Structure + Fnx Upper GI (2) Flashcards by Meghan May

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

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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

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The stomach is a _______ between the intestine and
esophagus where food undergoes mechanical and
chemical digestion to form_____.

dilated sac

chyme

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Mucosa and submucosa are arranged as prominent folds
called______ in the empty stomach;

holds ~ _____ by distending

rugae

1.5 liters

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Churning food in gastric juice which includes:

hydrochloric acid and digestive enzymes including pepsin, rennin, and gastric lipase

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_____- small area at gastroesophageal junction

______- upper left to cardia; secrete acid and enzymes

cardia

fundus

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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

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Epithelium in stomach mucosa

Epithelium: Simple columnar epithelium

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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.

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Stomach mucosa invaginates into the lamina propria forming

gastric pits (GP)

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secrete histamine in response to the vagus nerve to increase acid secretion

Enterochromaffin-type cells

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Muscularis mucosae (MM): smooth muscle; gastric glands extend to MM influences

gastric gland outward flow

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Thick layer of dense connective tissue
Numerous wandering cells including
lymphocytes, eosinophils, mast cells, and
plasma cells

Stomach Submucosa (S):

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Numerous wandering cells in submucosa include

lymphocytes, eosinophils, mast cells, and
plasma cells, May also have adipose cells

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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

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The surface of the mucosa is pitted with indentations called

gastric pits.

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Gastric glands are________ of epithelial cells. One to seven gastric glands open into each gastric pit.

tubular columns

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Gastric pits are divided into 3 regions:

isthmus, neck, base
different epithelial cell types in each region

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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)

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The mucous in ________cells is
thick and dense while the mucous
secreted by ______cells is soluble

surface lining

mucous neck

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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)