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UKCD Histo GI Tract

test objective answers for GI tract

QuestionAnswer
List the 3 features of the GI mucosa that prevents internalization of aspects of the external environment. 1. mucus coat covering cell sheet; 2. semipermeable epithelial sheet; 3. junctional complex between epithelial cells.
List the 4 layers the GIT wall 1. Mucosa: epithelium, CT (lamina propria) and muscle (muscularis mucosae); 2. Submucosa: CT; 3. Muscularis externa: two layers of smooth muscle - inner circular, outer longitudinal; 4. Adventitia/Serosa (loose CT and mesotheliuum in the case of serosa).
What is the Mucosa layer composed of? epithelium (lamina propria) and muscle (muscularis mucosae)
What is the Submucosa layer composed of? CT
What is the Muscularis externa layer composed of? two layers of smooth muscle - inner circular, outer longitudinal
What is the Adventitia/Serosa layer composed of? (loose CT and mesotheliuum in the case of serosa).
What is the general function of the Mucosa layer? absorption/secretion
What is the general function of the Submocosa layer? vascular service area + holds mucosa to underlying m. externa
What is the general function of the muscularis externa layer? peristalsis
What is the general function of the Adventitia layer? adherence to surrounding structures
What is the general function of the Serosa layer? friction-free movement around surrounding structures.
What features of the Mucosa layer of the esophagus have been altered to reflect its function? stratified squamous to provide wear n’ tear epithelium
What features of the Submucosa layer of the esophagus have been altered to reflect its function? contains mucous glands to help lubricate the surface of the tube
What features of the Muscularis externa layer of the esophagus have been altered to reflect its function? has skeletal muscle in its upper 1/3 to help initiate swallowing
What features of the Adventitia layer of the esophagus have been altered to reflect its function? present as the esophagus is not in the abdomen and is held to surrounding structures of the thorax by this layer.
Does the esopohagus have a serosa or adventitia? Why? Adventitia. It is not mesenterized within the abdominal cavity but located in the posterior mediastinum of the thorax.
Why does the muscle type found in the muscularis extema vary in the esophagus? You need skeletal m. in the upper 1/3 for the initiation of swallowing. Once it gets into the tube, peristaltic contractions (non-voluntary) take it through the rest of the tubular GIT.
How do the three types of gastric glands differ? Cardiac and pyloric glands have wider, deeper gastric pits, coiled glandular portions and are composed primarily of mucus-secreting cells.
Which type of gastric gland has the most varied cell types in it? Gastric (fundic) glands have 5 cell types present in their lining.
Where do gastric glands open? Into the base of the gastric pits.
What cells compose the surface epithelium of the stomach? Surface epithelial cells that extend down into the gastric pit.
What cells are found in a gastric gland? Mucous neck cells, parietal cells chief cells and enteroendocrine cells.
What is the function (secretion) of each cell in the gastric mucosa? SEC’s secrete neutral mucin; mucous neck cells secrete acidic mucin, parietal cells secrete HCl and GIF; chief cells secrete pepsin and renin, EC’s secrete hormones.
How do active vs. inactive parietal cells differ? Active parietal cells exhibit an invagination of the apical surface membrane to form intracellular canaliculi. These serve to increase the cells apical surface area for secretion of large volumes of HCl.
hy is the basal aspect of the chief cell basophilic? The synthetic apparatus (rER) for the proteinaceous zymogen granules occupy this region of the cell.
What are zymogen granules and which gastric cell exhibits them? Proteinaceous enzyme granules. The chief cell of the gastric gland.
Which of the gastric gland cell types are not found in either cardiac or pyloric glands? No chief cells and VERY few parietal cells.
What is the function of the enteroendocrine cells? These are critical for controlling local digestive processes through hormonal release into the local blood supply.
How is the cell structurally arranged to accomodate this? The secretoryugranules are found in the basal aspects of these cells, close to the basement membrane and underlying capillaries of the lamina propria.
