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Ch. 21 Huma Phys
The Digestive System
| Question | Answer |
|---|---|
| 1. What is the function of the GI tract? | Move nutrients, water and electrolytes from the external environment to the internal environment, mass balance |
| 2. Name the four basic processes of the digestive system | Secretion, Absorption, Digestion, Motility |
| 3. Define digestion | Chemical/mechanical breakdown of food into smaller units to be taken across the intestinal epithelium into the body |
| Define absorption | Active/passive transfer of substances from lumen of GI to extracellular fluid |
| Define motility | Movement of material in GI caused by muscle contraction |
| What are the two components of secretion? | transepithelial transfer of water/ions from extracellular fluid to GI lumen and release of substances synthesized by GI epithelial cells |
| 4. What is GALT? | Gut Associated lymphoid tissue |
| How does GALT serve a peripheral function of the digestive system? | it’s the largest collection of lymphoid tissue, it serves as our defense/immune system against foreign invaders. |
| 5. Name the three pairs of salivary glands | Parotid gland, Submandibular gland, Sublingual gland |
| 6. What makes up chyme? | Watery mixture of food and secretions of liver, pancreas, and secretory epithelium |
| 7. What structure connects the mouth to the stomach? | The esophagus |
| Name the three sections of the stomach | Upper Fundus, Central Body, Lower Pylorus |
| 8. The stomach joins the small intestine at the ______. | Pyloric Sphincter |
| Name the three sections of the small intestine | Duodenum, Jejunum, Ileum |
| 9. The intestinal enzymes are aided by exocrine secretions from two accessory glandular organs. Name them | Pancreas and Liver |
| 10. What structure prevents pancreatic fluid and bile from entering the small intestine except during a meal? | Sphincter of Oddi |
| 11. Name the four layers of the gut wall (GI tract wall) | Mucosa, Submucosa, Muscularis Externa, Serosa |
| 12. Name the three parts of the mucosa | Epithelium, Lamina Propria, muscularis, mucosae |
| 13. Crumpled folds of the gut wall are called __ in the stomach and __ in the small intestine | Rugae; Plicae |
| 14. The plicae project into the lumen in small fingerlike extensions known as __. Each of these structures increase their absorptive surface with __ | Vili; microvili? Tubular invaginations |
| 15. Tubular invaginations are called __ in the stomach and __ in the intestine | gastric glands; crypts |
| 16. What is the lamina propria? | subepithelial connective tissue holds the epithelium in place |
| 17. What are Peyer's patches? | collections of lymphoid tissue in the intestine, create visible bumps in mucosa |
| 18. What part of the enteric nervous system lies in the submucosa and plays a major role in coordinating digestive function? | Meissner’s plexus |
| 19. Describe the structure of the muscularis externa | consists of two layers of smooth muscle, an inner circular layer and an outer longitudinal layer and a nerve network of the enteric nervous system (myenteric plexus), |
| The muscularis externa contains the second nerve network of the enteric nervous system called the __. | Auerbach’s plexus, myenteric plexus |
| 20. What is the structure and location of the serosa? | outer covering of the entire digestive tract, a connective tissue membrane that is a continuation of the peritoneal membrane (peritoneum) |
| What is the serosa a continuation of? | The peritoneum |
| 21. What are tonic and phasic contractions of GI smooth muscle? | tonic are sustained for minutes or hours and occur in some smooth muscle sphincters and in the anterior portion of the stomach, phasic contractions last only a few seconds occur in the posterior region of the stomach and in the small intestine |
| When a slow wave potential reaches threshold, what type of voltage-gated channels open? | calcium voltage gated channels |
| 22. What are interstitial cells of Cajal? | modified smooth muscle cells that lie between smooth muscle layers and the intrinsic nerve plexuses and act as an intermediary between the neurons and the smooth muscle |
| 23. Briefly describe migrating motor complex | a housekeeping function that sweeps food remnants and bacteria out of the upper GI tract and into the large intestine, series of contractions that start in the stomach and pass through each section towards the large intestine 90 minutes |
| Briefly describe peristaltic contraction | progressive waves of contraction that move from one section of the GI tract to the next, circular muscles contract behind a bolus to push it forward, speeds of 2-25 cm/s, occurs in esophagus, influenced by hormones, paracrines and autonomic nervous system |
| Briefly describe segmental contractions | short (1-5 cm) segments of intestine alternating contract/relax to churn the intestinal contents, mixing them and keeping them in contact with the absorptive epithelium |
| What is irritable bowel syndrome? | chronic functional disorder characterized by altered bowel habits and abdominal pain |
| 24. What is mucus comprised of, and what is its function? | glycoproteins called mucins and function to form a protective coating over the GI mucosa and to lubricate the contents of the gut |
