Lecture 31 - GI Flashcards
mucosa
innermost
- epithelial lining cells
- lamina propria
- muscularis mucosae
submucosa
loose tissue; contains blood vessels, nerves, lymphatics
muscularis propria (muscle proper)
inner circular muscle
outer longitudinal muscle
(Squeeze and propel)
serosa
thin outer lining
layers of GI
mucosa
submucosa
muscularis propria
serosa
layer of bowel
MUCOSA: lumen to epithelium, lamina propria, muscularis mucosa
SubMucosa: Clear space
Circular around: inner circulars, longitudinally arranged fiber
Serosa then adventisial
two main plexi in gi tract
submucosal plexus
myenteric plexus
GI tract NS innervation
CNS and ENS (enteric nervous system, unique to gut)
ENS nerves arise where
in GI tract, connect to CNS but also have intrinsic set of nerves
“second brain”
ENS – colloquial
PS input to the gut is at what level
craniosacral
craniosacral nerves do what
leave CNS and dont interact with another neuron until they reach the enteric system
sympathetic NS nerves arise where
thoracolumbar
thoracolumbar nerves do what
synapse in prevertebral ganglia, THEN they go to the gut and GI tract
does enteric need CNS
no, it can function without.
EX: quadraplegic people still have functional GI tract
gi tract innervation with different plexi
myenteric plexus is well represented throughout, submucosal you dont see until small and large intestine
submucosal plexus really important for what
digestion
esophagus function
convey food from mouth to stomach
key structural features of esophagus
1) epithelial cells are stratified squamous (non keratinized)
2) varying muscularis propria
3) no serosa
variance of muscularis propria in esophagus
upper 1/3 skeletal
middle 1/3 skeletal and smooth
lower 1/3 smooth
esophagus located where
posterior mediastinum
where does vagus travel
alongside esophagus and wraps around stomach
histologically, what changes the most from one part of gi to another
the epithelium
lower esophageal sphincter is not really a
sphincter - really a high pressure zone to keep acid from going into esophagus
function of stomach
begin digestion mechanically and chemically converting food into chyme
structural features of stomach
1) epithelium: glands with specialized cells
2) muscularis propria: 3 layers (oblique layer)
specialized cells in epithelium of stomach stomach
parietal cells (secrete acid; intrinsic factor) chief cells (secrete pepsinogen) G cells (secrete hormone gastrin) mucous cells (protect, lubricate mucosa)
stomach can be divided into what two parts
fundus and body secretion reservoir and then distal antrum (mixing and grinding)
where is acid made
promixal part of stomach
where is gastrin made
antrum
which comes first, acid or gastrin
first acid, then gastrin
glands in stomach
fundic, pyloric, cardias
fundic glands
- fundus and body of stomach
- long, branched glands with mucous, parietal, chief and endocrine cells
pyloric glands
- antrum and pyloric areas
- long, branched glands consisting almost exclusively of mucous cells and endocrine cells (G cells)
cardiac glands
- proximal stomach, just past the GE junction.
- short, branched tubular glands consisting mainly of mucous cells
- not very functional
common epithelial aspects of stomach
have pits in glands that is lined with mucous producing cells to protect the stomach from acid
what distinguishes the different glands
the cells BELOW the pits!
gastric fundic gland cell types from top to bottom
mucous, parietal (acid), ECL cell (histamine), chief cells (pepsinogen)
gastric epithelial cells
foveolar mucous neck parietal cells chief cells endocrine stem
foveolar cells
located at surface; mucous cells with faint, pink cytoplasm; rectangular shape
mucous neck cell
located at base of gastric pits; pale mucous vacuoles
parietal cells
located lower in fundic gland; eosinophilc cytoplasm with central nucleus (“fried egg” appearance); eosinophilic cytoplasm (mitochondria); invaginations of the plasma membrane
LOVES THESE
chief cells
located near parietal cells; pyramidal cells with basophilic cytoplasm (numerous ribosomes); zymogen granules in apical cytoplasm
Endocrine cells
seen with special immunohistochemical stains; eosinophilic secretory granules.
Ex: ECL
stem cells
Located in mucous neck region
what surface is proton pump on
apical
how do we fit more proton pumps in the cells
by making folds
production of acid by parietal stimulated by
acetylcholine, histamine, and gastrin
upper endoscopy takes you until
end of duodenum
colonoscopy takes you to
upper colon
