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Indietro

Digestive System Anatomy & Physiology - Chapter 24

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Termini in questo insieme (28)

  • What are the major layers of the digestive tract from innermost to outermost?

    Mucosa, submucosa, muscularis, and serosa.

  • What is the primary function of the muscularis layer in the digestive tract?

    It enables mechanical digestion through muscle contractions like peristalsis and segmentation.

  • How does the epithelial type vary along the digestive tract and why?

    It changes from stratified squamous in the mouth and esophagus for protection to simple columnar in the stomach and intestines for secretion and absorption.

  • What is peristalsis and what would happen if it were impaired?

    Peristalsis is wave-like muscle contractions moving food along the tract; impairment would cause slowed or blocked food movement.

  • What role do the visceral and parietal peritoneum play in digestion?

    They are serous membranes that reduce friction and support digestive organs with peritoneal fluid.

  • What are the main functions of the oral cavity in digestion?

    Initiates digestion mechanically via teeth and tongue, and chemically via salivary enzymes.

  • What components are found in saliva and their functions?

    Saliva contains enzymes (e.g., amylase), buffers, antibodies, and mucins to lubricate and begin digestion.

  • Describe the phases of swallowing.

    Buccal (voluntary), pharyngeal (reflexive airway protection), and esophageal (peristalsis to stomach).

  • What is the function of the lower esophageal sphincter (LES)?

    It prevents stomach acid and contents from refluxing into the esophagus.

  • Name the four regions of the stomach and their significance.

    Cardia (entry), fundus (storage), body (mixing), and pylorus (controls chyme exit).

  • How do the three muscular layers of the stomach aid digestion?

    They allow churning and mixing of food with gastric secretions for mechanical digestion.

  • What are the roles of mucous cells, parietal cells, chief cells, and G-cells in the stomach?

    Mucous cells secrete mucus, parietal cells secrete HCl, chief cells secrete pepsinogen, and G-cells secrete gastrin.

  • How does the stomach protect itself from self-digestion?

    By secreting a thick mucus layer and maintaining tight junctions in the epithelium.

  • What is the function of hydrochloric acid (HCl) in the stomach?

    It activates pepsinogen to pepsin and kills pathogens.

  • What are the three phases of gastric regulation?

    Cephalic (brain), gastric (stomach), and intestinal (intestine) phases regulate secretion and motility.

  • How do meal compositions affect gastric emptying rates?

    Fats slow gastric emptying more than carbohydrates or proteins.

  • What enzymes are found in pancreatic juice and their functions?

    Amylase digests carbs, lipase digests fats, nucleases digest nucleic acids, and proteases digest proteins.

  • Why are pancreatic proteases secreted in inactive forms?

    To prevent autodigestion of the pancreas; they are activated in the small intestine.

  • How do secretin and CCK regulate pancreatic and bile secretions?

    Secretin stimulates bicarbonate release; CCK stimulates enzyme and bile secretion.

  • What structures increase the surface area of the small intestine for absorption?

    Circular folds, villi, and microvilli greatly increase absorptive surface area.

  • What is the role of brush border enzymes?

    They complete the final digestion of carbohydrates and proteins at the intestinal surface.

  • Describe the process of lipid digestion and absorption in the small intestine.

    Emulsification by bile, micelle formation, and absorption via lacteals into lymph.

  • What happens if the villi in the small intestine are severely damaged?

    Malabsorption occurs, leading to nutrient deficiencies and digestive issues.

  • What are the major regions of the large intestine?

    Cecum, colon segments (ascending, transverse, descending, sigmoid), rectum, and anal canal.

  • What is the function of taenia coli and haustra in the large intestine?

    Taenia coli are muscle bands that create haustra, pouches aiding in segmentation and motility.

  • How do bacteria in the large intestine contribute to nutrition?

    They synthesize vitamins K, biotin, and B12.

  • What is the defecation reflex and how do internal and external sphincters differ?

    The reflex triggers stool expulsion; the internal sphincter is involuntary, the external sphincter is voluntary.

  • How does dietary fiber influence colonic motility and fecal formation?

    Fiber increases bulk and stimulates motility, aiding fecal formation and regularity.