| Give the name of the cells which secrete mucus in the stomach vs. the intestine | mucous cells in the stomach and goblet cells in the intestine |
| 25. What is the major purpose of bile? | to break down fats, fat digestion in small intestine, dispersing lipids |
| 26. What is the function of amylase in carbohydrate metabolism? | breaks long glucose polymers into smaller glucose chains and into the disaccharide maltose |
| 27. What are the roles of endopeptidases in digestion of proteins? | “proteases” attack peptide bonds in the interior of the amino acid chain and break a long peptide chain into smaller fragments, help digest protein |
| What are the roles of exopeptidases in digestion of proteins? | digest protein by releasing single amino acids from peptides by chopping them off the ends one at a time |
| 28. Because triglycerides in our diet form large clumps in aqueous chyme solution, fat digestion must be aided by __. | Bile salts, nonenzyme secretions that help make fat globules into smaller particles |
| 29. The enteric nerve plexus is referred to as the "little brain". The effect of emotional distress on GI tract function is evidence of the link between this plexus and the __. | Central nervous system |
| 30. What are long reflexes? | classical neural reflex that begin with a stimulus transmitted along a sensory neuron to the CNS, digestive reflexes integrated in the CNS that can originate with sensory receptors in the GI tract or outside the digestive system |
| What are short reflexes? | reflexes that originate within the enteric nervous system and are integrated there without outside input |
| Name the location of the myenteric plexus | located in the serosa |
| What type of stimuli starts the cephalic phase of digestion? | smelling, seeing, or thinking about food |
| 31. Give the general outcome of parasympathetic vs. sympathetic stimuli on GI functions | parasympathetic stimuli are excitatory and enhance GI functions while sympathetic stimuli usually inhibit GI function |
| 32. Although researchers have sequenced over 30 peptides which control GI function, metabolism, and eating behavior, only __ are widely accepted as hormones | some of them (about 5-8) Gastrin, CCK. Secretin, motilin, GIP, GLP-1, VIP |
| 33. GI peptides are generally divided into three groups. Name the groups, and list the peptides most readily associated with each | gastrin family (gastrin and cholecystokinin (CCK) secretin family (secretin, vasoactive intestinal peptide (VIP) and GIP gastric inhibitory peptide and glucagon-like peptide 1 (GLP-1) and outlier group (motilin) |
| 34. Why are GIP and CCK peptides of interest to researchers studying diabetes (type II) and obesity respectively? | GIP stimulates insulin release in response to flucose in the intestinal lumen and CCK binds to and activates the CCKB receptor found on parietal cells, promotes satiety, |
| 35. Name the stimuli for release of CCK | Fatty acids and some amino acids |
| Name the stimuli for release of GIP | Glucose, fatty acids, and amino acids in small intestine |
| Name the stimuli for release of Secretin | acid in small intestine |
| 36. Name a second peptide which acts similarly to CCK with regard to acting as a satiety signal | Glucagon-like peptide 1 (GLP-1), enterostatin |
| 37. Name the three phases of food processing | The Cephalic phase, the Gastric phase, and the Intestinal phase |
| 38. What makes up saliva? | water and mucus, salivary amylase, and salivary lipase? Cholrine, lysozyme, immunoglobulins |
| 39. Name the functions of amylase in the first stage of digestion | breaks starch into maltose after the enzyme is activated by Cl- in saliva |
| Name the functions of lysozyme in the first stage of digestion | antibacterial salivary enzyme disable bacteria and viruses |
| Name the functions of lingual lipase in the first stage of digestion | digestive enzyme helps break down fats and carbohydrates |
| Name the functions of immunoglobulins in the first stage of digestion | disable bacteria and viruses |
| 40. What is mastication? | mechanical digestion (chewing) of food that includes the lips, tongue and teeth |
| What is deglutition? | swallowing, a reflex action that pushes a bolus of food or liquid into the esophagus, stimulus is pressure created when the tongue pushes the bolus aginst the soft palate and the back of the mouth |
| 41. Name the three general functions of the stomach | Storage, digestion, and protection (bacteria and from acidic conditions) |
| 42. Name the roles of gastric acid (HCL) in digestion at the stomach | helps kill bacteria and other ingested microorganisms, denatures proteins by destroying their tertiary structure, breaking disulfide & H bonds, unfolding protein chains make the peptide bonds between amino acids accessible to enzymes, activates pepsin |
| Name the roles of pepsin in digestion at the stomach | Digests proteins, effective in digesting collagen and plays an important role in digesting meat |
| Name the roles of gastric lipase in digestion at the stomach | Digests fats |
| When does carbohydrate digestion cease in the stomach? | when mixing exposes the amylase to gastric acid |
