Digestive Flashcards
Name Relevant parts of digestive system
-Mouth
-Pharynx
-Esophagus
-Lower esophageal sphincter
-Stomach
Pyloric sphincter
-Small intestine
-Ileocecal valve (Sphincter)
-Large intestine(colon)
-Rectum
-Anus
Cells in Mouth, Stomach,Small intestine (Duodenum, Jejunum and Ileum), Large intestine
-Mouth: Keratinocytes
-Stomach-Mucous, parietal, chief,endocrine
-Small intestine: Enterocytes, goblet,paneth,enteroendocrine,stem
Large intestine:Absorptive cells,goblet, stem
What are the four layers of the GI tract comprised of?
-Mucosa( epithelium, lamina propria, muscular mucosal)
-Submucosa
-Muscularis propria( Inner circular muscle layer, inter muscular space, outer longitudinal muscle layer)
-Serosa
Describe the digestive activities that occur in the mouth.
-Food broken down(mastication) through mechanical digestion
-Chemical digestion occurs as saliva containing amalase break down carbohydrates
-Bolus forms(mix of food and saliva)
-Swallow from mouth to pharynx to esophagus
Explain how the swallow reflex occurs.
Oral phase( voluntary): bolus formed, tongue pushes it toward pharynx
Pharyngeal phase(involuntary):bolus triggers sensory receptors in pharynx, soft palate elevated to seal off nasal cavity, larynx moves upwards and forward, epiglottis folds over glottis to prevent food in trachea
Esophageal phase(involuntary): Esophagus contracts pushing bolus down, LES relaxes, bolus enters stomach
-Controlled by swallowing center located in medulla oblongata
Explain how stomach acid is made and by which cell
-Primarily HCl, is secreted by parietal cells located in lining of stomach
Cells that produce HCl, pepsinogen, somatostatin, ghrelin, gastrin
-HCl: parietal
-Pepsinogen- Chief cells
-Somatostatin: D cells
Ghrelin:P/D1 cells
Gastrin: G Cells
Roles of HCl, pepsinogen, somatostatin, ghrelin, gastrin
HCl- creates acidic environments in stomach, denatures proteins, activates pepsinogen, aids in b12 absorption
Pepsinogen: Inactive precursor of pepsin, digestive enzyme, activated by HCl
Somatostatin: Inhibits release of other hormones and gastric acid secretion, acts as brake on digestion
Ghrelin- Simulates appetite, increases gastric motility and secretion
Gastrin: Stimulates GA secretion by parietal cells, promotes gastric motility and gastric mucosal growth
What roles do the liver, gall bladder and pancreas play in digestion and absorption of food?
Liver; makes bile that helps digest fats and vitamins
Pancreas: Makes digestive juice that breaks down carbohydrates, fats and proteins
Gallbladder: Stores bile between meals
Compare and contrast peristalsis and segmentation.
Peristalsis: slow movement, propels food and liquids along digestive tract in forward direction
-Contractions of circular and longitudinal muscles,wave like motion
Segmentation: Mixes food with digestive juice and aids in mechanical digestion
-Contracts circular muscles, churning
Describe the three extrinsic phases of GI regulation and what they do.
Cephalic: Stimulated by sight, smell, taste; activates vagus, pepsinogen, gastrin, histamine,HCl released
Gastric-Stimulated by food; more polypeptides and AA released
Intestinal- inhibits gastric activity when chyme enters SI; increase in osmolality and distinction
-Inhibits gastric motility and secretion and activity
Explain the importance of Enterohepatic Circulation.
-Substances like bile acids are excreted from liver into bile then reabsorbed from small intestine back to liver
-Maintains bile acid homeostasis, fat digestions and absorption, prolonging certain drug effects
Explain the digestive activities associated with the large intestine.
-Absorbs H20 and electrolytes, vitamin b and k and folic acid
Secretes h20 via active transport of NaCl into intestinal lumen
H20 absorption is due to osmotic gradient
-Forms feces
-Stores feces
Describe the rectal reflex and the role of the double sphincter of the anus.
Involves rectoanal inhibitory reflex( involuntary) relaxation of internal anal sphincter in response to rectal distention
-Double Sphincter allows for both involuntary continence and voluntary control of bowel movements
