chapter 15. quiz 1. Anatomy of the Gastrointestinal Tract
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Questions and Answers

What percentage of the total human body mass does the GI tract constitute?

  • 15%
  • 5% (correct)
  • 10%
  • 1%

    • What is the primary function of the serous fluid secreted by the serosa?

  • To regulate blood flow to the gut
  • To modulate gut motility
  • To reduce friction between muscle movements (correct)
  • To facilitate digestion

    • What is the function of the longitudinal muscle layer in the GI tract?

  • To shorten the length of the intestinal segment (correct)
  • To facilitate gut excretion
  • To increase the diameter of the intestinal lumen
  • To regulate gut absorption

    • What is the location of the myenteric (Auerbach) plexus in the GI tract?

    <p>Between the longitudinal muscle layer and circular muscle layer</p> Signup and view all the answers

    What is the function of the submucosal (Meissner) plexus in the GI tract?

    <p>To transmit information from the epithelium to the CNS</p> Signup and view all the answers

    What is the innermost layer of the GI tract wall?

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

    What is the primary function of the muscularis mucosa in the mucosa?

    <p>To move the villi</p> Signup and view all the answers

    Which part of the autonomic nervous system is primarily inhibitory to GI motility?

    <p>Sympathetic nervous system</p> Signup and view all the answers

    What is the primary neurotransmitter of the parasympathetic nervous system in the GI tract?

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

    Where do the preganglionic fibers of the sympathetic nervous system originate?

    <p>T5 to L2 segments of the spinal cord</p> Signup and view all the answers

    Which nerve fibers innervate the second half of the large intestine, sigmoid, rectal, and anal regions?

    <p>Pelvic nerve fibers</p> Signup and view all the answers

    What is the function of the lamina propria in the mucosa?

    <p>To contain blood vessels, nerve endings, and immune and inflammatory cells</p> Signup and view all the answers

    What is the primary function of the myenteric plexus in the GI tract?

    <p>Control motility</p> Signup and view all the answers

    What is the effect of sympathetic stimulation on the GI tract?

    <p>It increases the tone of the intestinal wall and induces contractions</p> Signup and view all the answers

    What is the role of interstitial cells of Cajal in the GI tract?

    <p>They generate intrinsic electrical activity of the GI tract</p> Signup and view all the answers

    How do sympathetic and parasympathetic stimulation affect the enteric nervous system?

    <p>Sympathetic stimulation is inhibitory, while parasympathetic stimulation is excitatory</p> Signup and view all the answers

    What is the mechanism by which sympathetic stimulation inhibits the release of acetylcholine, increases the tone of the wall and contract the sphincter ?

    <p>Through α-2 activation and β activation</p> Signup and view all the answers

    What is the effect of parasympathetic stimulation on the GI tract?

    <p>It decreases the tone of the intestinal wall and induces contractions</p> Signup and view all the answers

    What is the approximate length of the esophagus?

    <p>18 to 25 cm</p> Signup and view all the answers

    Which region of the esophagus is approximately 4 to 5 cm long and is surrounded by the trachea anteriorly?

    <p>Cervical esophagus</p> Signup and view all the answers

    In which region of the esophagus does it deviate to the right to allow room for the aortic arch?

    <p>Thoracic esophagus</p> Signup and view all the answers

    What is the composition of the upper one-third of the esophagus?

    <p>Striated muscle</p> Signup and view all the answers

    What is the location of the upper esophageal sphincter (UES)?

    <p>Level of the cricoid cartilage</p> Signup and view all the answers

    What is the range of the resting tone of the upper esophageal sphincter (UES)?

    <p>30-200 mm Hg</p> Signup and view all the answers

    What is the main component of the lower esophageal sphincter (LES)?

    <p>Circular esophageal muscle and diaphragm muscle</p> Signup and view all the answers

    What is the primary function of the upper esophageal sphincter (UES) in relation to food movement?

    <p>Coordinating with pharyngeal pushing of food downstream</p> Signup and view all the answers

    What is the range of the resting tone of the lower esophageal sphincter (LES)?

    <p>10-45 mm Hg</p> Signup and view all the answers

    Which muscles make up the upper esophageal sphincter (UES)?

    <p>Cricopharyngeal, inferior constrictor, and circular esophageal muscles</p> Signup and view all the answers

    What type of innervation does the lower esophageal sphincter (LES) have?

    <p>Both sympathetic and parasympathetic innervation</p> Signup and view all the answers

    What is the primary function of the proximal stomach?

    <p>Produce smooth, tonic contractions</p> Signup and view all the answers

    What is the minimum particle size required for food to enter the small intestine?

    <p>2 mm or less</p> Signup and view all the answers

    Which cell type in the stomach produces hydrochloric acid?

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

    What is the capacity of the stomach to store food?

    <p>Up to 1.5–2 liters</p> Signup and view all the answers

    What is the outcome of the stomach's digestive process on food?

    <p>Break down into chyme and reduce particle size</p> Signup and view all the answers

    What is the primary function of mucous cells in the stomach?

    <p>To protect against harsh hydrochloric acid</p> Signup and view all the answers

    What is the primary function of chief cells in the stomach?

    <p>To secrete pepsin</p> Signup and view all the answers

    What is the minimum particle size required for food to enter the small intestine?

