Introduction to Digestive System
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Questions and Answers

What is the optimal pH necessary for the activation of salivary amylase?

  • 5.5
  • 6 (correct)
  • 7.5
  • 8.5

    • What is the function of mucin in saliva?

  • To regulate body temperature
  • To excrete waste products
  • To lubricate the bolus and facilitate swallowing (correct)
  • To facilitate digestion

    • What is the role of lingual lipase in saliva?

  • To digest carbohydrates
  • To digest milk fats (correct)
  • To appreciate taste
  • To regulate water balance

    • What is the primary function of the mouth?

    <p>Eating and ingestion of food materials</p> Signup and view all the answers

    What is the function of lysozyme in saliva?

    <p>To kill some bacteria</p> Signup and view all the answers

    What is the approximate volume of saliva secreted per day?

    <p>1000 ml to 1500 ml</p> Signup and view all the answers

    What is the pH range of saliva?

    <p>6.35 to 6.85</p> Signup and view all the answers

    What is the role of saliva in the appreciation of taste?

    <p>It dissolves solid food substances</p> Signup and view all the answers

    What type of enzyme is salivary amylase?

    <p>Carbohydrate-digestive</p> Signup and view all the answers

    What percentage of saliva is contributed by the Sub maxillary Gland?

    <p>70 %</p> Signup and view all the answers

    What is the specific gravity range of saliva?

    <p>1.002 to 1.012</p> Signup and view all the answers

    What is the role of saliva in the preparation of food for swallowing?

    <p>It moistens and lubricates the food</p> Signup and view all the answers

    What property does proline-rich saliva possess?

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

    What is the daily solid diet consumption of a normal young adult?

    <p>1 kg</p> Signup and view all the answers

    What is the function of digestion?

    <p>Breaking down food into simple chemical substances</p> Signup and view all the answers

    What is the tonicity of saliva with respect to plasma?

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

    What is the pH range of gastric juice?

    <p>0.9 to 1.2</p> Signup and view all the answers

    What is the specific gravity of pancreatic juice?

    <p>1.010 to 1.018</p> Signup and view all the answers

    What is the primary function of trypsin in protein digestion?

    <p>Converts caseinogen to casein</p> Signup and view all the answers

    What is the role of enterokinase in protein digestion?

    <p>Converts trypsinogen to active trypsin</p> Signup and view all the answers

    What is the primary function of pancreatic lipase in lipid digestion?

    <p>Breaks down triglycerides into monoglycerides and fatty acids</p> Signup and view all the answers

    What is the role of bile salts in lipid digestion?

    <p>Emulsifies fats</p> Signup and view all the answers

    What is the role of colipase in lipid digestion?

    <p>Acts as a coenzyme necessary for the pancreatic lipase to digest the dietary lipids</p> Signup and view all the answers

    What are the two functions of pancreatic juice?

    <p>Digestive and Neutralizing</p> Signup and view all the answers

    Which of the following substances is NOT excreted in saliva?

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

    What is the primary function of mucin in saliva?

    <p>Lubricating the mucus membrane of mouth</p> Signup and view all the answers

    During which condition does saliva excrete urea?

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

    What is the maximum capacity of the stomach?

    <p>1.5L</p> Signup and view all the answers

    What is the role of peristaltic movements in the stomach?

    <p>To mix the bolus with gastric juice</p> Signup and view all the answers

    What is the primary function of gastric juice in the stomach?

    <p>To act on proteins</p> Signup and view all the answers

    What is the role of saliva in speech?

    <p>To moisten and lubricate soft parts of the mouth and lips</p> Signup and view all the answers

    What happens to saliva secretion when body water content decreases?

    <p>It decreases</p> Signup and view all the answers

    What is the primary function of bile salts in the digestive system?

    <p>To keep cholesterol and lecithin in solution</p> Signup and view all the answers

    What is the result of bilirubin levels exceeding 2 mg/dl in plasma?

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

    What is the primary excretory product of bile?

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

    What is the function of bile in maintaining the pH of the GI tract?

    <p>It neutralizes the acid chyme entering the intestine</p> Signup and view all the answers

    What is the result of the absence of bile salts in the digestive system?

    <p>Gallstone formation</p> Signup and view all the answers

    What is the function of bile salts in the digestive system?

    <p>To inhibit the growth of certain bacteria in the lumen of the intestine</p> Signup and view all the answers

    What is the normal level of bilirubin in plasma?

