Digestive System Chapter 26 Part 2
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Questions and Answers

What stimulates the secretion of enzymes from the pancreas?

  • The release of secretin
  • Stretching of the stomach wall (correct)
  • Food entering the intestines
  • Presence of alkaline bile

    • What role does the hormone cholecystokinin (CCK) play in digestion?

  • Stimulates gallbladder contraction and bile release (correct)
  • Inhibits peristalsis in the intestines
  • Triggers the secretion of alkaline pancreatic juices
  • Stimulates the release of enzymes from salivary glands

    • Which reflex is responsible for the urge to defecate after a meal?

  • Gastrocolic reflex (correct)
  • Pyloric reflex
  • Colorectal reflex
  • Enterogastric reflex

    • What is the primary function of the large intestine?

    <p>Absorption of water and electrolytes (C)</p> Signup and view all the answers

    What causes pancreatic cells to secrete the alkaline components of pancreatic juices?

    <p>Action of secretin from duodenal cells (C)</p> Signup and view all the answers

    What percentage of triglycerides can be digested by lingual and gastric lipases combined?

    <p>30% (D)</p> Signup and view all the answers

    Which enzyme is responsible for digesting triglycerides into monoglycerides and fatty acids in the small intestine?

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

    What is the role of bile salts in lipid digestion?

    <p>Emulsification of lipid droplets (B)</p> Signup and view all the answers

    What is the primary site of water absorption in the digestive system?

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

    Which hormone inhibits iron absorption in the body?

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

    How are fat-soluble vitamins absorbed in the small intestine?

    <p>Along with lipids in micelles (D)</p> Signup and view all the answers

    What is the absorbance mechanism of vitamin B12 in the small intestine?

    <p>Receptor-mediated endocytosis (D)</p> Signup and view all the answers

    Which of the following is NOT part of nucleic acid digestion?

    <p>Absorption via facilitated diffusion (C)</p> Signup and view all the answers

    What is the primary function of the rectum?

    <p>Storage of fecal matter prior to defecation (A)</p> Signup and view all the answers

    Which statement accurately describes the appendicitis condition?

    <p>It often results from fecal matter obstructing the appendix. (D)</p> Signup and view all the answers

    What role do rectal valves play in the digestive system?

    <p>They retain fecal matter during the passing of gas. (D)</p> Signup and view all the answers

    Which reflex is initiated by the distension of the stomach?

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

    What primarily initiates the urge to defecate?

    <p>Filling of the rectum (A)</p> Signup and view all the answers

    Which enzyme initiates protein digestion in the stomach?

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

    What determines the absorption of carbohydrates in the small intestine?

    <p>Cotransport with Na+ and facilitated diffusion (D)</p> Signup and view all the answers

    Which enzymes are involved in the digestion of proteins in the small intestine?

    <p>Pancreatic enzymes and brush border enzymes (C)</p> Signup and view all the answers

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

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

    What structure controls the entry of materials from the ileum into the large intestine?

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

    Which of the following statements about the duodenum is true?

    <p>It receives chyme from the stomach. (D)</p> Signup and view all the answers

    What digestive process primarily occurs in the jejunum?

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

    Which type of muscle contraction primarily propels chyme through the small intestine?

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

    What is the main function of Brunner's glands located in the duodenum?

    <p>Producing alkaline mucus (B)</p> Signup and view all the answers

    What type of cells are responsible for the secretion of pancreatic digestive enzymes?

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

    Which of the following enzymes is NOT produced by the pancreas?

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

    Which segment of the small intestine is primarily involved in lipid absorption?

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

    What condition is associated with the formation of gallstones?

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

    The liver primarily functions in the production of which digestive substance?

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

    Which structure is involved in the regulation of bile flow from the gallbladder?

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

    What is the primary role of lacteals in the small intestine?

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

    What triggers the gastroileal reflex?

    <p>Food entering the stomach (D)</p> Signup and view all the answers

    Flashcards

    Vagal Innervation

    Activation of the vagus nerve stimulates pancreatic enzyme secretion upon seeing, smelling, or tasting food.

    Secretin Release

    A hormone released from the duodenum that stimulates the pancreas to secrete alkaline fluid in response to acidic chyme.

