Digestive System Functions Overview
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Questions and Answers

What is the main function of the outer longitudinal layers of muscle in the digestive tract?

  • Absorption of nutrients
  • Secretion of digestive enzymes
  • Synthesis of plasma proteins
  • Mechanical processing and moving materials (correct)
  • Which structure covers the muscularis externa in most portions of the digestive tract?

  • Mucosa
  • Submucosa
  • Adventitia
  • Serosa (correct)
  • What major digestive function occurs in the oral cavity?

  • Carbohydrate synthesis
  • Mechanical digestion (correct)
  • Lipid absorption
  • Nutrient absorption
  • Which organ processes blood leaving the absorptive surfaces of the digestive tract?

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

    What general category does the function of converting ammonia to urea fall under in the liver?

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

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

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

    What initiates carbohydrate digestion in the oral cavity?

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

    Which vitamin is absorbed and broken down by the liver?

    <p>Vitamin B12 (C)</p> Signup and view all the answers

    What is the function of bicarbonate secreted by the pancreas in the small intestine?

    <p>To neutralize stomach acid (A)</p> Signup and view all the answers

    Which segment of the small intestine is primarily responsible for the most nutrient absorption?

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

    What distinguishes the colon from the small intestine?

    <p>It forms pouches called haustra (C)</p> Signup and view all the answers

    What is the primary role of bile salts in digestion?

    <p>To emulsify lipid droplets for increased enzyme accessibility. (D)</p> Signup and view all the answers

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

    <p>Producing enzymes for digestion (D)</p> Signup and view all the answers

    What happens to bile while it is stored in the gall bladder?

    <p>It becomes more concentrated as water is absorbed. (D)</p> Signup and view all the answers

    Where does the small intestine begin and end?

    <p>Pyloric sphincter to cecum (B)</p> Signup and view all the answers

    Which cells in the stomach secrete hydrochloric acid?

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

    Which part of the large intestine serves as the first section that receives chyme from the ileum?

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

    What is the pH range of the gastric acid produced in the stomach?

    <p>pH 1.5-2 (D)</p> Signup and view all the answers

    Which vitamins are produced by bacteria in the large intestine?

    <p>K, B5, Biotin (C)</p> Signup and view all the answers

    Which enzyme is activated by hydrochloric acid in the stomach?

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

    What is the primary role of the rectum in the digestive system?

    <p>Temporary storage of feces (D)</p> Signup and view all the answers

    What role does the pancreas serve in digestion?

    <p>It has both endocrine and exocrine functions. (D)</p> Signup and view all the answers

    What neutralizes the hydrochloric acid that enters the duodenum?

    <p>Bicarbonate from pancreatic juice (C)</p> Signup and view all the answers

    Which of the following indicates that a protease is inactive?

    <p>It starts with 'pro-'. (B)</p> Signup and view all the answers

    What is the primary role of glucagon in the body?

    <p>To increase blood glucose levels by promoting glycogenolysis (B)</p> Signup and view all the answers

    What is produced as a byproduct of protein catabolism?

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

    Which hormone is released in response to stress and increases blood glucose levels?

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

    What is the process of forming peptide bonds between amino acids called?

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

    What do metabolic intermediates from amino acid processing contribute to?

    <p>Energy production through the Krebs cycle (A)</p> Signup and view all the answers

    Which of the following is NOT a function of the thyroid hormone?

    <p>Stimulating gluconeogenesis directly (D)</p> Signup and view all the answers

    Under what condition does the body primarily break down muscle protein?

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

    What role do ribosomes play in proteogenesis?

    <p>Serve as the site of protein synthesis (C)</p> Signup and view all the answers

    What is the primary function of mastication in the digestive process?

    <p>To increase the surface area of food particles (A)</p> Signup and view all the answers

    What role does the tongue play during mastication?

    <p>To push food against the teeth without being bitten (B)</p> Signup and view all the answers

    What is the term for the contractions that move food through the digestive tract?

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

    Once food enters the small intestine, what is it transformed into?

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

    What is the function of the pyloric sphincter during digestion?

    <p>To regulate the flow of chime into the duodenum (C)</p> Signup and view all the answers

    What initiates the process of chemical digestion in the mouth?

    <p>Action of digestive enzymes in saliva (D)</p> Signup and view all the answers

    Which part of the digestive system is primarily responsible for mixing and churning of the bolus?

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

    What is the effect of the arrival of food in the stomach?

    <p>Triggers a receptive relaxation response (C)</p> Signup and view all the answers

    What initiates fat digestion in the mouth?

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

    Which enzyme is primarily responsible for fat digestion in the small intestine?

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

    What is the primary role of bile in fat digestion?

    <p>Emulsifying fat droplets (B)</p> Signup and view all the answers

    At what pH range is pancreatic lipase most effective?

