Gastrointestinal Tract Functions
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Questions and Answers

Which substances stimulate acid secretion in the stomach?

  • Sympathetic stimulation
  • Vagus nerve (correct)
  • Histamine (correct)
  • Cholecystokinin
  • Which phase of acid secretion occurs during eating?

  • Intestinal phase
  • Mucosal phase
  • Gastric phase (correct)
  • Cephalic phase
  • What role does bile play in digestion?

  • Inhibits digestive enzymes
  • Absorbs carbohydrates
  • Emulsifies fats (correct)
  • Digests proteins
  • What vessel primarily supplies blood to the small intestine?

    <p>Superior mesenteric artery (A)</p> Signup and view all the answers

    Where in the intestinal tract does the absorption of vitamin B12 primarily occur?

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

    What is the function of the sphincter of Oddi?

    <p>Controls the flow of bile and pancreatic enzymes (C)</p> Signup and view all the answers

    Which of the following is NOT a function of the small intestine?

    <p>Secretion of bilirubin (A)</p> Signup and view all the answers

    Which structure prevents backflow from the large intestine to the small intestine?

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

    What are the primary functions of the gastrointestinal tract?

    <p>Mechanical and chemical breakdown of food along with nutrient absorption (C)</p> Signup and view all the answers

    Which layer is NOT part of the gastrointestinal tract walls?

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

    What is the role of the lower esophageal sphincter?

    <p>To prevent regurgitation of food into the esophagus (B)</p> Signup and view all the answers

    Where does digestion first begin in the gastrointestinal tract?

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

    What type of muscle is found in the upper part of the esophagus?

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

    Which hormone is involved in delaying gastric emptying?

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

    What substance do chief cells in the stomach secrete?

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

    Which of the following is NOT a part of the nerve control of the gastrointestinal tract functions?

    <p>Cranial nerve III (C)</p> Signup and view all the answers

    What role does cholecystokinin play in the digestive process?

    <p>It triggers gallbladder contraction to release bile. (A)</p> Signup and view all the answers

    What enzymes does the exocrine pancreas secrete for digestion?

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

    Which of the following is a significant indicator of pancreatic dysfunction?

    <p>Increased serum amylase levels (D)</p> Signup and view all the answers

    How does aging affect the gastrointestinal system?

    <p>It can lead to reduced appetite due to altered taste and smell. (A)</p> Signup and view all the answers

    What stimulates the pancreas to secrete alkaline fluid?

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

    What diagnostic tests are used to evaluate liver function?

    <p>Blood studies for LDH, AST, and ALT (D)</p> Signup and view all the answers

    What effect does aging have on gastric digestions and emptying?

    <p>It slows gastric digestion and emptying. (A)</p> Signup and view all the answers

    Which test would likely indicate an obstructive disease of the gallbladder?

    <p>Elevated serum bilirubin levels (A)</p> Signup and view all the answers

    What is the primary function of the hepatic portal vein?

    <p>To ferry nutrient-rich blood from the intestines to the liver (B)</p> Signup and view all the answers

    Which process describes the recycling of bile acids and salts back to the liver?

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

    Which statement about bilirubin is correct?

    <p>Unconjugated bilirubin can cross cell membranes due to being fat-soluble. (A)</p> Signup and view all the answers

    What substance is synthesized by hepatocytes from cholesterol?

    <p>Primary bile acids (C)</p> Signup and view all the answers

    Which of the following proteins is NOT synthesized by the liver?

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

    What are the major components of fat synthesized by the liver?

    <p>Glycerol and fatty acids (B)</p> Signup and view all the answers

    What role do Kupffer cells play in the liver?

    <p>They destroy microorganisms in the blood. (C)</p> Signup and view all the answers

    What is the primary storage form of glucose in the liver?

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

    What role do the villi play in fat absorption in the intestines?

    <p>They facilitate the diffusion of fat into lacteals. (C)</p> Signup and view all the answers

    Which type of reflex is triggered by distention of the ileum?

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

    What are haustra in the context of the large intestine?

    <p>Pouches created by circular muscle contractions. (A)</p> Signup and view all the answers

    Which part of the large intestine does NOT include haustra?

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

    What occurs during defecation?

    <p>Rectal distention stimulates relaxation of internal anal sphincter. (D)</p> Signup and view all the answers

    Which statement accurately describes the liver's functions?

    <p>The liver functions in digestion, metabolism, and immunology. (B)</p> Signup and view all the answers

    What triggers the intestinointestinal reflex?

    <p>Overdistention of one intestinal segment (A)</p> Signup and view all the answers

    Which of the following correctly describes the composition of the intestinal bacteria in the colon?