    Cholecystokinin (CCK)

    A hormone secreted by the duodenum that triggers the release of digestive enzymes and bile in response to fatty acids and proteins.

    Functions of the Large Intestine

    Absorbs water and electrolytes, compacts chyme into feces, and stores feces until defecation.

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    Gastrocolic Reflex

    Reflex that increases peristalsis in the colon following stomach stretching due to food intake.

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    Anal Canal

    The terminal centimeters of the large intestine.

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    Rectum

    Storage of fecal matter prior to defecation.

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    Appendicitis

    Inflammation of the appendix, often due to fecal obstruction.

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    Peristalsis

    Weak and sluggish contractions in the large intestine compared to the small intestine.

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    Defecation Reflex

    Filling of the rectum triggers the urge to defecate.

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    Carbohydrate Digestion

    Breakdown of carbs into monosaccharides; occurs in oral cavity and small intestine.

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    Protein Digestion

    Breakdown of proteins into amino acids using specific enzymes.

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    Small Intestine

    A long tube beneath the stomach that absorbs nutrients and water.

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    Segments of Small Intestine

    The small intestine consists of duodenum, jejunum, and ileum.

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    Duodenum

    First segment of the small intestine, receives chyme from the stomach.

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    Jejunum

    Middle region of the small intestine, key for digestion and absorption.

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    Ileum

    Last segment of the small intestine, connects to the large intestine.

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    Circular Folds

    Internal folds in the small intestine that increase surface area.

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    Villi

    Fingerlike projections increasing surface area for absorption in the small intestine.

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    Lacteal

    Lymphatic capillary in villus responsible for absorbing lipids.

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    Microvilli

    Extensions of epithelial cells that form a brush border for increased absorption.

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    Motility

    Movement of chyme through the small intestine via segmentation and peristalsis.

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    Ileocecal Valve

    Sphincter controlling entry of materials from ileum to cecum.

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    Gallbladder

    Stores, concentrates, and releases bile for fat digestion.

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    Pancreas

    Produces insulin, glucagon, and pancreatic juice for digestion.

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    Pancreatic Juice

    Alkaline fluid containing digestive enzymes secreted by the pancreas.

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    Cholelithiasis

    Gallstones formed from cholesterol and bile salts.

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    Lingual lipase

    An enzyme in saliva activated in the stomach that begins lipid digestion.

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    Gastric lipase

    An enzyme produced by chief cells in the stomach that digests triglycerides into diglycerides and fatty acids.

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    Pancreatic lipase

    An enzyme released by the pancreas into the duodenum to digest triglycerides into monoglycerides and fatty acids.

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    Micelles

    Emulsified fat droplets that facilitate the absorption of fat-soluble vitamins in the intestine.

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    Hepcidin

    A hormone from the liver that regulates iron absorption based on iron levels in the body.

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    Vitamin B12 absorption

    Vitamin B12 is absorbed via receptor-mediated endocytosis requiring intrinsic factor produced by stomach parietal cells.

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    Water absorption in the small intestine

    The small intestine absorbs about 8 of 9 liters of ingested water, with the large intestine absorbing some.

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    Electrolyte absorption

    The small intestine absorbs almost all electrolytes, with iron absorption being the most regulated.

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    Study Notes

    Digestive System - Chapter 26 Part 2

    • Small Intestine Gross Anatomy:
      • A long tube inferior to the stomach, located medially in the abdominal cavity.
      • Nutrients reside here for at least 12 hours.
      • Absorbs most nutrients, a large percentage of water, electrolytes, and vitamins.
      • Coiled, thin-walled tube.
      • Extends from the pylorus to the cecum of the large intestine.
      • Consists of three segments: duodenum, jejunum, and ileum.

    Small Intestine - Segments

    • Duodenum:

      • First segment; originates at the pyloric sphincter.
      • C-shaped, surrounding the head of the pancreas.
      • Mostly retroperitoneal (initial portion is intraperitoneal).
      • Continuous with the jejunum at the duodenojejunal flexure.
      • Receives chyme (partially digested food) from the stomach.
      • Receives accessory gland secretions from the liver, gallbladder, and pancreas.

    • Jejunum:

      • Middle region, making up two-fifths of the small intestine's total length.
      • Primary region for chemical digestion and nutrient absorption.
      • Intraperitoneal, suspended by mesentery proper.

