the Digestive System

    • The gastrointestinal (GI) tract comprises four main layers: serosa, muscularis externa, submucosa, and mucosa.
    • Functions of GI tract layers include protection, absorption, and motility regulation.

    Functions of Salivary, Gastric, and Pancreatic Secretions

    • Salivary secretions start digestion with enzymes like amylase that break down carbohydrates.
    • Gastric secretions, including HCl from parietal cells, facilitate protein digestion and create an acidic environment for pepsin activation.
    • Pancreatic secretions, rich in digestive enzymes, enter the small intestine, where they further aid in nutrient breakdown.

    Regulation of Digestion and Absorption

    • Digestion begins in the mouth and continues in the stomach; primary absorption of nutrients occurs in the small intestine.
    • Endocrine cells in the GI epithelium, like G cells, release hormones (e.g., gastrin) to modulate digestive activity.

    Mechanisms of Bile Secretion and Enterohepatic Circulation

    • Bile secretion is regulated by hormonal signals from the intestine, primarily cholecystokinin (CCK).
    • Enterohepatic circulation involves the recycling of bile acids from the intestine back to the liver.

    Histological Organization of the GI Tract

    • The GI tract, from esophagus to large intestine, consists of four concentric layers: mucosa, submucosa, muscularis externa, and serosa/adventitia.
    • Mucosa includes epithelium, lamina propria (connective tissue), and muscularis mucosae, enabling absorption and secretion.
    • Submucosa contains blood vessels, lymphatics, and neural plexus (Meissner's plexus) for regulation of the GI tract's functions.

    Salivary Secretory Mechanisms

    • Saliva formation occurs in a two-step process starting with isotonic primary fluid produced by acinar cells, modified in the ducts.
    • Salivary secretion is stimulated by sensory input like taste or smell, regulated by both parasympathetic and sympathetic nerves.

    Gastric Acid Secretion Regulation

    • HCl secretion in the stomach is mediated by gastrin, histamine, and acetylcholine acting on parietal cells.
    • Histamine from enterochromaffin-like cells plays a central role in stimulating gastric acid secretion.
    • Prostaglandin E2 (PGE2) inhibits gastric acid secretion by blocking histamine's action.

    Zollinger-Ellison Syndrome (ZES)

    • ZES is characterized by gastrin-secreting tumors (gastrinomas) in the pancreas or duodenum, leading to excessive gastric acid production.
    • Symptoms include peptic ulcers and diarrhea due to increased gastric acidity and pepsinogen conversion to active pepsin.

    Regulation of Pancreatic Secretion

    • The pancreas, approximately 90-100 g in weight, serves as a mixed endocrine and exocrine gland, primarily composed of acinar cells.
    • The main pancreatic duct drains digestive secretions into the duodenum, where they participate in nutrient digestion.
    • Pancreatic acini contain zymogen granules filled with digestive enzymes, responsible for significant digestive activity in the small intestine.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    MBBS Year 1 GI Lecture Notes - Prof GE Mann PDF

    Description

    Summary notes for Prof GE Mann's GI Lectures 1-5, covering key concepts and information from narrated powerpoint lectures.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser