Histology of the Esophagus and Stomach Flashcards
Organization of the GI tract
mucosa
submucosa
muscularis externa
serosa/adventitia
Mucosal Layer
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
submucosal layer
- dense irregular CT w/ neurovasculature and lymphatics
- glands may also be present (esophagus/duodenum)
Muscularis Externa
two layers of smooth muscle (inner circular/outer longitudinal)
-contraction of circular =constricts lumen
-contraction of longitudinal=shortens tube
neurovascular plexuses reside between layers
Serosa/Adventitia
When digested tube is suspended by a mesentery/periotneal fold= covered by mesothelium=serosa
-no mesothelium?=adventitia
you can have either or/or both!
GI innervation
extrinsic-para and symp
intrinsic=enteric
Parasympathetics of GI
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
Sympathetics of GI
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
Intrinsic Innvervation
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)
Myenteria/Meissner
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
Esophagus
fibromuscular tube that conveys food from oropharynx to stomach
thoracic eso: adventitia
inferior to diaphragm=serosa
TWO GLANDS: cardiac/submucosal
Cardiac Esophageal glands
produce a thin layer of mucus to lubricate the epi.
reside in the lamina propria of terminal esophagus
submucosal glands
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
Gastroesophageal junction
epithelial transition from esophagus to stomach
nonkeratinized stratified squamous –> simple columnar
epi. in the stomach is glandular, with pits and glands
Sphincters of Esophagus
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)