| 43. Parietal cells have two important functions in the stomach. Name both | Secrete gastric acid and intrinsic factor (essential for B12 absorption) |
| Name the disease state which results from a defect in the secretion of intrinsic factor | pernicious anemia |
| What is the end result of pernicious anemia? | red blood cell synthesis “erythropoiesis”, which depends on vitamin B12, is severely diminished |
| 44. Name the secretions of chief cells | pepsin(ogen) and gastric lipase |
| Name the secretions of D cells | somatostatin |
| Name the secretions of enterochromaffin-like cells | Histamine |
| Name the secretions of G cells | Gastrin |
| Name the secretions of mucous cells | mucus and bicarbonate |
| 45. Although it is a popular myth that excess acid secretion is a common cause of peptic ulcers, the most common cause of peptic ulcers are __ | nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin and Helicobacter pylori |
| 46. How is the acidic chyme neutralized in the small intestine? | Secretin from duodenum, which inhibits acid production and gastric motility, stimulates production of pancreatic HCO3- to neutralize the acidic chime that has entered the intestine |
| Name both the facilatory and the inhibitory mechanisms of neutralizing acidic chime in the small intestine | osmoreceptors in intestine are sensitive to osmolarity of chyme, and inhibit gastric empyting if osmolarity is too high; bicarbonate secretion neurtralizes highly acidic chime coming from pancreas and is released in response to neural stimuli and secretin |
| 47. What are enterocytes? | transporting absorptive epithelial cells in the small intestine |
| What is the function of enterocytes in the small intestine? | To move ions and water into the lumen and absorb ions water and nutrients into the ECF and transport to the blood |
| 48. What is the difference between the location of pancreatic enzymes and brush border enzymes during their active phases? | brush border enzymes (peptidases, disaccharidases, and enteropeptisdase/enterokinase) are anchored to the luminal enterocyte membrane and not swept out of the small intestine as chime is propelled forward, pancreatic enzymes or in the lumen |
| 49. Brush border enteropeptidases convert inactive __ to active __ | inactive trypsinogen; active trypsin |
| 50. Sodium and bicarbonate ion are both released in response to neural stimuli and the hormone secretin. Leaky junctions between the cells, called the __, allows Na+ to move passively, and water follows | paracellular pathway |
| 51. What is the name of the liver cells which secrete bile? | hepatocytes |
| Where is the bile stored? | the gallbladder |
| How does bile reach the duodenum? | contraction of the gallbladder sends bile into the duodenum through the common bile duct |
| 52. Why is it unnecessary to ingest free amino acids in an attempt to supplement protein anabolism? | we have a lot of amino acid transport systems, already set to break down into amino acids, increases solution of gut, causing water to flow to the gut, amino acids will be excreted |
| 53. When fat digestion occurs in the small intestine, an emulsion is broken down to smaller __ with the action of pancreatic lipase and colipase | micelles |
| 54. What are chylomicrons? | large droplets of triglycerides that join cholesterol and proteins |
| How do they enter the blood stream? | they are absorbed into lacteals, the lymph vessels of the villi, |
| 55. How are bile salts recycled? | in the ileum they encounter cells that transport them back into the hepatic cell transport system |
| 56. Name the valve between the small and large intestine | ileocecal valve |
| 57. Name the seven regions of the large intestine | cecum/appendix, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anus |
| What is the main function of the large intestine? | to concentrate waste |
| 58. The discontinuous layer of longitudinal muscle in the large intestine is concentrated into three bands called the __ | tenia coli |
| 59. What are haustra? | bulging pockets that the tenia coli pull on |
| 60. The defecation reflex is aided by forced expiratory movements against a closed glottis. These forced expiratory movements are referred to as __ | valsalva maneuver |
| 61. What is the function of crypt cells in the colon? | secrete Cl- into the lumen, stem cells that divide to produce new epithelium as well as goblet cells endocrine cells and maturing colonocytes |
| 62. The WHO estimates that 4 mil ppl/year die from dehydration associated with diarrhea. Most of these cases are associated with cholera toxin from __, and enterotoxin from __. Both enhance colonic __ which is not matched by absorption | the bacteria Vibrio cholera; the bacteria Escherichia coli; Chlorine (Cl-) secretions |
| 63. __ use clathrin coated pits with membrane receptors to carry out transcytosis. Once the vesicle crosses to the extracellular compartment, macrophages and lymphocytes rid of the antigens | M cells |
| 64. What is emesis? | vomiting, the forceful expulsion of gastric and duodenal contents from the mouth, a protective reflex that removes toxic materials from the GI tract before they can be absorbed |
Created by:
alechsu