    <p>3 to 6 (B)</p> Signup and view all the answers

    Why does lingual lipase have a limited role in fat digestion?

    <p>Food remains in the mouth for a short time. (B)</p> Signup and view all the answers

    Which type of lipase is predominantly active in children?

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

    What happens to lingual lipase when food moves to the stomach?

    <p>It is inactivated. (A)</p> Signup and view all the answers

    What is the primary reason pancreatic lipase is more important than lingual lipase?

    <p>It acts for a longer duration in the digestive process. (B)</p> Signup and view all the answers

    Flashcards

    Digestive Tract Function

    The passageway for food from the oral cavity to the anus; it mechanically and chemically processes food for absorption.

    Accessory Digestive Organs

    Organs that produce secretions aiding digestion but are not part of the digestive tract, such as the pancreas, liver and Salivary glands.

    Oral Cavity Functions

    Ingestion, sensory analysis of food, lubrication, mechanical digestion (teeth, tongue), carbohydrate digestion (amylase), and lipid digestion (lipase).

    Liver Functions

    Metabolic regulation (blood glucose, ammonia), haematological regulation (plasma protein synthesis), and processing of toxins and nutrients.

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    Hepatic Portal System

    The network of blood vessels conveying blood from the digestive tract to the liver for processing.

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    Mechanical Processing (Digestion)

    Physical breakdown of food, like chewing and churning.

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    Blood flow from digestive tract

    Blood from the intestines flows to the liver through the hepatic portal system.

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    Serosa

    Outer layer of the digestive tract that covers the muscles external, mostly

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    Bile Emulsification

    Bile salts break down lipid droplets, increasing the surface area for lipase digestion.

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    Gallbladder Function

    Stores and concentrates bile before release into the small intestine.

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    Stomach Rugae

    Folds in the stomach wall that allow expansion during meals.

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    Parietal Cell Function

    Secrete HCl (stomach acid) and intrinsic factor for vitamin B12 absorption.

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    Chief Cell Function

    Produce pepsinogen, which becomes pepsin to digest proteins.

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    Pancreatic Juice Composition

    Contains bicarbonate for neutralizing stomach acid and digestive enzymes (lipase, amylase, proteases).

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    Inactive Pancreatic Enzymes

    Pancreatic proteases are initially produced in inactive forms (e.g., trypsinogen, proelastase) to prevent digestion of the pancreas itself.

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    Chyme

    Viscous, acidic mixture of partially digested food formed in the stomach.

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    Small Intestine Function

    Absorbs nutrients from digested food, with a large surface area due to its length, circular folds, villi, and microvilli.

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    Duodenum Function

    First part of small intestine, neutralising stomach acid and receiving chyme and digestive secretions from pancreas and liver.

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    Jejunum Function

    Middle part of small intestine, primary site for chemical digestion and nutrient absorption.

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    Ileum Function

    Last part of small intestine, controls flow of digested food to colon through ileocecal valve.

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    Large Intestine Function

    Compacts and stores fecal material, absorbs water and electrolytes, produces vitamins.

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    Cecum Function

    Expandable pouch that receives chyme from the ileum and starts compaction of feces.

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    Colon Regions

    Ascending, transverse, descending, and sigmoid colon; largest section of large intestine responsible for reabsorbing water and electrolytes to compact the waste.

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    Mechanical Digestion

    Physical breakdown of food, not always necessary after initial digestion.

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    What is mastication?

    The process of chewing food using teeth and tongue to break down large pieces into smaller ones for easier swallowing.

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    What does the palate do?

    The palate, the roof of your mouth, allows you to breathe through your nose while chewing food.

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    What is peristalsis?

    Wave-like muscle contractions that push food through your digestive tract.

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    What is the role of the stomach?

    The stomach churns and mixes food with gastric juices to start digestion.

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    What is chyme?

    Partially digested food that is mixed with gastric juices in the stomach. It resembles a thick porridge.

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    What does the small intestine do?

    The small intestine mixes chyme with digestive juices for further digestion and absorption of nutrients.

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    What is segmentation?

    A type of muscle contraction in the small intestine that mixes chyme with digestive juices.

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    What are the three functions of small intestine motility?

    It mixes chyme with digestive juices and bile, turns food into chyme, and increases contact between chyme and intestinal walls for absorption and digestion.

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    What is the first step in fat digestion?

    Fat digestion begins in the mouth with the enzyme lingual lipase.

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    Lingual Lipase

    An enzyme secreted by the tongue that starts the breakdown of fats in the mouth.

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    Why is lingual lipase inactivated in the stomach?

    The acidic environment of the stomach inactivates lingual lipase due to its limited pH range.

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    Pancreatic Lipase

    The primary enzyme responsible for fat digestion, secreted by the pancreas and active in the small intestine.

