Small Intestinal Motility Quiz
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Small Intestinal Motility Quiz

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Questions and Answers

What is the form of iron that is absorbed into intestinal cells?

  • Fe2+ (ferrous) (correct)
  • Transferrin
  • Ferritin
  • Fe3+ (ferric)

    • What happens to excess iron that is not absorbed into the blood?

  • It is sloughed off as cell debris.
  • It is excreted in feces.
  • It is stored in the liver.
  • It is converted to ferritin. (correct)

    • What initiates the formation of water-soluble chylomicrons in fat absorption?

  • Coating with apoproteins (correct)
  • Diffusion through cell membrane
  • Fusion with lysosomes
  • Exocytosis of amino acids

    • In the process of iron absorption, what is the role of transferrin?

    <p>To transport iron in the blood</p> Signup and view all the answers

    Where is iron primarily absorbed in the gastrointestinal tract?

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

    What does the coating of chylomicrons with apoproteins facilitate?

    <p>Water solubility and transport</p> Signup and view all the answers

    Which form of iron is not absorbable and cannot be taken up by intestinal cells?

    <p>Fe3+ (ferric)</p> Signup and view all the answers

    What is the main consequence of sloughing off intestinal epithelial cells?

    <p>Loss of dietary iron</p> Signup and view all the answers

    Which statement about the effects of PNS and SNS on SI contraction is correct?

    <p>PNS increases contraction while SNS decreases it.</p> Signup and view all the answers

    How do the rates of segmentation differ between the duodenum and ileum?

    <p>Duodenum has a higher rate than ileum at 12/min vs 9/min.</p> Signup and view all the answers

    What is the role of the ileocecal sphincter when pressure is applied on the cecal side?

    <p>It contracts to prevent bacteria-laden LI contents from entering the SI.</p> Signup and view all the answers

    Where are dietary disaccharides primarily broken down?

    <p>At the brush border membrane by brush border enzymes.</p> Signup and view all the answers

    What mechanism is required for the absorption of single amino acids in the small intestine?

    <p>Na-dependent active transport.</p> Signup and view all the answers

    What initial processes lead to the formation of disaccharides in carbohydrate absorption?

    <p>Action of salivary and pancreatic amylase on polysaccharides</p> Signup and view all the answers

    Which type of transport is primarily involved when glucose and galactose are absorbed into the epithelial cells?

    <p>Na+-dependent active transport</p> Signup and view all the answers

    What type of transport allows for the absorption of fructose in the carbohydrate absorption process?

    <p>Facilitated diffusion</p> Signup and view all the answers

    Which enzymes are responsible for converting disaccharides into monosaccharides in carbohydrate absorption?

    <p>Maltase, lactase, and sucrase</p> Signup and view all the answers

    How is sodium involved in the process of carbohydrate absorption?

    <p>It is an energy source for monosaccharide absorption</p> Signup and view all the answers

    What is the final destination of absorbed monosaccharides after passing through the intestinal epithelial cells?

    <p>Entered into the bloodstream</p> Signup and view all the answers

    What role does facilitated diffusion play in carbohydrate absorption?

    <p>It facilitates the transport of monosaccharides into the capillaries</p> Signup and view all the answers

    Which type of carbohydrates can be first broken down by salivary amylase?

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

    What is the primary function of cotransport in carbohydrate absorption?

    <p>Driving the uptake of glucose and galactose using sodium gradient</p> Signup and view all the answers

    Which of the following describes the process that requires energy during carbohydrate absorption?

    <p>Cotransport of sodium and glucose</p> Signup and view all the answers

    What is another name for enterokinase?

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

    Which enzyme is produced from the activation of trypsinogen?

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

    Which of the following correctly describes amino acids transport?

    <p>Via Na+-amino acid co-transporters</p> Signup and view all the answers

    What type of transport mechanism is used for di- and tripeptides absorption?

    <p>H+-dependent co-transporters</p> Signup and view all the answers

    What role do brush border membrane enzymes (BBE) have in oligopeptide digestion?

    <p>Digesting oligopeptides into amino acids</p> Signup and view all the answers

    Which enzyme completes protein digestion by hydrolyzing small peptide fragments?

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

    Which enzyme is NOT involved in the initial stages of protein digestion?

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

    How do small peptides get absorbed in the intestinal cells?

    <p>Through H+-dependent cotransporters</p> Signup and view all the answers

    What is the primary function of carboxypeptidase in protein digestion?

    <p>Converting polypeptides into dipeptides</p> Signup and view all the answers

    What is the primary mechanism for the absorption of amino acids in the intestine?

    <p>Na+-amino acid co-transporters</p> Signup and view all the answers

    What is the primary function of segmentation in the small intestine?

    <p>To mix and slowly propel chyme for absorption</p> Signup and view all the answers

    What initiates segmentation contractions in the small intestine?

    <p>Pacesetter cells in the GIT walls</p> Signup and view all the answers

    Which segment of the small intestine exhibits faster segmentation contractions?

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

    What role does the gastroileal reflex play in the small intestine?