What are the two types of enteroendocrine cells? Type I (closed) and Type II (open).
How are the two types of enteroendocrine cells similar? They both secrete their granules basally into the underlying capillaries of the lamina propria.
How do the two types of enteroendocrine cells differ? Type I do not access the GIT lumen but respond to pressure (distention) of the GIT wall. Type II access the lumen via sensory microvilli that detect changes in the chemistry of the luminal contents.
Where do enteroendocrine cells secrete their hormonal granules? Into the blood vessels of the underlying lamina propria.
Name 3 things that increase the surface area of the small intestine for efficient absorption. Submucosal folds (plicae circularis); villi; and microvilli.
Which specialization increases surface area primarily for secretion? The presence of intestinal mucosal glands (of Lieberkuhn).
Name the four cell types found throughout the small intestine. Enterocyte; Paneth cell, enteroendocrine cell, goblet cell.
What is the function of cell in the small intestinal epithelium? Enterocytes absorb nutrients etc.; Paneth cells secret lyzozyme that digests bacterial cell walls; enteroendocrine cells secrete hormones to control local digestive activities; and goblet cells secrete mucin.
Which cells of the intestinal epithelium are found in the gland? on the villus? Paneth cells are only in the base of the glands, the others can be found in the gland or on the villus (although enterocyte predominate on the villus).
Which of the intestinal cells are not found within the epithelial lining of the colon? Paneth cells. The other 3 are all found within the lining of the colonic glands.
Which of these cells secretes zymogenic granules? The granules of Paneth cells are zymogenic in nature.
Name the 3 divisions of the small intestine - in order from the stomach distally. Duodenum, Jejunum, Ileum.
Which of the three stomach regions exhibits submucosal glands? The only region of the small intestine exhibiting submosal glands is the duodenum.
What other regions of the tubular GIT exhibits submucosal glands? Only the esophagus.
What is the function of the submucosal glands in the small intestine? They secrete large volumes of bicarbonate secretions to neutral the acidic nature of the materials entering the duodenum.
Which intestinal region exhibits Peyer's patches? The terminal ileum has the largest numbers.
What are Peyer's patches and where are they located within the intestinal wall? Masses of lymphoid nodules. The begin in the lamina propria but continued stimulation by antigen penetration causes them to get larger and push down into the submucosa - obliterating the muscularis mucosae.
What does their presence and number indicate about this region? The frequency of penetration and the high permeability of the ileum.
State the general trend, proximal to distal in the small intestine, and the functional significance for goblet cell numbers. Goblet cells, b/c you need more lubrication as the chyme begins to get thicker/loose moisture
State the general trend, proximal to distal in the small intestine, and the functional significance for lymphoid tissue. lymphoid tissue get more numerous proximal to distal in the GIT, b/c the intestinal epithelium gets more permeable
State the general trend, proximal to distal in the small intestine, and the functional significance for villous height. Villous hieght tends to become shorter and stouter in the distal regions, to withstand shearing forces.
What are the divisions of the large intestine? Cecum, appendix, ascending colon, transverse colon, descending colon, sigmoid colon and rectum
What is the function of the colon? Storage and water/mineral resorption.
What is a taeniae coli? One of 3 longitudinal bands of smooth muscle that replace the coat of outer smooth muscle in the colon.
What regions of the large intestine don't exhibit taeniae? The appendix and rectum.
What is a haustral compartment and how are they formed? A sac-shaped compartment along the length of the colon formed by the gathering of the colonic tube by the shorter taenia coli.
What is the function of these haustral compartments? Slow down passage of feces through colon so water resorption can occur.
Does the colon exhibit villi? If not why not? No villi. Due to the shearing nature of the solidfying feces.
What are the identifying characteristics of the appendix in cross section? No villi, complete ring of lymhpoid nodules in the lamina propria/submucosa and two complete layers of smooth muscle in the externa.
Created by: wiechartm