Week 9: Microscopic Anatomy of the GI System

mucosa, submucosa, muscularis externa, serosa

four layers of the GI Wall

mucosa

comprises the innermost layer of the GI tract; contains many glands

epithelium

lines the lumen of the mucosa in the GI tract

lamina propria

mucosa connective tissue supporting the epithelium; contains lymphatic tissue (MALT)

muscularis mucosae

part of the mucosa that is composed of a thin layer of smooth muscle in the GI tract

submucosa

connective tissue layer external to the mucosa; contains blood vessels, nerves, and lymphatics; may contain glands (found within the esophagus and duodenum only)

muscularis externa

layer of smooth muscle external to the submucosa; consists of a circular, longitudinal, and oblique layer (in stomach only)

serosa

connective tissue and simple squamous epithelium (mesothelium) that covers intraperitoneal organs

adventitia

connective tissue outer layer that covers retroperitoneal organs

oral cavity

function: ingestion, moisture production, and enzyme production

-recieves saliva from salivary glands

-lined by nonkeratinized stratified squamous epithelium

esophagus

function: conducts a food bolus from the oral cavity to the stomach

-mucosa with nonkeratinized stratified squamous epithelium and goblet cells

-submucosa has mucus secreting glands

-covered externally by adventitia

goblet cells

mucus secreting cells in the esophagus

stomach

function: mechanical and enzymatic breakdown of food

-muscularis externa has an oblique layer in addition to circular and longitudinal layers

-epithelium secretes enzymes

-mucosa folded into rugae

rugae

the folds in the mucosa lining the stomach

oblique layer

the muscularis externa of the stomach has an _____________________ in addition to the circular and longitudinal layers

simple columnar

stomach mucosa is lined by _______________________ epithelium

gastric pits

form depressions in the stomach

gastric glands

____________ in the lamina propria of the stomach mucosa secrete pepsinogen, hydrochloric acid, and mucus

small intestine

function: enzymatic digestion and nutrient absorption

three component: duodenum, jejunum, and ileum

villi

projections of mucosa increasing small intestine surface area; contain blood vessels and lymph channels (lacteals) - glands are located in between

lacteals

Specialized lymphatic capillaries in the small intestine

microvilli

small projections of villi from epithelial cells (enterocytes)

simple columnar

the mucosa of the small intestine is lined by __________________ epithelium

enterocytes

major absorptive cells of the epithelium which have microvilli

duodenum

the first portion of the small intestine; receives bile and pancreatic enzymes; has long leaf-like villi

brunner glands

within the submucosa of the duodenum; secrete bicarbonate to neutralize stomach contents

jejunum

the second portion of the small intestine responsible for nutrient absorption; epithelium is mostly composed of enterocytes; contains long, finger-like villi are present

ileum

the third portion of the small intestine; contains many goblet cells and Peyer patches (lymphoid tissue); contains short, broad villi

colon

function: water and electrolyte absorption

lined by simple columnar epithelium; enterocytes absorb water and electrolytes; goblet cells secrete mucus

simple columnar

the colon is lined with __________________ epithelium

long, short, no

the duodenum and jejunum contain __________ villi

the ileum contain __________ villi

the colon contains _________ villi