    • Ileum:

      • Last region, comprising three-fifths of the small intestine's length.
      • Distal end terminates at the ileocecal valve (regulates entry of materials into large intestine).
      • Intraperitoneal and suspended by mesentery proper.
      • Continues absorption of digested material.

    Small Intestine Tunics

    • Circular folds:

      • Internal mucosal and submucosal folds.
      • Increase surface area for enhanced nutrient absorption.
      • Act as "speed bumps" to slow the movement of chyme.
      • More numerous in the duodenum and jejunum, less common in the ileum.

    • Villi:

      • Finger-like projections of the mucosa.
      • Larger and more numerous in the jejunum.
      • Epithelial layer covering lamina propria.
      • Increased surface area assists absorption and secretion.
      • Contains an arteriole, capillary network, and lymphatic nodules (lacteals).

    • Microvilli:

      • Extensions of plasma membrane of simple columnar epithelial cells.
      • Increase surface area in the small intestine for increased absorption.
      • Contain various enzymes (brush border enzymes) that aid in digestion.
      • Proteins for digestion-product transport are also embedded here.
      • Lacteals absorb lipids and lipid-soluble vitamins

    • Submucosal gland (Brunner's glands):

      • Only found in the duodenum
      • Produces alkaline mucus to protect the duodenum from chyme

    Small Intestine Motility

    • Segmentation: Backward-and-forward motion, common in earlier stages of small intestine. More common than peristalsis.

      • Mixes chyme with gland secretions.
      • Moves chyme against new areas of brush border.
      • Regulates the motility of chyme in the earlier stages of the small intestine.

    • Peristalsis:

      • Propels chyme through the small intestine.
      • Successive waves of contractions migrating motility complex.
      • Relays on pacemaker cells and spreads through muscularis via gap junctions (similar to stomach).
      • Regulated by the ENS and ANS. Prevalent later in the intestinal phase.
      • Initiated by motilin, released from the duodenum.
      • Repeats until all content moved to large intestine (about 2 hours).

    Moving Chyme from Small Intestine into Large Intestine

    • Gastroileal reflex: Initiated when food enters the stomach.
      • Ileum contracts
      • Ileocecal sphincter relaxes
      • Cecum relaxes

    Accessory Digestive Organs

    • Gallbladder:

      • Sac-like organ attached to the inferior surface of the liver.
      • Stores, concentrates, and releases bile produced in the liver.
      • Bile aids in the digestion of fats
      • 3 tunics: inner mucosa, middle muscularis, external serosa
      • Mucosa with folds allowing for distension
      • Connected to common bile duct via cystic duct.

    • Pancreas:

      • Endocrine function: Produces and secretes insulin and glucagon.
      • Exocrine function: Produces pancreatic juice.
        • Pancreatic amylase: digests starch
        • Pancreatic lipase: digests triglycerides
        • Inactive proteases: digests proteins
        • Nucleases: digests nucleic acids
        • Alkaline fluid, rich in HCO3- and enzymes, aids in digestion

    Liver (Anatomy)

    • Gross anatomy:

      • Located in the right upper quadrant of the abdomen.
      • Covered by connective tissue capsule and visceral peritoneum.
      • Exceptions: a small bare area on the diaphragmatic surface.
      • Inferior vena cava seen on postero-inferior view.
      • Remnants of the ductus venosus are called the ligamentum venosum.

    • Hepatic artery & Hepatic portal vein:

      • Enters liver via porta hepatis.
      • The hepatic artery carries oxygenated blood and the hepatic portal vein carries nutrient-rich, deoxygenated blood
      • The blood mixes
      • Hepatic veins empty into the inferior vena cava.

    Liver (Histology)

    • Hepatic lobules: Functional units of the liver.
    • Hepatocytes: Main functional cells of the liver and arranged radially around a central vein.
    • Hepatic sinusoids: Blood-filled spaces between hepatocytes, facilitating exchange of materials between blood and liver cells.
    • Stellate cells (Kupffer cells): Macrophages in hepatic sinusoids that remove harmful substances.

