Histology of the esophagus and the stomach

Question 1

what are the four main layers of the GI tract?

Answer 1

from lumen to superficial:

1) The mucosa
2) the submucosa
3) the muscularis externa
4) the serosa/adventitia

Question 2

Components of the general Mucosal layer

Answer 2

Has three components:
-lining epithelium (varies segment to segment)

-underlying lamina propria (vascularized loose CT) lymphatic nodules, lymphocytes, plasma cells, and macrophages are present here

-A thin layer of smooth muscle, the muscularis mucosae
which controls the mobility of the mucosa glands

Question 3

Components of the general submucosal layer

Answer 3

Submucosal layer is composed of

• consists of a dense irregular CT with neurovascular and lymphatics
• glands may also be present in the esophagus and duodenum

Question 4

Components of the general Muscularis externa layer

Answer 4

Two layers of smooth muscle, inner circular layer and a outer longitudinal layer

contraction of circular will constrict lumen

contraction of the longitudinal layer will shorten the lumen

Neurovascular plexuses reside between layers

Question 5

Components of the general Serosa/Adventitia layer

Answer 5

When digestive tube is suspended by a mesentary/peritoneal fold, the adventita is covered by mesothelium forming the serosa layer (peritoneum)

those without mesothelium covering have an adventita (retroperitoneal)

organs may have an adventita and or serosa depending on the location

Question 6

what are the 4 basic mucosal types, where they are found and their function in the GI tract

Answer 6

Nonkeratinized stratified squamous cells:

• found in oral cavity, pharynx, and anal canal
• protective

Simple columnar epithelium:

• mucosa arranged as villi with crypts, glands and maybe present in small intestine
• absorptive

Simple columnar epithelium

• mucosa packed with glands
• found in stomach
• secretory

Simple columnar epithelium

• mucosa arranged into closely packed glands with extensive goblet cells
• found in large intestine
• Absorptive and protective

Question 7

what are the two plexuses found in the epithelium and their function

Answer 7

Part of the intrinsic (enteric) innervation

1) submucosal plexus of meissner
2) myenteric plexus of auerbach
- between the inner circular and outer longitudinal layers

Responsive to local stimuli and input from the ANS regulate control:

• peristalic contractions of muscularis externa and movements of the muscularis mucosae
• secretory activities of the mucosal and submucosal glands

Question 8

does the esophagus have serosa or adventita?

Answer 8

both:

Thoracic esophagus is adventita because it is retroperitoneal

inferior to the diaphram is serosa because it is peritoneal

Question 9

Characteristics of the Mucosa, Submucosa and muscularis layers of the esophagus

Answer 9

Mucosa:

• nonkeratinized stratified squamous overlying a lamina propria
• numerous folds
• muscularis mucosae only found in lower segment

submucosa:

• network of collagen, elastic fibers and small blood vessels
• Submucosal venous plexuses drain both the systemic and portal venous systems
• increase in pressure can cause esophageal varices

Muscularis:

• inner circular and outer longitudinal layers have segment dependent variations
• upper third = skeletal muscle
• middle third = skeletal and smooth muscle
• lower third = smooth muscle

Question 10

what are two glands found in the esophagus and their function

Answer 10

Mucosal and submucosal produce a thin layer of mucus to lubricate the epithelium

• Cardiac esophageal glands: reside in the lamina propria of termial esophagus and help protect from acids from the stomach
• Submucosal glands: consist of small lobules with mucous and serous cell types drained by a single duct

Question 11

what are the sphincters of the esophagus?

Answer 11

Upper esophageal sphincter (UES)
-anatomical. swallowing reflex

Lower esophageal sphincter (LES)
-functional, prevents reflux of gastric contents

Question 12

what is GERD and Barretts esophagus

Answer 12

Gastroesophageal reflux disease:
-causes chronic inflammation, ulceration and difficult in swallowing (dysphagia) due to reflux of gastric contents

If chronic, nonkeratinized stratified squamous in transition to columnar mucus secreting glandular that is similar to the stomach cell type
-this dysplasia is called barretts esophagus

Question 13

What is the gastroesophageal junction?

