Histology of the digestive system

Gastrointestinal tract (GI tract) 1.Mouth: a.Internal: nonkeratinized stratified squamous epithelium b.Middle: buccinator muscles, bone

2. pharynx: skeletal muscle; nonkeratinized stratified squamous epithelium

3. esophagus: a. nonkeratinized stratified squamous epithelium b. skeletal (superior); smooth muscle (inferior)

4. esophagus to anal canal Deep to superficial Mucosa –Epithelium: touches food Nsse – protection Simple columnar (stomach/intestines)– secretion/absorption exocrine cells (mucus) endocrine cells (hormones) –Lamina propria (conn.)- blood/lymph vessels, MALT –Smooth muscle – makes folds, inc. SA

Submucosa –Binds mucosa to muscularis –Blood/lymph vessels/neurons

Muscularis –Skeletal muscle until middle esophagus (swallowing); external anal sphincter –Smooth muscle Inner: circular fibers Outer: longitudinal fibers

Serosa: connective and simple squamous epithelium (reduce friction)

ACCESSORY ORGANS

pancreas Small clusters of glandular epithelial –99%: called acini (exocrine function – secrete pancreatic juice for digestion) –1%: called pancreatic islets (endocrine function)

liver Consists of many lobules –Contains epithelial cells called hepatocytes arranged irregularly around a central vein. Capillaries, called sinusoids, are highly present and contain fixed phagocytes (to removed WBCs and RBC, bacteria, etc)

gallbladder Mucosa is simple columnar epithelium