    <p>0.5-1.5 mg/dl</p> Signup and view all the answers

    What is the function of bile salts in stimulating bile secretion?

    <p>Choleretic action</p> Signup and view all the answers

    Study Notes

    Introduction to Digestive System

    • Digestion is the process of breaking down food into simple chemical substances that can be absorbed and used as nutrients by the body.
    • A normal young adult consumes 1 kg of solid diet and 1-2 liters of fluid per day.
    • The functions of the digestive system include:
      • Ingestion of food substances
      • Breaking them into small particles
      • Transport of small particles to different areas of the digestive tract
      • Secretion of necessary enzymes and other substances for digestion
      • Digestion of the food particles
      • Absorption of the digestive products
      • Removal of unwanted substances from the body

    Functions of the Mouth

    • Primary functions of the mouth include:
      • Ingestion of food materials
      • Chewing of food and mixing it with saliva
      • Appreciation of taste of the food
      • Transfer of the food (bolus) to the esophagus by swallowing
    • Other functions of the mouth include:
      • Role in speech
      • Social functions such as smiling and other expressions

    Properties and Composition of Saliva

    • Volume: 1000-1500 ml per day is secreted
    • Reaction: Slightly acidic with pH 6.35-6.85
    • Specific gravity: 1.002-1.012
    • Saliva is hypotonic to plasma
    • Contribution of secretion of saliva by each major salivary gland:
      • Parotid gland: 25%
      • Submaxillary gland: 70%
      • Sublingual gland: 5%

    Functions of Saliva

    • Preparation of food for swallowing
    • Appreciation of taste
    • Digestive function
    • Cleansing and protective functions
    • Role in speech
    • Excretory function
    • Regulation of body temperature
    • Regulation of water balance

    Functions of Saliva (Digestive)

    • Saliva has 3 digestive enzymes: salivary amylase, maltase, and lingual lipase
    • Salivary amylase:
      • Acts on cooked or boiled starch and converts it into dextrin and maltose
      • Optimum pH for activation is 6
      • Cannot act on cellulose
    • Maltase:
      • Present only in traces in human saliva
      • Converts maltose into glucose
    • Lingual lipase:
      • Lipid-digesting (lipolytic) enzyme
      • Secreted from serous glands situated on the posterior aspect of the tongue
      • Digests milk fats
      • Hydrolyses triglycerides into fatty acids and diacylglycerol

    Functions of Saliva (Cleansing and Protective)

    • Rinses and keeps the mouth and teeth free of food debris
    • Enzyme lysozyme kills some bacteria such as staphylococcus, streptococcus, and brucella
    • Proline-rich saliva possesses antimicrobial property and neutralizes toxic substances such as tannins
    • Lactoferrin of saliva has antimicrobial property
    • Immunoglobulin IgA in saliva has antibacterial and antiviral actions
    • Mucin present in saliva protects the mouth by lubricating the mucus membrane of the mouth

    Functions of Stomach

    • Mechanical function:
      • Storage function: food is stored in the stomach for 3-4 hours and emptied into the intestine slowly
      • Formation of chyme: peristaltic movements of the stomach mix the bolus with gastric juice and convert it into a semisolid material known as chyme
    • Digestive function:
      • Proteolytic enzymes of gastric juice are pepsin and renin
      • Reaction: highly acidic with pH 0.9-1.2
      • Specific gravity: 1.002-1.004
    • Protective function
    • Hemopoietic function
    • Excretory function

    Pancreatic Juice

    • Properties:
      • Volume: 500-800 ml/day
      • Reaction: highly alkaline with pH 8-8.3
      • Specific gravity: 1.010-1.018
    • Functions:
      • Digestive function:
        • Digestion of proteins: major proteolytic enzymes are trypsin and chymotrypsin
        • Digestion of carbohydrates
        • Digestion of lipids: pancreatic lipase digests triglycerides into monoglycerides and fatty acids
      • Neutralizing function

    Bile

    • Prevention of gallstone formation: bile salts prevent the formation of gallstones by keeping cholesterol and lecithin in solution
    • Bile pigments:
      • Bilirubin and biliverdin are the two bile pigments
      • Bilirubin is the major bile pigment in human beings
      • Formed during the breakdown of hemoglobin
    • Functions:
      • Digestive function
      • Absorptive function
      • Excretory function
      • Laxative function
      • Antiseptic action
      • Choleretic action
      • Maintenance of pH in the GI tract
      • Prevention of gallstone formation
      • Lubrication function
      • Cholagogue action

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