Answer 13

Epithelial transition from the esophagus to the stomach

• nonkeratinized stratified squamous to simple columnar
• epithelium in the stomach is glandular with pits and glands

Question 14

what are the 4 regions and 2 motillity areas of the stomach

Answer 14

Four regions:

• Cardia: near the esophageal opening
• fundus, projects to the left of the cardia
• body, an extensive central region
• Pyloric antrum: ends at the gastroduodenal orifice

Based on motillity characteristics:

• Orad area = fundus, and upper part of the body relaxes during swallowing
• caudad area: lower portion of the body and the antrum that participates in the regulation of gastric emptying

Question 15

what are rugae?

Answer 15

Gastric mucosal folds that are covered by gastric pits

this is also covered by a gastric mucosal barrier that protects the mucosal surface

Question 16

Mucosa, submucosa, muscularis, and serosa of the stomach

Answer 16

Mucosa:

• simple columnar epithelium
• lamina proprioa contains cardiac, gastric, and pyloric glands
• reticular and collagen fibers predominate
• muscularis mucosae facillitates release of gastric gland secretions

submucosa:

• dense irregular CT w collagen and elastic fibers
• arterioles, venous plexuses and lymphatics
• meissners plexus (submucosal plexus)

Muscularis externa

• three layers of smoot muscle, oblique, circular, and longitudingal
• circular muscle layer thickens in pyloric region forming the pyloric sphincter

Serosa:
-loose CT and blood vessels

Question 17

what are the fundic glands and what make up its components?

Answer 17

Simple branched tubular glands that are present throughout the gastric mucosa
-extend from the bottom of the gastric pit to the muscularis mucosae

Gastric pit:
-invaginations of the mucosal surface

Isthmus/neck:

• narrow region between gastric pit and gastric gland
• contain stem cells

Gastric gland:
-shorter and wider base

Question 18

what are the characteristics of the 2 mucous cells? what do they secrete

Answer 18

Surface mucous cells that line the lumen and the gastric pit

Mucous neck cells that are located in the neck in singles and or clusters

• round nuclei and apical secretory granules
• also down into the gastric gland

these secrete a mucus layer that contains 95% water and 5% mucin

• forms an insoluble gel that attaches to the surface of the gastric mucosa
• thick coating that neutralizes the micronenvironment to an alkaline pH

Question 19

what are chief cells and their function

Answer 19

Predominately in inferior regions of the gastric glands
-abundant RER and apical secretory zymogen granules

produce Pepsinogen, the proenzyme stored in secretory granules

• released and converted to pepsin by acidic environment
• proteolytic enzyme that digests most proteins
• exocytosis of pepsinogen is rapid and stimulated by feeding

also produce gastric lipase to digest lipids

Question 20

what are Parietal cells and their function

Answer 20

Predominate near neck and upper segment of the gastric gland

Produce HCl acid and intrinsic factor which is a glycoproptein that binds vitamin B12

Large cells usually round or pyramidal shaped

• one or two central round nuclei
• cytoplasm is esentially eosinophillic due high amounts of mitochondria

contain an intracellular canaliculus
-large surface area produced by thousands of microvili

Question 21

what are enteroendocrine cells and their function?

Answer 21

Scattered epithelial cells in gastric mucosa with endocrine/paracrine functions

secrete a range of products physiological critical for digestive function

important for releasing hormones and are found throughout the GI tract

Question 22

What are cardiac glands and their function?

Answer 22

Found in the narrow region of the stomach (cardia) that surrounds the esophageal orifice

glands are tubular, coiled and somewhat branched

opening is continuous with the gastric pits

lined with mucus secreting cells

appear circular and oblique in sections

Question 23

what are pyloric glands and what are their functions

Answer 23

Branched coiled tubular glands between fundus and pylorus

glands empty into pits that occupy half of mucosa

lined by mucus secreting cells
-large pale secretory mucus

Occasional enteroendocrine cells and parietal cells are present
lymphoid nodules can be seen in the lamina propria (GALT)