    <p>2 mm or less</p> Signup and view all the answers

    Which cell type in the stomach secretes gastrin?

    <p>G cells</p> Signup and view all the answers

    What is the level of the vertebrae at which the esophagus extends from the hypopharynx?

    <p>C6</p> Signup and view all the answers

    What is the length of the cervical esophagus?

    <p>4-5 cm</p> Signup and view all the answers

    Where does the thoracic esophagus lie in relation to the trachea?

    <p>Posterior to the trachea</p> Signup and view all the answers

    What is the level of the vertebrae at which the esophagus runs anterior to the aorta?

    <p>T8 to T10</p> Signup and view all the answers

    What is the name of the junction where the esophagus ends?

    <p>Gastroesophageal (GE) junction at the T11 level.</p> Signup and view all the answers

    Where do the digestive enzymes from the pancreas, liver, and gallbladder enter the small intestine?

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

    What percentage of available nutrients are absorbed by the jejunum ?

    <p>90%</p> Signup and view all the answers

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

    <p>Absorption of nutrients</p> Signup and view all the answers

    What is the purpose of the ileocecal valve?

    <p>To prevent reflux of colonic contents into the small intestine</p> Signup and view all the answers

    How does the jejunum increase its surface area for absorption?

    <p>By folding its walls many times over</p> Signup and view all the answers

    absorbtion of vitamin B12 occur mainly in ?

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

    What is the primary function of the cecum in the large intestine?

    <p>To mix the chyme from the small intestine with bacteria to form fecal matter</p> Signup and view all the answers

    What is the function of the contractions of the transverse colon?

    <p>To mix the feces and allow bacteria to ferment the waste</p> Signup and view all the answers

    What is the primary function of the sigmoid colon?

    <p>To transport the fecal matter from the descending colon to the rectum and anus</p> Signup and view all the answers

    What happens when fecal matter accumulates in the rectum?

    <p>It activates stretch receptors and leads to relaxation of the internal anal sphincter</p> Signup and view all the answers

    What is the role of the ascending colon in the large intestine?

    <p>To transport the fecal matter superiorly along the right side</p> Signup and view all the answers

    What happens to the fecal matter in the transverse colon?

    <p>It is mixed and allowed to ferment by bacteria</p> Signup and view all the answers

    Study Notes

    • The esophagus is a muscular tube that connects the pharynx to the stomach, measuring approximately 18-25 cm in length.
    • The esophagus extends from the level of the hypopharynx at the C6 vertebrae down to the gastroesophageal (GE) junction at the T11 level.
    • The esophagus has three regions: cervical, thoracic, and abdominal, with the cervical esophagus being approximately 4-5 cm long and surrounded by the trachea, vertebral column, carotid sheaths, and thyroid gland.
    • The upper one-third of the esophagus is composed of striated muscle, and the remaining two-thirds is smooth muscle.
    • There are two areas of high pressure in the esophagus: the upper esophageal sphincter (UES) and the lower esophageal sphincter (LES), with resting tone ranging from 30-200 mm Hg for the UES and 10-45 mm Hg for the LES.
    • The stomach is a J-shaped dilation of the alimentary tract, divided into four regions: the cardia, fundus, body or corpus, and antrum.
    • The stomach has three main functions: storing large quantities of food, mixing food with gastric secretions to form chyme, and slowing emptying into the small intestine.
    • Notable cell types in the stomach that aid in digestion include mucous cells, parietal cells, chief cells, and G cells, which together break down and partially digest food into chyme.
    • The duodenum is the first and smallest section of the small intestine, measuring between 25-30 cm long, and forms a C-shaped loop around the pancreas.
    • The duodenum's main function is to chemically digest the chyme received from the stomach in preparation for absorption, with the pancreas, liver, and gallbladder secreting digestive enzymes through the ampulla of Vater.
    • The jejunum is the second section of the small intestine, and its primary function is to absorb nutrients, with the walls of the jejunum folded many times over to increase its surface area for maximal absorption.
    • The ileum is the final section of the small intestine, serving to absorb vitamin B12 and other products of digestion that were not previously absorbed in the jejunum.
    • The large intestine is composed of the cecum, appendix, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum.
    • The GI tract constitutes approximately 5% of the total human body mass, with its main functions being motility, digestion, absorption, excretion, and circulation.
    • The layers of the GI tract wall, from outermost to innermost, are the serosa, longitudinal muscle layer, circular muscle layer, submucosa, and mucosa.
    • The autonomic nervous system innervates the GI tract, composed of the extrinsic nervous system (with sympathetic and parasympathetic components) and the enteric nervous system.
    • The extrinsic sympathetic nervous system is primarily inhibitory, with stimulation decreasing or ceasing GI motility, while the extrinsic parasympathetic nervous system is primarily excitatory, activating GI motility and function.
    • The enteric nervous system is the independent nervous system of the GI tract, controlling motility, secretion, and blood flow, with two plexuses: the myenteric (Auerbach) plexus and the submucosal (Meissner) plexus.

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    Test your knowledge of the structure and functions of the gastrointestinal tract, including its layers and main functions. Learn about the different parts of the GI tract and their roles in digestion, absorption, and excretion. Challenge yourself with this quiz!

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