    <p>Stimulates segmentation in the ileum</p> Signup and view all the answers

    How often do migrating motility complexes occur in the small intestine?

    <p>Every 1.5 hours</p> Signup and view all the answers

    What is the main activity of migrating motility complexes?

    <p>A cleaning wave to move remnants towards the colon</p> Signup and view all the answers

    The segmentation contractions in the small intestine primarily occur between which types of muscle layers?

    <p>Circular and longitudinal smooth muscle layers</p> Signup and view all the answers

    What triggers the increase in segmentation contractions in the duodenum?

    <p>Local distension from incoming chyme</p> Signup and view all the answers

    What is the expected duration for contents to move through the small intestine?

    <p>3-5 hours</p> Signup and view all the answers

    What occurs to segmentation contractions when a new meal is introduced?

    <p>They stop temporarily for peristaltic waves</p> Signup and view all the answers

    Study Notes

    Small Intestinal Motility

    • Segmentation is the primary form of motility during meal digestion, mixing and slowly propelling chyme
    • Segmentation is driven by oscillating contractions of the circular smooth muscle layer along the length of the intestine
    • Segmentation is characterized by contracted segments alternating with relaxed areas where chyme is located
    • The rate of segmentation contractions is higher in the duodenum than the ileum (proximal faster than distal)
    • Migrating Motility Complex (MMC): occurs when most of the meal is absorbed, and segmentation contractions stop
    • The MMC is a repetitive, peristaltic wave that occurs every 1.5 hours and is more of a clean-up type motility
    • The MMC is initiated by small intestinal pacesetter cells within the GIT walls
    • The duodenum segments are stimulated by local distension, while the ileum segments are stimulated by gastrin. This is known as the gastroileal reflex.
    • Chyme in the stomach is the major stimulus for gastrin release

    Carbohydrate Absorption

    • Dietary carbohydrates (starch, glycogen, lactose, sucrose) are broken down into monosaccharides (glucose, galactose, fructose) in the small intestine
    • Salivary amylase begins the breakdown of polysaccharides in the mouth, while pancreatic amylase continues the process in the small intestine
    • Disaccharides are broken down into monosaccharides by brush border membrane enzymes (maltase, lactase, sucrase)
    • Monosaccharides are absorbed into the small intestinal epithelial cells through active transport (glucose, galactose) and facilitated diffusion (fructose)
    • Glucose and galactose are absorbed by sodium-dependent active transport
    • Fructose is absorbed by facilitated diffusion

    Protein Digestion & Absorption

    • Proteins are digested into smaller peptides by pancreatic enzymes (trypsin, chymotrypsin, carboxypeptidase)
    • Brush border membrane enzymes (aminopeptidases) complete protein digestion by breaking down small peptide fragments into amino acids
    • Amino acids are absorbed into the small intestinal epithelial cells by sodium-dependent active transport
    • Di and tripeptides are absorbed by H+-dependent cotransporters
    • Oligopeptides require further breakdown by brush border membrane enzymes before absorption

    Fat Absorption

    • Dietary fat is converted into chylomicrons
    • Chylomicrons are assembled within intestinal cells
    • Lipid droplets (TG) are coated with apoproteins in the gut
    • Chylomicrons are exocytosed from the small intestine into the lymphatic system

    Brush Border Membrane Enzymes

    • Enterokinase (enteropeptidase): Activates pancreatic trypsinogen to produce trypsin, chymotrypsin, and carboxypeptidase
    • Aminopeptidases: Complete protein digestion
    • These enzymes are crucial for the final stages of digestion and efficient absorption of nutrients

    Iron Absorption

    • Ferrous iron (Fe2+) is absorbed in the small intestine
    • Ferric iron (Fe3+) is not absorbed
    • Dietary iron is absorbed into small intestinal epithelial cells
    • Some absorbed iron is stored in the cell as ferritin, and some is transported into the blood
    • Iron in the blood is bound to transferrin, a protein that transports iron throughout the body

    True/False Statements

    • False: The rate of duodenum and ileum segmentation is not the same. The duodenum's segmentation rate is higher than the ileum's (12/min vs. 9/min).
    • False: The ileocecal sphincter does not contract more with pressure on the cecal side. It normally contracts to prevent backflow of bacteria-laden colonic contents into the small intestine.
    • True: Dietary disaccharides are broken down at the brush border membrane (BBM) by brush border enzymes (BBEs).
    • False: Pancreatic amylase also aids in the digestion of polysaccharides, not just salivary amylase.
    • True: Single amino acid absorption requires sodium-dependent active transport, while di- and tripeptides utilize H+-dependent cotransport.
    • True: In small intestinal epithelial cells, monoglycerides (MGs) and free fatty acids (FFAs) re-esterify to form triglycerides (TGs).

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    Small Intestine Lecture Notes Fall 2024 PDF

    Description

    Test your understanding of small intestinal motility, focusing on segmentation and the migrating motility complex (MMC). This quiz covers the physiological processes involved during digestion and the roles of various regulatory mechanisms. Challenge yourself to master the details of intestinal motility mechanisms.

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