Histology of the Esophagus and Stomach Flashcards
What are the layers of the GI tract (lumen to superficial)?
Mucosa
Submucosa
Muscularis externa
Serosa/adventitia
What are the 3 components of the mucosa?
lining epithelium
lamina propria of vascularized loose CT that contains lymph structures plasma cells and macrophages
thin layer of muscularis mucosae which is only involved in movement of mucosa
What composes submucosa? What parts of GI tract have glands in this layer?
dense irregular CT with neurovascular and lymphatics
esophagus and duodenum
What are the 2 layers of the muscularis and what is between them?
inner circular and outer longitudinal, contraction of circular constricts lumen and contraction of longitudinal shortens tube
neurovascular plexuses
What constitutes something as having a serosa layer?
digestive tube suspended in mesentery/peritoneal fold its covered by mesothelium
no mesothelium covering= adventitia
What cells make protective mucosa? Where is it found?
non-keratinized stratified squamous
oral cavity, pharynx, and anal cavity
What cells make absorptive mucosa? Where is it found?
simple columnar epithelium mucosa arranged as villi with crypts
glands present in SI, absorb H2O as harden waste
What cells make secretory mucosa? Where is it found?
simple columnar epithelium, mucosa packed with glands,
stomach
What cells make absorptive/protective mucosa? Where is it found?
simple columnar epithelium, mucosa arranged into closely pack glands (LI), extensive goblet cells
large intestine
What are the 2 plexuses that supply intrinsic/enteric innervation?
Submucosal plexus of Meissner
Myenteric plexus of Auerbach between inner circular and out longitudinal layers
What does the enteric innervation control?
Peristaltic contractions of muscularis externa and movements of muscularis mucosae
Secretory activities of the mucosal and submucosal glands
Does the thoracic esophagus have adventitia or serosa?
adventitia but inferior to diaphragm it’s serosa
Where are cardia esophageal glands found?
in lamina propria of terminal esophagus
What are submucosal glands?
small lobules with mucous and serous cell types drained by a single duct
What kind of mucosa is found in the esophagus?
nonkeratinized stratified squamous overlying a lamina propria, numerous folds, muscularis mucosae only in lower segment
Describe the submucosa of the esophagus
network of collagen and elastic fibers, submucosal venous plexuses drain into both systemic and portal venous systems, increase in pressure can cause esophageal varices –> dilation of submucosal venous sinuses
What kind of muscles is found in the upper 1/3, middle 1/3, and lower 1/3 of the esophagus?
Upper third= skeletal (striated)
Middle third= skeletal and smooth
Lower third= smooth muscle
What 2 sphincters are found in the esophagus? Are they functional or anatomical?
upper esophageal= anatomical and swallowing reflex
lower= functional prevents reflux of gastric contents
What is GERD? What happens when it becomes chronic?
Chronic inflammation, ulceration, and difficulty in swallowing due to reflux of gastric contents
Non-keratinized stratified squamous in transition zone becomes columnar mucus-secreting/glandular Barrett’s esophagus/metaplasia
What is the gastroesophageal junction?
epithelial transition from esophagus to stomach aka non-keratinized stratified squamous to simple columnar, epithelium in stomach is glandular with pits and glands
What are the regions of the stomach?
cardia near esophageal opening
fundus projects to left of cardia
body
pyloric antrum that ends at gastroduodenal orifice
What covers gastric mucosal folds (rugae)? How are they protected?
gastric pits
gastric mucosal barrier
What kind of mucosa is found in the stomach? What fibers predominate?
simple columnar epithelium
collagen and reticular
What glands are found in the lamina propria of the mucosa of the stomach?
cardiac, gastric, and pyloric glands
muscularis mucosae facilitates release of gastric gland secretions
Describe the submucosa of the stomach
dense irregular CT with collagen and elastic fibers, arterioles venous plexuses and lymphatics, Meissner’s plexus
What are the 3 layers of the muscularis of the stomach?
oblique, circular, and longitudinal
circular muscle layer thickens in pyloric region forming sphincter
Does the stomach have serosa or adventitia? What does it contain?
serosa
loose connective tissue and blood vessels
What are fundic gastric glands? What are its parts?
simple branched tubular glands, extend from bottom of pits to muscularis mucosae
Gastric Pit= invagination of mucosal surface
Isthmus/neck= narrow region btwn pit and gland
Gastric gland= shorter and wider base
Where are surface mucous cells found?
lining the lumen and gastric pits
What is the job of the mucus layer?
forms insoluble gel that attaches to surface of gastric mucosa
thick coating neutralizes micro-environment to alkaline pH
Where are chief cells predominately found? What do they release and what is its role?
Inferior regions of gastric glands
Pepsinogen which is converted to pepsin by acidic environment, proteolytic enzyme that digest most proteins, exocytosis of pepsinogen rapid and stimulated by feeding
Where are parietal cells found? What do they produce?
neck and upper segment of gastric
HCl and intrinsic factor (B12 absorption)
What happens when parietal cells are active?
There is a deep invagination of apical plasma membrane= intracellular canaliculus –> increase SA
What are enteroendocrine cells?
scattered epithelial cells in gastric mucus with endo/paracrine functions, secrete wide range of products for digestion
What is the structure of cardiac glands?
Narrow region of stomach that surrounds esophageal orifice
Tubular, coiled, and somewhat branched
Opening continuous with gastric pits
Lined with mucus secreting cells
What is the structure of pyloric glands?
Branched coiled tubular glands between fundus and pylorus
Glands empty into pits that occupy half of mucosa
Lined by mucus-secreting cells, large and pale
Occasional enteroendocrine and parietal cells present, lymphoid nodules seen in lamina propria= GALT
