Digestive System Anatomy and Physiology
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Questions and Answers

Which of the following hormones promotes appetite?

  • Leptin
  • Ghrelin (correct)
  • Insulin
  • Alpha Melanocyte Stimulating Hormone (a-MSH)

    • Which of the following hormones is produced by the pancreas?

  • Peptide YY
  • Amylin (correct)
  • Ghrelin
  • Leptin

    • Which of the following hormones is primarily involved in regulating blood glucose levels?

  • Ghrelin
  • Insulin (correct)
  • Leptin
  • Amylin

    • Which of the following best describes the relationship between leptin and obesity?

    <p>Leptin insensitivity can contribute to obesity. (B)</p> Signup and view all the answers

    Which of the following neurons in the arcuate nucleus are stimulated by ghrelin?

    <p>Neuropeptide Y (NPY) secreting neurons (D)</p> Signup and view all the answers

    What type of teeth are primarily responsible for shredding food?

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

    How many teeth do adults typically have?

    <p>32 (D)</p> Signup and view all the answers

    What is the outer covering of the crown of a tooth called?

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

    Which component in saliva is responsible for starting starch digestion?

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

    Which cells secrete gastric acid in the stomach?

    <p>Parietal cells (A)</p> Signup and view all the answers

    What does the pyloric sphincter connect?

    <p>Stomach and small intestine (B)</p> Signup and view all the answers

    What protects the stomach lining from its acidic environment?

    <p>Mucous bicarbonate barrier (D)</p> Signup and view all the answers

    Which cells in the gastric glands secrete histamine?

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

    Which of the following cells in the intestine are responsible for producing mucus?

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

    What is the main role of enteroendocrine cells in the intestine?

    <p>Secrete hormones like secretin and CCK (D)</p> Signup and view all the answers

    Which process occurs after glycolysis in glucose oxidation?

    <p>Pyruvate processing (B)</p> Signup and view all the answers

    During fat digestion in the small intestine, what role do bile salts play?

    <p>Facilitate micelle formation (B)</p> Signup and view all the answers

    What are the products of the Krebs cycle?

    <p>Water and carbon dioxide (D)</p> Signup and view all the answers

    How are lipids transported across the intestinal epithelium?

    <p>Through micelles that diffuse into the cell (D)</p> Signup and view all the answers

    Which enzyme is involved in breaking down disaccharides into monosaccharides?

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

    What is the main function of stem cells in the intestine?

    <p>Renew intestinal cells (D)</p> Signup and view all the answers

    What are the major organs of the digestive tract?

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

    Which layer of the digestive tract is responsible for housing the submucosal plexus?

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

    What is the primary role of the myenteric plexus?

    <p>Controlling gastrointestinal motility (B)</p> Signup and view all the answers

    What distinguishes long reflexes from short reflexes in digestion?

    <p>Long reflexes involve stimuli outside the ENS (C)</p> Signup and view all the answers

    Where does peristalsis primarily occur in the digestive tract?

    <p>Esophagus and stomach (A)</p> Signup and view all the answers

    What is the role of segmentation in digestion?

    <p>Mixing materials without net movement (B)</p> Signup and view all the answers

    Which physiological step of digestion involves the elimination of feces?

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

    Which of the following is NOT an accessory organ of the digestive tract?

    <p>Small Intestine (A)</p> Signup and view all the answers

    What is the primary function of chylomicrons in the body?

    <p>Carry triglycerides from the small intestine to body cells (A)</p> Signup and view all the answers

    Which lipoprotein is mainly composed of cholesterol?

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

    What is the main purpose of lipogenesis?

    <p>Store excess carbohydrates and amino acids as triglycerides (A)</p> Signup and view all the answers

    What sequence describes the transformation of VLDL as it loses triglycerides?

    <p>VLDL -&gt; IDL -&gt; LDL (B)</p> Signup and view all the answers

    What is lipolysis?

    <p>The breakdown of fats into fatty acids and glycerol (D)</p> Signup and view all the answers

    How do HDL lipoproteins function in the body?

    <p>They transport excess cholesterol back to the liver (A)</p> Signup and view all the answers

    What happens to excess acetyl CoA generated from a high carbohydrate diet?

    <p>It is converted to fatty acids (A)</p> Signup and view all the answers

    Which of the following is an effect of lipolysis?

    <p>Increased supply of fatty acids for energy (A)</p> Signup and view all the answers

    What neural factor stimulates HCl production in the gastric lumen?

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

    Which phase of gastric acid secretion accounts for the highest percentage?

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

    What role does histamine play in gastric acid secretion?

    <p>Instructs parietal cells to make HCl (A)</p> Signup and view all the answers

    Which part of the small intestine is primarily responsible for the neutralization of acidic chyme?

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

    How does the intestinal phase affect gastric acid secretion?

    <p>Inhibits gastric secretion and motility (D)</p> Signup and view all the answers

    What is the main function of the jejunum in the small intestine?

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

    Which hormone is secreted by the S cells in the duodenum to inhibit gastric secretion?

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

    Where does the small intestine end?

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

    Study Notes

    Digestive Tract Organs

    • Major organs: oral cavity, pharynx, esophagus, stomach, small intestine, large intestine
    • Accessory organs: teeth, tongue, salivary glands, liver, gallbladder, pancreas

    Alimentary Canal

    • Path food takes from mouth to anus
    • Includes stomach and intestines (short and long)

    Digestive Tract Layers

    • Four layers (central to outer): mucosa, submucosa, muscularis propria, adventitia/serosa
    • Submucosa houses submucosal plexus
    • Muscularis propria has circular and longitudinal smooth muscle; myenteric plexus in circular muscle.

