Histology of the Esophagus and Stomach

Question 1

Organization of the GI tract

Answer 1

mucosa
submucosa
muscularis externa
serosa/adventitia

Question 2

Mucosal Layer

Answer 2

Three components!

• lining epithelium (varies segment to segment)
• underlying lamina propria (vascularized loose CT has lymphatic nodules, lymphocytes, plasma cells, macrophages)
• muscularis mucosae (this smooth m) –> controls mobility of mucosa/mucosal glands

Question 3

submucosal layer

Answer 3

• dense irregular CT w/ neurovasculature and lymphatics

- glands may also be present (esophagus/duodenum)

Question 4

Muscularis Externa

Answer 4

two layers of smooth muscle (inner circular/outer longitudinal)
-contraction of circular =constricts lumen
-contraction of longitudinal=shortens tube
neurovascular plexuses reside between layers

Question 5

Serosa/Adventitia

Answer 5

When digested tube is suspended by a mesentery/periotneal fold= covered by mesothelium=serosa
-no mesothelium?=adventitia
you can have either or/or both!

Question 6

GI innervation

Answer 6

extrinsic-para and symp

intrinsic=enteric

Question 7

Parasympathetics of GI

Answer 7

vagus nerve (until splenic fixure)
pelvic splanchnic (splenic flexure --> inferiorly
fibers in vagus and pelvic splanchnics are presynaptic
ganglion and post synaptic fibers are intramural

Question 8

Sympathetics of GI

Answer 8

branches from greater, lesser, least and lumbar splanchnics

• synapse in prevertebral ganglia (celiac, SM, aorticorenal and IM ganglia)
• postsynaptic nerves travel to organs via blood vessels on peri-arterial plexuses

Question 9

Intrinsic Innvervation

Answer 9

two plexuses of sensory and motor linked by interneurons

1) submucosal plexus of meissner-found in submucosa and is responsible for regulating secretion of glands in submucosa
2) myenteric plexus of auerbach-between inner circ and outer long. layers (lighter stained)

Question 10

Myenteria/Meissner

Answer 10

responsive to local stimuli and input from ANS
regulate and control:
1)peristaltic contractions of muscularis externa and movements of muscularis mucosae
2) secretory activities of the mucosal and submucosal glands

Question 11

Esophagus

Answer 11

fibromuscular tube that conveys food from oropharynx to stomach
thoracic eso: adventitia
inferior to diaphragm=serosa
TWO GLANDS: cardiac/submucosal

Question 12

Cardiac Esophageal glands

Answer 12

produce a thin layer of mucus to lubricate the epi.

reside in the lamina propria of terminal esophagus

Question 13

submucosal glands

Answer 13

produce a thin layer of mucus to lubricate the epi.

consists of small lobules with mucous and serous cell types, drained by a single duct

Question 14

Gastroesophageal junction

Answer 14

epithelial transition from esophagus to stomach
nonkeratinized stratified squamous –> simple columnar
epi. in the stomach is glandular, with pits and glands

Question 15

Sphincters of Esophagus

Answer 15

Upper esophageal sphincter: anatomical, swallowing reflex
lower esophageal sphincter: functional, prevents reflex of gastric contents (designed to be closed down so acid components dont move superiorly)

Question 16

Gastroesophageal reflux disease (GERD)

Answer 16

causes chronic inflammation, ulceration, and difficulty swallowing (dysphagia) due to reflex of gastric contents
-loosening of sphincter causes backflow of acid

Question 17

Barret’s Esophagus

Answer 17

chronic
nonkeratinized stratified squamous in transition zone –> becomes columnar mucus-secreting/glandular, barret’s esophagus/metaplasia

Question 18

Regions of stomach

Answer 18

cardia: 2-3 cm near esophageal opening
fundus: projects to the left of the cardia
body: extensive central region
pyloric antrum: ends at gastroduodenal orifice

Question 19

Orad area

Answer 19

fundus and upper part of the body, relaxes during swallowing

LES area

Question 20

caudad area

Answer 20

lower portion of the body and the antrum, participates in the regulation of gastric emptying

Question 21

Rugae

Answer 21

gastric mucosal folds/ridges that mix food and break it down. IT helps to increase friction and break down internal food components.
in mucosa/submucosa
-covered by gastric pits

Question 22

Fundic (gastric) glands

Answer 22

present throughout gastric mucosa except for areas occupied by cardiac and pyloric glands
-simple branched tubular glands (extend from bottom of gastric pits –> muscularis muscosae) (several open into a single gastric pit)

Question 23

Gastric gland: isthmus

Answer 23

between gastric pit and gland below
site of stem cell niche
-dividing and undifferentiated cells (connector region of functional component of gland to gastric pit)

Question 24

gastric gland: neck segment

Answer 24

narrow, relatively long region
mucous neck cells (secrete mucus)
parietal cells
enteroendocrine cells

Question 25

gastric gland: fundic segment

Answer 25

shorter and wider base -chief cells -enteroendocrine cells some parietal cells

Question 26

Mucous cells

Answer 26

a mucus layer, containing 95% water, 5% mucin - forms an insoluble gel that attaches to surface of gastric mucosa - 100 um thick coating that neutralizes the microenvironment to an alkaline pH

Question 27

surface mucous cells

Answer 27

line the pits (insoluble) have apical granules containing mucins. has abundant mito, and carbonic anhydrase contribute to the formation of bicarbonate ions --> increase pH

Question 28

mucous neck cells

Answer 28

located in the neck, at the opening of the gastric gland into the pit

Question 29

Chief cells

Answer 29

basal region of the cytoplasms contains extensive RER | numerous zymogen granules are located in apical region. release contents via exocytosis

Question 30

Pepsinogen

Answer 30

proenzyme stored in the zymogen granules - released into the lumen of the gland - converted to pepsin by acid enviroment - proteolytic enzyme that digests most proteins - exocytosis of pepsinogen is rapid and simulated by feeding

Question 31

Enteroendocrine cells

Answer 31

have two types of cells: closed cells and open cells | -all levels of fundic glands, but more prevalent in the base

Question 32

Closed cells of enteroendocrine cells

Answer 32

small cells that rest on the basal lamina and do not always reach the lumen -indirectly regulated by luminal content via neural and paracrine mechanisms

Question 33

Open cells of enteroendocrine cells

Answer 33

have a thin cytoplasmic extension w/ microvilli and are exposed to gland lumen -chemoreceptors that sample luminal contents and release hormones

Question 34

Gastrin

Answer 34

produced by G cells in pyloric antrum - stimulates production of HCL by parietal cells - released in stomach, duodenum, jejunum

Question 35

somatostatin

Answer 35

produced by D cells - inhibits gastrin action - throughout entire GI tract

Question 36

ghrelin

Answer 36

produced in gastric fundus -binds its receptor in pituitary and stimulates GH secretion -Ghrelin plasma levels increase during fasting --> triggers hunger released in fundus

Question 37

Cardiac Glands of Stomach

Answer 37

narrow region of stomach (the 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 Hallmark: appear circular and oblique in sections

Question 38

Pyloric Glands of stomach

Answer 38

branched, coiled, tubular glands between fundus and pylorus -GLANDS EMPTY INTO PITS THAT OCCUPY HALF OF MUCOSA -lined by mucus-secreting cells (resemble surface mucous cells) -large and pale secretory mucus occasional enteroendocrine cells and parietal cells are present; GALT in lamina propria