Histology of GI tract organs and peritoneum

four tunics

1. mucosa (innermost with direct contact to foodstuffs, chyme, and feces)

2. submucosa

3. muscularis (muscularis externa)

4. adventitia or serosa (outermost layer covering organ)

mucosa

• inntermost layer

• epithelial tissue is

  • stratified (protection)- mouth, esophagus, anal canal

  • columnar- stomach and intestine

• lamina propria- loose CT layer

• muscularis mucosae- tensing of muscle makes ridges and impacts surface area of epithelium

submucosa

• loose areolar CT and dense irregular CT

• blood vessels and nerves

• glands

• MALT (Mucosa-Associated Lymphoid Tissue)

submucosal nerve plexus

within the submucosa throughout digestive tract; controls secretion

muscularis (aka muscularis externa)

• two layers of smooth msucle characterized by how muscle fibers run

  • inner circular layer

  • outer longitudinal layer

• muscles in this layer propel food along and prevent improper movement of food

  • peristalsis

  • sphincters

• submucosal plexus

myenteric plexus

between circular and longitudinal layer of muscle throughout digestive tract; controls motility

serosa

• thin layer of areolar CT and simple squamous epithelium

• covering of digestive organs below esophagus

• intraperitoneal

adventitia

• dense irregular CT anchoring organs in plase

• retroperitoneal

• located in esophagus and duodenum

peritoneum

serous cavity housing the abdominal organs; serous membrane

• parietal layer is outermost layer, folds inward

• visceral layers attaches to organs directly

• serous fluid between layers reduces friction during movement

abdominal organs move- can’t be firmly anchored to an area

• anchored by mesenteries

mesenteries

thin sheets of CT that anchors and suspends organs; useful for blood vessel and nerve passages; lymphatic tissue for immune responses

• folds of the parietal peritoneum

• prevents tangling/twisting of organs

• greater omentum, lesser omentum, transverse mesocolon

greater omentum

• suspended from stomach and hangs down anterior abdominal region; stores fat

• stores fat; immune component

lesser omentum

• suspended between liver and lesser curvature of stomach

• passageway for arteries, veins, lymphatics, etc.

transverse mesocolon

• between transverse colon and posterior abdominal wall

• secretes/absorbs serous fluid in peritoneal cavity

intraperitoneal

organs enclosed by mesentery

retroperitoneal

organs only covered on anterior side

adventitia organs

• esophagus

• duodenum

• ascending colon

• descending colon

• rectum and anal canal

serosa organs

• stomach

• jejunum

• ileum

• cecum and appendix

• transverse colon

• sigmoid colon