    Reflexes in Digestion

    • Long reflexes: involve CNS and ANS, outside the ENS.
    • Short reflexes: involve ENS, respond to stimuli in the digestive tract.

    Peristalsis

    • Waves of contraction by smooth muscles in the digestive tract to propel materials.
    • Occurs in esophagus, stomach, and intestines.

    Segmentation

    • Back and forth contraction/relaxation to mix undigested materials with intestinal secretions.
    • No net movement.
    • Occurs in intestines.

    Major Physiological Steps

    • Ingestion: intake of food

    Digestive Enzymes

    • Amylase: starts starch digestion (stimulated by CCK)
    • Lipase: begins fat digestion

    Stomach Regions

    • Cardia, fundus, body, and pyloric part

    Stomach Protection

    • Mucous bicarbonate barrier: bicarbonate neutralizes acid
    • Epithelial tight junctions: prevent gastric juice from seeping
    • Replacement of epithelial cells (every 3-6 days)

    Stomach Cells and Secretions

    • Mucous neck cells: secrete mucus and bicarbonate.

    • Parietal cells: secrete gastric acid (HCl) and intrinsic factor

    • Chief cells: secrete pepsinogen (activated to pepsin by HCl), and gastric lipase

    • G cells: secrete gastrin to increase acid secretion

    • Enterochromaffin cells: secrete histamine

    Gastric Juice Composition

    • Primarily water, acid, and pepsin.

    HCl Secretion Mechanism

    • Hydrogen and chloride ions produced separately within the cytosol.
    • Bicarbonate and H+ ions are involved.
    • Cl- moves easily into gastric lumen.
    • H+ moves in by K+ exchange.

    Stimuli for HCl Production

    • Neural: acetylcholine from parasympathetic nerve fibers
    • Hormonal: gastrin from G cells in duodenum and pyloric antrum
    • Paracrine: histamine from ECL cells

    Gastric Acid Secretion Phases

    • Cephalic phase (20%): triggered by smell, taste, and thought of food.
    • Gastric phase (50-60%): begins with food entering the stomach.
    • Intestinal phase (5-10%): begins as chyme enters duodenum

    Small Intestine Sections

    • Duodenum: neutralizes acidic chyme; receives chyme, pancreatic juice, bile.
    • Jejunum: digestion and absorption
    • Ileum: absorption of vitamin B12 & bile salts

    Small Intestine Cells

    • Enterocytes: nutrient digestion and absorption
    • Goblet cells: produce mucus
    • Paneth cells: secrete antimicrobial peptides
    • Stem cells: intestinal renewal
    • Enteroendocrine cells: secrete hormones (e.g., secretin, CCK)

    Small Intestine Functions

    • Absorb vitamins (produced by bacteria)
    • Absorb water
    • Compact feces

    Amylase and Brush Border Enzymes

    • Amylase: secreted by acinar pancreatic cells stimulated by CCK
    • Brush border enzymes:
      • Dextrinase & glucoamylase (breaks down >3 sugars)
      • Disaccharidases (breaks down 2 sugars)
      • Sucrase, maltase, lactase

    Glucose Oxidation Summary

    • Glycolysis: glucose to 2 pyruvates, producing NADH
    • Pyruvate processing: pyruvate to acetyl CoA, producing NADH
    • Krebs cycle: acetyl CoA oxidized to CO2, producing NADH and FADH2
    • Electron transport & oxidative phosphorylation: ATP production

    Bile Composition

    • 95% water, 5% solutes (bile acids, salts, phospholipids, cholesterol)

    Bile Digestion and Transport of Fats

    • Emulsification: break down large fat globules into smaller droplets
    • Bile salts combine to form micelles to incorporate lipids.
    • Micelles diffuse into intestinal cells, convert back to triglycerides, and form chylomicrons
    • Chylomicrons enter lacteals, then lymphatic system, and finally bloodstream.

    Lipoproteins

    • Small droplets with cholesterol/triglycerides in core, proteins/phospholipids in coating.
    • Density varies based on lipid vs. protein content.

    Lipid Transport Summary

    • Chylomicrons carry triglycerides from small intestine to body cells.
    • Bloodstream - liver.
    • Chylomicron remnants go to the liver.
    • LDL (lower protein): delivers cholesterol
    • HDL(higher protein): picks up cholesterol for removal.

    Short-Term Appetite Regulators

    • Ghrelin (hunger): secreted when stomach is empty.
    • Amylin, CCK, and Peptide YY (satiety): secreted when food is consumed.

    Long-Term Appetite Regulators

    • Leptin: indicates current energy stores, secreted by fat tissue.
    • Insulin: regulates blood glucose; effects appetite.

    Arcuate Nucleus Role

    • Receives signals from hunger and satiety chemicals (e.g., ghrelin, leptin).
    • Acts on orexigenic (NPY) or anorexigenic (melanocortin) neurons.

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    Exam 1 Digestive System, BIOL 20400

    Description

    Explore the major and accessory organs of the digestive tract, including the layers of the alimentary canal and the processes of peristalsis and segmentation. This quiz covers the intricate functions of the digestive system and how reflexes play a role in digestion.

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