Gastrointestinal Tract Functions Quiz
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Questions and Answers

What is the primary function of the small intestine?

  • Digestion and absorption (correct)
  • Reabsorption of water and ions
  • Storage of processed food
  • Excretion of waste products

    • Which of the following is NOT a function of sphincters in the GI tract?

  • Isolating regions of the GI tract
  • Facilitating the movement of food along the GI tract (correct)
  • Preventing backflow of contents
  • Selective retention of contents

    • How does the GI tract contribute to excretion?

  • By absorbing waste products from the bloodstream
  • By converting waste products into usable nutrients
  • By storing and excreting waste substances from ingested food (correct)
  • By filtering out toxins from the bloodstream

    • What is the primary function of the colon?

    <p>Reabsorption of water and ions (A)</p> Signup and view all the answers

    Which of the following is NOT a substance excreted by the GI tract?

    <p>Carbohydrates (C)</p> Signup and view all the answers

    How is the liver's blood supply unique?

    <p>It receives a significant portion of its blood supply from the venous circulation (C)</p> Signup and view all the answers

    What is the primary reason for the dynamic regulation of GI blood flow?

    <p>To meet the metabolic needs of the gut wall and remove absorbed nutrients (A)</p> Signup and view all the answers

    Which of the following plexuses is NOT directly involved in controlling the contraction of the circular muscle?

    <p>Submucosal Plexus (C)</p> Signup and view all the answers

    What is the primary function of the submucosal plexus?

    <p>Secretion and absorption (B)</p> Signup and view all the answers

    Which of these plexuses are responsible for coordinating the coordinated movements of the gastrointestinal tract?

    <p>Myenteric Plexus (C)</p> Signup and view all the answers

    Which plexus is located between the circular and longitudinal muscle layers?

    <p>Myenteric Plexus (D)</p> Signup and view all the answers

    What is the role of the paravascular nerves in the gastrointestinal tract?

    <p>They regulate blood flow to the gastrointestinal tract. (D)</p> Signup and view all the answers

    What is the primary difference between the myenteric and submucosal plexuses?

    <p>The myenteric plexus controls muscle contraction while the submucosal plexus controls secretion. (D)</p> Signup and view all the answers

    Which of the following is NOT a function of the enteric nervous system?

    <p>Regulation of the autonomic nervous system (B)</p> Signup and view all the answers

    What is the significance of the term 'brain-gut peptides' in the context of the enteric nervous system?

    <p>These peptides act as chemical messengers within the enteric nervous system. (A)</p> Signup and view all the answers

    What is the function of the tertiary plexus in the gastrointestinal tract?

    <p>Coordination of the smooth muscle within the muscularis (C)</p> Signup and view all the answers

    Which of the following is a key characteristic of the enteric nervous system?

    <p>It is capable of independent function and can operate without input from the central nervous system. (C)</p> Signup and view all the answers

    What is the primary method of histamine diffusion in the postprandial period?

    <p>Across the interstitial space of the lamina propria (B)</p> Signup and view all the answers

    Which of the following statements accurately describes neuronal regulation of gastrointestinal (GI) function?

    <p>Neurotransmitters can affect cells even when there are no direct synapses between the nerve and the target cell. (C)</p> Signup and view all the answers

    What does the acronym 'PYY' stand for?

    <p>Peptide YY (D)</p> Signup and view all the answers

    What is the primary trigger for the release of Peptide YY (PYY)?

    <p>Fatty acids (A)</p> Signup and view all the answers

    What is the main function of posttranslational modifications in the context of peptide hormone receptors?

    <p>Confer receptor selectivity for specific peptide hormones (C)</p> Signup and view all the answers

    Which of the following accurately describes the mechanism of action of PYY?

    <p>PYY inhibits the release of digestive hormones like gastrin. (A)</p> Signup and view all the answers

    What is the main location for the release of PYY?

    <p>Ileum (D)</p> Signup and view all the answers

    Which of these is a possible mechanism for the regulation of GI function by PYY?

    <p>PYY acts on receptors in the brain to regulate hunger and appetite. (A)</p> Signup and view all the answers

    Which of these is NOT a characteristic of the regulatory peptide hormones released from endocrine cells of the gut?

    <p>They primarily act via paracrine mechanisms within the gut. (C)</p> Signup and view all the answers

    What are the three major control mechanisms in the gastrointestinal tract?

    <p>Hormonal, paracrine, and neurocrine (C)</p> Signup and view all the answers

    What type of innervation consists of cell bodies located outside the wall of the GI tract?

    <p>Extrinsic innervation (A)</p> Signup and view all the answers

    What physiological responses are mounted when nutrients are detected in different regions of the GI tract?

    <p>Endocrine, paracrine, and neurocrine pathways (B)</p> Signup and view all the answers

    Which of the following is NOT typically associated with extrinsic innervation?

    <p>Hormonal pathways originating from the GI wall (B)</p> Signup and view all the answers

    Which phase of the integrated response to a meal involves cognitive processes and anticipation of food consumption?