    <p>They are predominantly consisting of Bacteroides and clostridia. (A)</p> Signup and view all the answers

    Flashcards

    Peristalsis

    The process involving sequential relaxations and contractions of muscles, moving food through the gastrointestinal tract.

    Lower Esophageal Sphincter

    The lower esophageal sphincter's function is to prevent food from going back up into the esophagus.

    Stomach

    A bag-like structure that mixes and stores food, secretes digestive juices, and propels partially digested food into the duodenum.

    Vagus Nerve and Gastric Function

    The vagus nerve stimulates gastric secretions and motility.

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    Hormonal Control of Gastric Emptying

    Gastrin and motilin are hormones that stimulate the stomach's emptying, while secretin and cholecystokinin slow down the process.

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    Chief Cells and Pepsinogen

    Chief cells secrete pepsinogen, which is converted to pepsin in the acidic environment created by hydrochloric acid.

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    Gastric Glands

    These glands secrete intrinsic factor, which is needed for vitamin B12 absorption, and hydrochloric acid, which dissolves food fibers, kills microorganisms, and activates the enzyme pepsin.

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    Digestion in the Mouth

    The process of chewing and salivation, where α-amylase in saliva initiates carbohydrate digestion.

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    Segmentation

    The process by which chyme (partially digested food) is mixed and propelled along the intestinal tract by alternating contractions of circular and longitudinal muscles.

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    Ileogastric Reflex

    The inhibitory reflex triggered when the ileum is distended, slowing down gastric emptying.

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    Intestinointestinal Reflex

    The reflex that inhibits intestinal motility when one segment is overdistended, preventing overstretching.

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    Gastroileal Reflex

    The reflex that increases intestinal motility when gastric motility increases, preparing for the incoming food.

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    Gastrocolic Reflex

    The reflex triggered by distention of the ileum with chyme, causing a mass movement of feces towards the rectum.

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    Defecation

    The process of expelling feces from the rectum, triggered by rectal distension.

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    Liver

    The largest organ in the body, responsible for various functions, including digestion, metabolism, and detoxification.

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    Three phases of acid secretion

    The cephalic phase is triggered by the anticipation of food, taste, or smell, while the gastric phase is initiated by the presence of food in the stomach, and the intestinal phase is activated by the arrival of chyme in the small intestine.

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    Duodenum's role in digestion

    The duodenum receives chyme from the stomach and triggers the liver to release bile and the pancreas to secrete enzymes and alkaline fluids.

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    Villi in the small intestine

    These projections increase the surface area of the small intestine, aiding in the absorption of nutrients.

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    Role of the small intestine

    The small intestine is the primary site for digestion and absorption of ingested nutrients and water.

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    Enzymes involved in small intestine digestion

    These enzymes aid in the breakdown of carbohydrates, proteins, and fats within the small intestine.

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    The Peritoneum

    The peritoneum, a double-layered membrane, surrounds the abdominal organs, providing support and protection.

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    Superior mesenteric artery

    The superior mesenteric artery supplies primary blood flow to the small intestine, ensuring nutrient delivery and waste removal.

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    Bile's role in digestion

    Bile, produced by the liver, aids in the digestion and absorption of fats. It also neutralizes acidic chyme, facilitating protein, carbohydrate, and sugar digestion by pancreatic enzymes.

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    Primary vs. Secondary Bile Acids

    The primary bile acids, synthesized from cholesterol by the hepatocytes, are conjugated to form bile salts. Secondary bile acids are formed from bile salt deconjugation by bacteria in the intestinal lumen.

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    Enterohepatic Circulation

    Bile salts and acids are absorbed from the terminal ileum and returned to the liver.

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    Bilirubin Metabolism

    Bilirubin, a breakdown product of aged red blood cells, is made water-soluble by hepatocytes and excreted in bile.

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    Liver's Role in Fat Metabolism

    The liver makes fats from protein and carbohydrates (glycerol, fatty acids, phospholipids, and cholesterol) and converts dietary triglycerides into glycerol and fatty acids.

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    Liver's Role in Protein Metabolism

    The liver requires essential amino acids to make albumin, globulin, serum enzymes, and can convert amino acids to carbohydrates by removing ammonia.

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    Liver's Role in Carbohydrate Metabolism

    The liver can release glucose, store carbohydrates as glycogen, or convert carbohydrates to fat.

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    Liver Detoxification

    The liver detoxifies substances from the body, including harmful chemicals, drugs, and waste products.

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    Gallbladder Function

    The gallbladder, located beneath the liver, stores bile between meals and releases it when chyme triggers the release of cholecystokinin.

