Structure + Fnx Upper GI (2) Flashcards
There is sharp change from a _______epithelium to a _______epithelium dedicated to secretion at the junction of the esophagus and stomach.
stratified squamous
simple columnar
Although there are no anatomical sphincters in the esophagus, there are two physiological
sphincters:
— pharyngoesophageal sphincter prevents reflux from esophagus into the pharynx
— gastroesophageal sphincter prevents reflux from the stomach into the esophagus
The stomach is a _______ between the intestine and
esophagus where food undergoes mechanical and
chemical digestion to form_____.
dilated sac
chyme
Mucosa and submucosa are arranged as prominent folds
called______ in the empty stomach;
holds ~ _____ by distending
rugae
1.5 liters
Churning food in gastric juice which includes:
hydrochloric acid and digestive enzymes including pepsin, rennin, and gastric lipase
_____- small area at gastroesophageal junction
______- upper left to cardia; secrete acid and enzymes
cardia
fundus
- central area of stomach; secrete acid and enzymes
_____- constricted region at base; regulates release of
chyme into duodenum (pyloric sphincter); secretes
gastrin
body (corpus)
pyloris
Epithelium in stomach mucosa
Epithelium: Simple columnar epithelium
The epithelial cells lining the lumen generate a thick mucous (visible mucous) covering that functions to:
traps bicarbonate ions (alkaline) and protects the mucosa from the low pH in the stomach; soluble mucous acts as a lubricant.
Stomach mucosa invaginates into the lamina propria forming
gastric pits (GP)
secrete histamine in response to the vagus nerve to increase acid secretion
Enterochromaffin-type cells
Muscularis mucosae (MM): smooth muscle; gastric glands extend to MM influences
gastric gland outward flow
Thick layer of dense connective tissue
Numerous wandering cells including
lymphocytes, eosinophils, mast cells, and
plasma cells
Stomach Submucosa (S):
Numerous wandering cells in submucosa include
lymphocytes, eosinophils, mast cells, and
plasma cells, May also have adipose cells
Muscularis Externa has what 3 layers?
(O, C, L):
Three layers of smooth muscle
circular and longitudinal always present
oblique fibers may also be present
contraction controlled by myenteric
(Auerbach’s) plexus between layers
The surface of the mucosa is pitted with indentations called
gastric pits.
Gastric glands are________ of epithelial cells. One to seven gastric glands open into each gastric pit.
tubular columns
Gastric pits are divided into 3 regions:
isthmus, neck, base
different epithelial cell types in each region
Gastric glands are made of a
simple columnar epithelium that
consist of 6 cell types
- Surface mucous/lining cells
(gastric pit) - Parietal (oxyntic) cells (isthmus,
neck, and base) - Neck mucous cells (neck and
base) - Chief (zymogenic, peptic) cells
(base) - Enteroendocrine cells (base)
6.Stem (regenerative) cells (neck)
The mucous in ________cells is
thick and dense while the mucous
secreted by ______cells is soluble
surface lining
mucous neck
Surface lining cell mucous adheres to
the mucosa and protects against
acid digestion
soluble mucous
lubricates the stomach contents to
aid digestion.
Differences in the make up of the
mucus can easily be seen in EM of
secretory granules
__________ are a group of cells that secrete
specific bioactive proteins
Enteroendocrine cells
Small ovoid or pyramidal cells between the
base of neighboring epithelial cells most easily
detected by immunostaining (
enteroendocrine cells
G cells secreate
gastrin
EC cells secreate:
serotonin
D cells have:
somatostatin
A cells secreate
enteroglucagon
ECL cells secreate
histamine
Enteroendocrine cells release products, which are stored as
granules, into the _______
Substances act either on surrounding cells in
_________fashion or are transported through
the bloodstream to act as_____molecules.
lamina propria.
paracrine
endocrine
Parietal cells can easily be identified within the
gastric glands because their cytoplasm stains heavily with
eosin
Pyramidal cells distinctive due to the presence
of an invagination of the apical surface called
the_________, which can almost
encircle the nucleus
secretory canaliculus
What cells are in the isthmus of the the gastric pit?
Parietal cells
What cells are located in the Neck of the gastric pit?
neck mucous cells
stem cells
parietal cells
What cells are located in the base of the gastric gland?
peptic cells
parietal cells
neck mucosa cells
neuroendocrine cells
In parietal cells, a dense network of microvilli extend into the
canaliculus that hugely increases the
the secretory surface area of the cell
In parietal cells, the ________is a unique
ultrastructural feature; its abundance inversely
correlates with HCl secretion.
Tubulovesicular network
Pariteal cells are rich in:
Extremely rich in mitochondria that provide
energy for HCl secretion
cell type at the base of the gastric
glands and secrete digestive
enzymes into the stomach lumen
Chief cells
Cheif cells are full of_____ located zymogen secretory
granules (ZG) containing proenzymes including
pepsinogen, rennin, and gastric lipase with a______
nucleus
apically
basal
What do chief cells have that allows them to accomplish high protein production?
rough ER and golgi
In chief cells, what controls granule release?
via hormonal and neural action via vagus nerve
Binding of the hormone______ to the receptors
on chief cells leads to the rapid exocytosis of
secretory granules.
secretin
Cells of gastric mucosa are completely renewed every ____ days adn depends on the proliferating stem cell compartment which lies in the ____
3 days
neck of gastric gland
As the stem cells divide, the daughter cells
differentiate and migrate upward
or downward to replace all types of epithelial cells.
The surface epithelium is also rapidly repaired after injury (e.g., by aspirin) by the rapid migration of epithelial cells lying deep in the protected environment of the pits in a process called
- mucosal restitution
How can we tell fundus and body of stomach apart on histology?
Can’t! they are histologically indistinguishable with straight tubular glands
Pylorus contains the same cell types as other regions, however, the glands are______ and ______ cells predominate.
branched
mucous neck
What is characteristic of the cardiac region of the stomach in regards to:
gastric pits
glands
enteroendocrine cells
Cardiac region has shallower gastric pits, and the glands are highly coiled.
There is an abundance of enteroendocrine cells.
What are the three phases of the stomach after a meal?
Cephalic phase
Brain anticipates meal – smells, visual cues
Parasympathetic signals via vagus nerve –> Acetylcholine (ACh) release – >acts on G cells –> gastrin secretion
Gastrin, ACh, and histamine –> act on parietal cells to stimulate limited HClrelease (*30% total gastric acid)
Gastric phase -
Food enters stomach –> distention –> increases G cell activity
Increased gastric juice release (*60% total gastric acid)
Onset of powerful smooth muscle contraction –> mechanical digestion
Intestinal phase -
Chyme released into duodenum
Gastric emptying slows
Distention of intestine –> gastric-inhibitory impulses by ENS = enterogastric reflex
Cholecystokinin and secretin suppress gastric activity (*10% gastric acid)
