Upper GI Structure/Function Flashcards
What is semi-fluid of partially digested food in the stomach called?
chyme
Where is voluntary muscle located in the GI tract?
upper 1/3 of esophagus
What are the 4 general layers of the GI tract? (luminal inward)
Mucosa
Submucosa
Muscularis Externa
Adventitia/Serosa
What are the thee layers of the mucosa?
Epithelium
Lamina Propria
Muscularis mucosae
What is the role of the mucosal epithelium? (general)
mucosal function
What is the role of the lamina propria? (general)
supports epithelium, contains lymphocytes and plasma cells
What is the role of the muscularis mucosae? (general)
local movements and folding of mucosa
houses capillaries
Waht is submucosa? What is it’s function?
layer of loose collagenous and adipose tissue
supports the mucosa
contains large blood vessels and lymphatic vessels
Where does the submucosa contain mucous secreting glads?
esophagus and duodenum
What part of the enteric nervous system is in the submucoa? What type of innervation is this?
submucosal (meissner’s) plexus
parasympathetic ganglia
Which layer of the muscularis externia is internal? external?
internal: circular
outer: longitudinal
What is the role of the muscularis externa?
peristalsis
What type of muscle is muscularis externa?
smooth
What part of the enteric nervous system is in the muscularis externa? what does it control?
myenteric (auerbach’s) plexus
control’s peristalsis
What is the adventitia/serosa?
outermost covering of the GI tract
Define adventitia
loose connective tissue layer surrounding he GI tract wtihin he peritoneal cavity
Define serosa
simple squamous epithelium (mesothelium) along with conntective tissue that covers the GI tract within the peritoneal cavity
(epithelium secretes serous fluid to lubricate)
What neurotransmitters does the enteric nervous system use?
Ach
NE
serotonin
What does the submucosal/meissner’s plexus do?
controls mucosal movement, secretory activity and blood flow
What does the myenteric/auerbach’s plexus do?
controls peristaltic gut movements
What type of mucosa is in the upper gi tract and anus? function?
stratified squamous, non-keratinized, contains langerhans cells
protective
What type of mucoas is found in the stomach? function?
simple columnar epithelium thick mucous, traps bicarbonate ions gastric pits secretory contains abundance of tubular glands
What type of mucosa is found in the SI? function
absorptive
mucosa is folded into villi to maximize surface area
What type of mucosa is found in the LI? function?
absorptive/protective
produces mucin and absorbs water
What secretes mucous to help propel food down the esophagus?
esophageal cardiac glands
Where are esophageal glands located? function?
submucosa
arranged in acini
contain mucous cells and serous cells
secrete pepsinogen & lysozyme
Where is the adventitia/serosa border of teh esphoagus?
the diaphragm
What cell types make up the GEJ
stratified squamous to simple columnar
What are the 2 physiological sphincters of the esophagus
pharyngoespophageal-prevents reflux from esophaus to pharynx
gastroesophageal-prevents reflux from stomach to esophagus
What are the 4 anatomical regions of the stomach?
cardia
fundus
body
pyloris
What makes up gastric juice?
HCl, pepsin, rennin, gastric lipase
Describe the lamina propria of the stomach
contains gastric glands
enterochromaffin type cells
What do enterochromaffin-type cells do?
secrete histamine in response to vagus nerve to increase acid secretion
How many layers of muscle are in the stomach?
3
circular, oblique, longitudinal
What are gastric pits?
pitted surface of mucosa
What are gastric glands?
tupular columns of epithelial cells
3 regions: isthmus, neck, base
What are the 6 cell typesof simple columnar epithelium in gastric glands?
- surface mucous/lining cells (gastric pit)
- parietal cells (isthmus, neck & base)
- neck mucous cells (neck & base)
- Chief (peptic) cells (base)
- Enteroendocrine cells (base)
- Stem/regenerative cells (neck)
What type of mucous is secreted by surface lining cells? mucous neck cells?
surface lining cells-thick & dense, adheres to mucosa and protects against acid
mucous neck cells-soluble, lubes stomach to aid digestion
What substances do enteroendocrine cells secrete?
usually a single bioactive agent G-cells: gastrin EC cells: serotonin D cells: somatostatin A cells: enteroglucagon ECL cells: histamine can act paracrine or endocrine
What do parietal cells secrete? features of parietal cells?
HCl Intrinsic factor secretory cnaliculous-makes pyramidal, microvilli extend into Tubulovesicular network lots of mitochondria
What do chief cells secrete? features of chief cells?
pepsinogen, rennin, gastric lipase (from zymogen secretory granules)
lots of RER & golgi
base of gastric glands
binding to secretin leads to rapid exocytosis of secretory granules
vagus nerve stimulates enzyme release
Describe the regenerative stem cells of the gastric glands
found in neck of gastric gland
mitotic figures
daughter cells differentiate and migrate
What is mucosal restitution?
surface epithelium repair after injury by rapid migration of epithelial cells lying deep in the protected enrionment of the pits
What type of glands are found in the fundus/body?
straight tubular
What types of glands are found in the pylorus?
branched, mucous neck cells predominate
What type of glands are found in the cardiac region?
shallower gastric pits, highly coiled
What is the cephalic phase?
brain anticipates meal
parasympathetic signals vagus–>gastrin secretion
30% gastric acid released
What is the gastric phase?
food enters stomach->distention->increased G cell activity
60% total gastric acid released
What is the intestinal phase?
Chyme released into duodenum
enterogastric relfex
10% gastric acid released
What is the enterogastric reflex?
distention of the intestine–>gastric-inhibitory impulses by ENS