    <p>The cephalic phase (A)</p> Signup and view all the answers

    What is the peptide form that is more selective for the Y2 receptor?

    <p>PYY3-36 (C)</p> Signup and view all the answers

    Which enzyme is responsible for cleaving the peptide to PYY3-36?

    <p>Dipeptidyl peptidase IV (D)</p> Signup and view all the answers

    Which receptor is not involved in the binding of the original peptide?

    <p>Y3 (D)</p> Signup and view all the answers

    What triggers the release of GLP-1 from enteroendocrine cells in the gut wall?

    <p>Presence of luminal carbohydrate and lipids (C)</p> Signup and view all the answers

    GLP-1 is involved in the regulation of which physiological process?

    <p>Blood glucose level (D)</p> Signup and view all the answers

    In addition to insulin secretion, what else does GLP-1 stimulate?

    <p>Insulin biosynthesis (C)</p> Signup and view all the answers

    What is the role of serotonin (5-HT) in the gastrointestinal tract?

    <p>Stimulates acid production (D)</p> Signup and view all the answers

    Which of the following is the source of GLP-1?

    <p>Differential processing of glucagon gene (B)</p> Signup and view all the answers

    The presence of the enzyme that cleaves the peptide can alter what?

    <p>Biological response to PYY secretion (B)</p> Signup and view all the answers

    What type of cell releases GLP-1 in the gut?

    <p>Enteroendocrine cells (B)</p> Signup and view all the answers

    Flashcards

    GI Tract

    The gastrointestinal tract where digestion and absorption occur.

    Absorption

    The process of taking in nutrients from digested food.

    Chyme

    A thick semi-fluid mass of partially digested food.

    Colon's function

    The colon mainly absorbs water and ions from waste.

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    Sphincters

    Muscle structures that control flow in the GI tract.

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    Splanchnic blood flow

    Blood flow to the GI tract, receiving about 25% of cardiac output.

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    Liver and GI blood supply

    Liver receives blood from GI tract to process absorbed nutrients.

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    Control mechanisms

    The three major mechanisms regulating GI function: hormonal, paracrine, and neurocrine.

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    Extrinsic innervation

    Nerve signals originating from outside the GI tract, involving two subdivisions.

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    Intrinsic innervation

    Nerve signals that originate from within the wall of the GI tract.

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    Physiological responses

    Reactions initiated by sensory mechanisms detecting nutrients in various GI regions.

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    Three pathways of responses

    Responses to nutrient detection are mediated through endocrine, paracrine, and neurocrine pathways.

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    Histamine release

    Histamine is released during the postprandial period and diffuses in the interstitial space.

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    Neural regulation

    Neural regulation of GI function is crucial both locally within organs and between distant parts.

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    Neurotransmitter effect

    Neurotransmitters affect the cells they innervate, often without direct synapses.

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    Endocrine cells

    Endocrine cells in the gut wall release peptide hormones to regulate GI functions.

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    Receptor subtypes

    There are different receptor subtypes for regulatory peptide hormones like peptide YY (PYY).

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    Peptide YY (PYY)

    PYY is a hormone released in response to fatty acids, influencing digestive processes.

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    Posttranslational modifications

    Receptor selectivity for peptide hormones is determined by posttranslational modifications.

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    Lamina propria

    The lamina propria is a connective tissue layer in the gut where histamine can diffuse.

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    PYY

    A 36-amino acid peptide that binds to Y1, Y2, and Y5 receptors.

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    PYY3-36

    A cleaved form of PYY that is selective for the Y2 receptor.

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    Dipeptidyl peptidase IV

    An enzyme that cleaves peptides like PYY.

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    GLP-1

    A regulatory peptide released in response to carbohydrates and lipids.

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    Glucagon gene

    Genetic origin of GLP-1, expressed in pancreas and gut.

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    Insulin secretion

    Process stimulated by GLP-1 to manage blood glucose levels.

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    Enteroendocrine cells (EECs)

    Cells in the gut wall that release GLP-1.

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    Insulin sensitivity

    How effectively the body responds to insulin.

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    Serotonin (5-HT)

    A neurotransmitter that affects mood and is released by enteric cells.

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    Parietal cells

    Cells in the stomach that produce acid, stimulated by certain peptides.

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    Enteric Nervous System

    A complex network of neurons controlling gut function.

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    Myenteric Plexus

    A layer of the enteric nervous system located between muscle layers.

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    Submucosal Plexus

    Part of the enteric nervous system that manages secretions and blood flow.

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    Circular Muscle

    Muscle that encircles the GI tract; aids in peristalsis.

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    Longitudinal Muscle

    Muscle fibers running along the length of the GI tract.

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    Mucosal Plexus

    A part of the enteric nervous system located in the mucosa.

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    Gut Peptides

    Regulatory peptides involved in various digestive processes.

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    Teritary Plexus

    Emerges from the myenteric and submucosal plexi, integrating signals.