    Lipid Digestion

    • Lingual lipase: In the mouth, breaks down lipids.
    • Gastric lipase: In the stomach, breaks down lipids.
    • Pancreatic lipase: In the small intestine, breaks down lipids
      • Bile salts aid by emulsification (breaking fat into smaller droplets).

    Nucleic Acid Digestion

    • Absorption: Active transport via membrane carriers.
    • Location: Absorbed in villi and transported to liver via hepatic portal vein.
    • Enzymes: Pancreatic ribonucleases and deoxyribonucleases.

    Water and Electrolyte Absorption

    • Water: Small intestine absorbs most dietary water, large intestine absorbs some.
    • Electrolytes: Small intestine absorbs almost all electrolytes and absorption depends on diet.
    • Hepcidin: Regulates iron absorption in the small intestine.

    Vitamin Absorption

    • Fat-soluble vitamins (A, D, E, K): Absorbed in small intestine alongside lipids in micelles.
    • Water-soluble vitamins (B and C): Absorbed through diffusion and active transport.
    • Vitamin B12: Absorbed by receptor-mediated endocytosis, requires intrinsic factor from stomach parietal cells.

    Large Intestine - Gross Anatomy

    • Cecum: Pouch at the beginning of the large intestine, receives chyme.
    • It has Omental appendices, Teniae coli and Rectum,
    • Ascending colon: Moves upward from the cecum.
    • Transverse colon: Moves across the abdomen.
    • Descending colon: Moves downward.
    • Sigmoid colon: S-shaped portion ending in the rectum
    • Rectum: Stores fecal matter prior to defecation.
    • Anal Canal: The terminal portion, which includes anal valves, anal canal, and sphincters.

    Large Intestine - Functions

    • Absorbs water and electrolytes from remaining digested material.
    • Compacts watery chyme into feces.
    • Stores feces until eliminated via defecation.
    • Contains resident flora.

    Large Intestine - Motility

    • Peristalsis: Weak and sluggish compared to the small intestine.
    • Churning: Distension stimulates reflex contractions in the muscular layers, moving contents.
    • Mass movements: Powerful contractions propel fecal material toward the rectum. Occur about 2 to 3 times a day, often after meals.

    Gastrocolic Reflex

    • Reflex that controls large intestine peristalsis.
      • Increased peristalsis when stomach stretches.
      • Causes an urge to defecate after a meal.

    Anal Canal

    • Rectum: Stores fecal matter before defecation.
    • Rectal Valves: Prevent fecal matter from passing during gas passage.
    • Anal Canal: Terminal centimeters of large intestine; contains smooth and skeletal muscle sphincters.
      • Internal anal sphincter: involuntary
      • External anal sphincter: voluntary.

    Clinical View: Appendicitis

    • Inflammation of the appendix, often due to fecal matter obstructing the appendix.
    • Appendix swells, blood supply compromised, bacterial growth possible.
    • May burst if untreated causing peritonitis (dangerous infection).
    • Initially, pain is referred to the area around the navel.
    • Later, the pain becomes localized to the right lower quadrant.
    • Common symptoms: Pain, nausea, vomiting, and abdominal tenderness.
    • Diagnosed and treated surgically through an appendectomy.

    Clinical View: Gallstones (Cholelithiasis)

    • Condensations of cholesterol or calcium salts in bile.
    • Majority asymptomatic until lodged in the cystic duct.
    • Gallbladder inflammation (cholecystitis) may occur.
    • Risk factors: Female sex, obesity, age, and Caucasian ethnicity.
    • Common symptoms: Severe pain in the right hypochondriac region, nausea, vomiting, indigestion, or bloating.
    • Symptoms often worsen after fatty meals.
    • May require surgical removal: cholecystectomy.

    Clinical View: Pancreatic Cancer

    • Cancer of pancreatic cells (often exocrine cells).
    • Early detection is difficult and is often not found until further along.
    • Poor prognosis if not detected early.
    • Symptoms in later stages include: abdominal pain, jaundice, loss of appetite, and weight loss.

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    Week 5 Chapt 26 Digestive Part 2 PDF

    Description

    Dive into the intricate details of the digestive system in Chapter 26 Part 2 with a focus on the small intestine's gross anatomy. Learn about the structure and function of its three main segments: duodenum, jejunum, and ileum. This quiz will test your understanding of nutrient absorption and the overall role of the small intestine.

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