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    What is the role of bile in fat digestion?

    Bile emulsifies fat, breaking large fat droplets into smaller ones, increasing surface area for pancreatic lipase to act.

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    Why is bile important?

    Bile increases the surface area of fat for pancreatic lipase to work on, which leads to more efficient fat breakdown.

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    Why does fat digestion primarily occur in the small intestine?

    The small intestine provides the ideal environment with pancreatic lipase and bile, allowing for efficient fat breakdown.

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    What makes fat digestion different from carbohydrate and protein digestion?

    Unlike carbohydrates and proteins, fat digestion has only one major conversion step, from triglycerides to monoglycerides and fatty acids.

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    Amino Acid Recycling

    Worn-out cells break down into amino acids, which are then reused to build new proteins.

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    Liver's Amino Acid Role

    The liver can convert amino acids into fatty acids or glucose, depending on the body's needs.

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    Starvation and Protein Breakdown

    During starvation, the body breaks down muscle protein into amino acids, which are then used to produce glucose for energy.

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    Amino Acids and Energy Production

    Amino acids are broken down into metabolic intermediates like pyruvate and acetyl-CoA, which fuel energy production through the Krebs cycle.

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    Ammonium Ion Toxicity

    Protein catabolism (breakdown) produces toxic ammonium ions, which are converted to urea in the liver for safe elimination.

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    Protein Anabolism

    Protein synthesis (creating new proteins) is essential for growth and repair. It involves linking amino acids together, requiring energy and direction from DNA and RNA.

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    Thyroid's Role in Metabolism

    The thyroid gland produces thyroid hormone, which influences metabolic rate by increasing ATP production and affecting genes.

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    Hormonal Control of Metabolism

    Hormones like glucagon, cortisol, and adrenaline regulate metabolic processes, primarily by controlling blood glucose levels through glycogen breakdown, glucose synthesis, and fat breakdown.

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    Study Notes

    Digestive System Functions

    • Ingestion: Food and liquids enter the oral cavity, an active process.
    • Secretion: Digestive tract and glandular organs release water, acids, enzymes, buffers, and salts. This aids digestion and absorption, provides a defense against digestive acids/enzymes and mechanical stresses, and protects against swallowed bacteria.
    • Mechanical processing: Physical breakdown of food into smaller particles to allow for easier transport and increased surface area for enzyme action.
    • Digestion: Chemical breakdown of food into absorbable molecules.
    • Absorption: Movement of organic molecules, electrolytes, vitamins, and water across the digestive epithelium into interstitial fluid, then blood or lymph.
    • Defecation: Elimination of solid wastes.

    Digestive Tract Layers

    • Mucosa: Inner lining, composed of epithelium for absorption. Varied epithelium based on locations and stressors. (e.g. stratified squamous in oral cavity, simple columnar in absorption areas).
    • Submucosa: Irregular connective tissue, contains blood vessels, lymphatic vessels, and sensory neurons, and glands that secrete buffers and enzymes.
    • Muscularis externa: Dominated by smooth muscle. Inner circular muscles aid in agitation and valve formation, outer longitudinal muscles aid in movement.
    • Serosa: Covers the muscularis externa in many parts of the digestive tract.

    Organs

    • Oral cavity: Ingestion, sensory analysis, lubrication, mechanical digestion (chewing), initiation of carbohydrate and lipid digestion.
    • Stomach: Distensible organ that connects the esophagus to the duodenum. Temporarily stores ingested food. Contains gastric glands with parietal and chief cells that secrete intrinsic factor and HCl (for B12 absorption and protein breakdown). Chief cells release pepsinogen (converted to pepsin by HCl). Produces alkaline mucus to protect the stomach lining. Mechanical digestion occurs in stomach.
    • Pancreas: Both endocrine and exocrine. Endocrine portion releases hormones (insulin, glucagon) into the blood. Exocrine portion releases pancreatic juice into the duodenum (including bicarbonate to neutralize stomach acid, and digestive enzymes: lipase, amylase, protease).
    • Small intestine: Divided into duodenum, jejunum, and ileum. Has large surface area for nutrient absorption (circular folds, villi, microvilli). Receives chyme, digestive secretions (pancreatic, liver). Primary site of digestion and nutrient absorption.
    • Large intestine: Begins at the end of the ileum, and ends at the anus. Divided into the Cecum, Colon (ascending, transverse, descending, sigmoid), Rectum, and Anal canal. Compacts and stores fecal material, reabsorbs water and electrolytes, produces vitamins, and excretes waste.

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    Description

    This quiz explores the essential functions of the digestive system, including ingestion, secretion, mechanical processing, digestion, absorption, and defecation. Additionally, it covers the layers of the digestive tract, particularly the mucosa and its varying epithelium types. Test your knowledge on how these processes work together to support bodily functions.

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