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    Perivascular Nerves

    Nerves located around blood vessels within the GI tract.

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    Reflex in GI Tract

    Automatic responses in the GI system triggered by stimuli.

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    Study Notes

    Section 6: Gastrointestinal Physiology

    • Kim E. Barrett and Helen E. Raybould authored the book
    • The book covers functional anatomy and general principles of regulation in Gastrointestinal Tract

    Chapter 27: Functional Anatomy and General Principles of Regulation in the Gastrointestinal Tract

    • The Gastrointestinal (GI) tract is comprised of the alimentary tract from the mouth to the anus, and also includes associated glands. Its function is to absorb nutrients and water, and eliminate waste products. Major processes are motility, secretion, digestion, and absorption.
    • The GI tract is exposed to external environment, thus it has a defense system against microorganisms.
    • The GI tract contains many functional segments: Mouth, pharynx, esophagus, stomach, duodenum, jejunum, ileum, colon, rectum, and anus. Associated with these are glands like Brunner's glands, which empty secretions into the lumen.
    • Other associated organs, such as salivary glands and pancreas, empty secretions into the gut lumen.

    Chapter 28: The Cephalic, Oral, and Esophageal Phases of the Integrated Response to a Meal

    • This chapter details the processes in the GI tract in the early stages of the integrated response to a meal.
    • The cephalic phase occurs before ingestion, driven by anticipation, smells, sights, sounds of food. This results in increased parasympathetic activity.
    • The oral phase is triggered when food is in the mouth. The responses in this phase (primarily salivary secretion), are identical to the cephalic phase.
    • The esophageal phase occurs when food moves from mouth to esophagus. This is mainly to prepare the GI tract for digestion and absorption, which involves swallowing.

    Chapter 29: The Gastric Phase of the Integrated Response to a Meal

    • This chapter details the processes in the GI tract when food is in the stomach.
    • The main function of the stomach is to act as a temporary reservoir for the meal and initiate protein digestion via acid and pepsinogen secretion.
    • The stomach is divided into the cardia, corpus, and antrum, with the latter two sections used in a proximal and distal functional sense.
    • The gastric mucosa is lined with gastric pits (the opening of ducts). These glands include regions like the isthmus, necks with mucous neck cells, and parietal cells, chief cells, and enterochromaffin-like (ECL) cells that secrete histamine and D cells that secrete somatostatin.
    • Stomach secretions protect the mucosa (mucus, HCO3), and initiate protein digestion. Components are acid (HCl), pepsinogen, mucus, intrinsic factor, and HCO3.
    • Gastric motility is regulated by endocrine (gastrin, somatostatin), paracrine, and neural pathways.

    Chapter 30: The Small Intestinal Phase of the Integrated Response to a Meal

    • This chapter covers digestion and absorption in the small intestine.
    • The small intestine plays a major role in assimilation due to its large surface area (folds, villi, microvilli)
    • Digestion occurs via many secretions:
      • Pancreatic juice: contains many proteolytic enzymes in their inactive forms. This is crucial for protein digestion, and these enzymes are activated at the appropriate time/site. Also contains bicarbonate to neutralize acid.
      • Bile: produced in the liver and stored in the gallbladder. It is a critical component for lipid digestion, providing detergents (bile acids) to increase lipid solubility.
    • The rates of gastric emptying are dependent on the type of meal consumed. Liquids empty more rapidly than solids.
    • Many factors regulate gastric emptying:
      • Distension
      • Nutrients.
      • Osmolarity
      • These result in changes in pancreatic secretion, gallbladder contraction, relaxation of sphincters of Oddi, regulation of gastric emptying, and inhibition of gastric acid secretion.

    Chapter 31: The Colonic Phase of the Integrated Response to a Meal

    • The large intestine is the most distal part of the Gastrointestinal tract and includes the cecum, the ascending, transverse, descending portions of the colon, rectum and anus
    • Its primary roles include digestion/absorption of unabsorbed nutrients; reabsorption of water and electrolytes; storage of waste; and the microbiome.
    • Motility of the large intestine is largely designed for mixing and retention, rather than propulsion. Thus, its most distinctive feature is the production of haustra (sacculations or pockets).
    • The large intestine also stores and releases indigestible materials.
    • Key neural/hormonal signals and feedback loops regulate colonic function.
    • The microbiota in the colon interact with substances in the intestinal tract and play a major role in metabolism and host defense.

    Chapter 32: Transport and Metabolic Functions of the Liver

    • The liver is a major metabolic center, involved in carbohydrate, lipid, and protein metabolism.
    • The liver plays a crucial role in detoxification of various substances.
    • The liver contains specialized cell types that form cords around sinusoids, allowing efficient exchange of blood and metabolites.
    • Bile is a key product of liver function, involved in lipid digestion and excretion.
    • Ammonia is processed into urea in the liver and excreted in the urine.
    • The liver is a crucial processing point for many substances (drugs, nutrients, and wastes) before they enter circulation or are excreted.

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