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    Bile Release

    Bile is released from the gallbladder through the cystic duct and common bile duct into the duodenum to help digest fats.

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    Pancreatic Enzymes

    The pancreas produces enzymes such as trypsin, chymotrypsin, and lipase that break down proteins, carbohydrates, and fats, respectively.

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    Secretin's Role

    The hormone secretin stimulates the pancreas to release alkaline fluid, which neutralizes the acidic chyme coming from the stomach.

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    Cholecystokinin and ACh

    Cholecystokinin and acetylcholine stimulate the pancreas to release digestive enzymes, specifically trypsin, chymotrypsin, and lipase.

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    Pancreas' Endocrine Function

    The pancreas produces insulin and glucagon, which regulate blood sugar levels.

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    Elevated Serum Amylase

    Elevated levels of serum amylase indicate pancreatic dysfunction, as this enzyme is vital for carbohydrate digestion.

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    Aging and Digestion

    Aging can lead to diminished senses of taste and smell, reduced salivary secretions, and decreased gastric motility.

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    Aging and Intestines

    Decreased intestinal motility and absorption of nutrients can occur with age, potentially leading to nutritional deficiencies.

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    Study Notes

    Gastrointestinal Tract Functions

    • The gastrointestinal tract breaks down food mechanically and chemically, absorbing digested nutrients.
    • It's a hollow tube from mouth to anus.
    • Layers include mucosa, muscularis mucosa, submucosa, muscularis, and serosa (or adventitia).
    • Functions (besides swallowing and defecation) are controlled by autonomic nerves (vagus, sympathetic, splanchnic) and intrinsic enteric nerves and hormones.

    Digestion Begins in the Mouth

    • Digestion starts with chewing and saliva containing amylase, which digests carbohydrates.

    Esophagus

    • Transports food from mouth to stomach.
    • Upper part has striated muscle; lower part has smooth muscle.
    • Controlled by a swallowing center in the brainstem.

    Two Phases of Swallowing

    • Oropharyngeal (voluntary)
    • Esophageal (involuntary)

    Food Propulsion

    • Peristalsis: sequential muscular contractions move food through the tract.
    • Lower esophageal sphincter controls movement into the stomach, preventing regurgitation.

    Stomach

    • Bag-like structure storing and mixing food, producing digestive juices.
    • Smooth muscle layers (longitudinal, circular, oblique) mix and propel food.
    • Vagus nerve stimulates gastric secretion and motility, while gastrin and motilin stimulate emptying; secretin and cholecystokinin slow emptying.
    • Gastric glands produce intrinsic factor (for vitamin B12 absorption) and hydrochloric acid (dissolving fibers, killing microbes, activating pepsin).
    • Chief cells secrete pepsinogen, converted to pepsin by acid.
    • Acid secretion is stimulated by vagus nerve, gastrin, histamine, and inhibited by sympathetic stimulation and cholecystokinin. Acetylcholine stimulates pepsin secretion.

    Small Intestine

    • 5 meters long, with three sections: duodenum, jejunum, and ileum.
    • Digestion and absorption of most nutrients and water occur here.
    • Bile from liver and enzymes from pancreas aid digestion.
    • Bile is produced by the liver, essential for fat digestion and absorption, and has alkaline properties to neutralize chyme for optimal enzyme action.
    • Enzymes (maltase, sucrase, lactase, proteases, amylase, lipase) digest various food groups.
    • Digested products are absorbed into the blood via the hepatic portal vein for further processing.
    • Villi increase surface area for absorption.

    Large Intestine

    • Three bands of longitudinal muscle (teniae coli) form pouches (haustra), aiding in mass movements of feces.
    • Absorbs water and electrolytes.
    • Stores and eliminates feces.

    Accessory Digestive Organs

    • Liver: Largest organ, involved in digestion, metabolism, blood composition, and immune functions.
      • Produces bile to aid fat digestion, stored in the gallbladder.
      • Hepatocytes are the functional cells of the liver; they produce bile, process blood, and synthesise various substances in the body.
    • Gallbladder: Stores and concentrates bile.
    • Pancreas: Endocrine and exocrine functions
      • Endocrine: produces hormones (insulin and glucagon) regulating blood sugar.
      • Exocrine: secretes enzymes and alkaline fluid assisting in digestion of food.

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    Description

    This quiz explores the functions and structure of the gastrointestinal tract, including the processes of digestion from the mouth to the esophagus. It covers the mechanics of food propulsion and the roles of various muscles and nerves involved in swallowing. Assess your understanding of how food is processed in the body.

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