Flashcards in Unit 6 - GIT I Deck (22)
what are the 4 principal layers of the GIT?
from outside in
what are the further subdivisions of mucosa? what are the principal functions? what do these subdivisions have?
has 3 subdivisions
-lining epithelium - changes abruptly at junctions or sphincters between major organs
-lamina propria - loose CT that resembles storma of lymphoid organs
--has blood/lymphatic vessels
--has lymphatic tissue and wandering CT (like plasma cells and eosinophils)
-muscularis mucosa - thin layer of smooth muscle that produces movement of mucosa to create ridges and valleys that facilitate absorption and secretion
for protection, absorption, and secretion
what is submucosa structure? where are there glands? what plexus is found at periphery?
dense irregular CT with blood vessels, lymphatic vessels, and nerve plexus
-in duodenum and esophagus, it has glands
-submucosa (Meissner's) plexus found at periphery (between it and circular muscle)
what is muscularis externa structure? which plexus does it have?
made of 2 thick layers of smooth muscle (inner circular along entire GIT, outer longitudinal in intestines only)
-myenteric (Auerbach's) plexus between layers
--contraction mixes and propels intestinal contents
when is it serosa or adventitia? what do these layers contain?
serosa: simple squamous epithelium (mesothelium) is present
adventitia: part of digestive tract is fixed directly to abdominal/pelvic wall
regardless, has CT, blood, and lymphatic vessels/nerves
what is the inner tongue structure? what glands are present and where? what does the dorsal surface have?
skeletal muscle arranged inside, in bundles that run in 3 planes
-mucosal and serous glands, plus adipose tissue can be found between muscle bundles
-dorsal surface has epithelium with elevations called lingual papillae
what are the 4 kinds of papillae and their structure?
filiform, fungiform, foliate, and circumvallate
-filiform lack taste buds, but are only ones with stratified squamous keratinized epithelium
-other 3 have stratified squamous epithelium with taste buds on dorsal (fungiform) or lateral (foliate/circumvallate) surfaces
what are taste buds?
onion-shaped sensory structures with 50-100 cells
how is esophagus organized in regards to the 4 layers?
-serosa VS adventitia
mucosa: stratified squamous nonkeratinizing epithelium with cardiac glands at either end (more near stomach)
submucosa: made of CT and esophageal glands proper
-upper third - skeletal muscle
-middle third - mixed skeletal and smooth
-lower third - smooth muscle
serosa is present below diaphragm, and adventitia above diaphragm
what do the cardiac glands (mucosa) VS esophageal glands proper (submucosa) secrete?
cardiac glands: nectral mucus
esophageal glands proper: viscous, slightly acidic mucus to facilitate food transport and protect epithelium
what is the UES VS LES made of?
UES: circular skeletal muscle fibers under voluntary and reflexive control?
LES: physiological sphincter of thickened circular smooth muscle fibers that is not well defined anatomically
what are the 4 regions of the stomach? how many histological regions are there?
histologically, fundus and body are together
what are rugae
temporary longitudinal folds of mucosa and submucosa that disappear when stomach is full (b/c distended)
how is stomach organized in terms of mucosa?
has gastric pits and mucosal glands
-lining epithelium is simple columnar surface mucous cells (secreting sheet)
-gastric pits are permanent invaginations into lamina propria that serve as ducts for mucosal glands
-mucosal glands are branched, tubular glands in all regions of stomach, with isthmus, neck, and base
--1-4 open into base of each pit
-lamina propria is well vascularized and cellular
-muscularis mucosa has 2 layers and sends strands up between glands
how do cardiac, gastric/fundic, and pyloric glands compare?
C: short pits and short, coiled glands
-most make mucus, a little lysozyme and HCl
G/F: medium pits and long, straight glands
-have mucous neck cells, parietal/oxyntic cells, chief cells, and enteroendocrine cells
P: very long pits and short, slightly coiled glands
-have mostly mucous cells, a few parietal cells and enteroendocrine cells
how is stomach organized in terms of:
submucosa: no permanent folds that are found in SI
muscularis externa: has extra inner layer of oblique smooth muscle in addition to usual circular and longitudinal
serosa: no adventitia
what do surface mucous cells secrete?
bicarbonate rich alkaline mucus that protects stomach's surface from acidic gastric fluid
-insoluble, cloudy, or visible mucus
what do mucus neck cells secrete? where do they occur?
-occur in small groups, or singly between parietal cells in neck of gastric glands
what do parietal/oxyntic cells secrete? where do they occur?
HCl and IF
-large eosinophilic cells found in middle and upper part of gastric gland
-can be binucleate and have intracellular canaliculus for HCl secretion
what do chief cells secrete? where do they occur?
pepsinogens and gastric lipases
-typical serous cells of columnar shape in basal half of gastric glands
what do enteroendocrine cells secrete? where do they occur?
gastrin, somatostatin, and ghrelin (act in paracrine and endocrine signaling)
-occur near base of gastric glands