The Digestive System

Gastrointestinal tract (GIT)and the

Accessory organs and glands

General Histological Features

L

EpitheliumLamina

propriaMuscularis

mucosae

1. Mucos

a

2. Submucosa

Inner circular

Outer longitudinal

3. Musculari

sexterna

4. Serosa / adventit

ia

*Myenteric plexus/ Auerbachs plexus

Pharynx

Respiratory pharynx oropharynxSuperior portionLined by respiratory epithelium

Inferior portionLined by nonkeratinized stratified squamous epithelium

Esophagus Characteristic features:

Mucosa lined by nonkeratinized stratified squamous epithelium

Submucosa with esophageal glands (varies as to segment)

Muscularis externa Upper portion with skeletal muscles Middle third with mixed skeletal and smooth muscle Lower third with smooth muscle

Points of comparison

uppermost portion

Middle 1/3 Lower 1/3

1. Muscularis mucosae

Absent in the beginning

PresentPresent

2. Muscularis externa Skeletal muscle

(inner circular & thick outer longitudinal)

Skeletal & smooth muscle

(inner smooth muscle & outer skeletal muscle)

Smooth muscle (inner circular

& outer longitudinal)

3. Submucosal glands Absent few abundant

4.Adventia Only fibrosa Only fibrosa Only serosa

Comparison Between various Portions of Esophagus

* Presence of glands at transition between middle and lower 1/3

Esophageal glands

Smoothmuscle

Skeletalmuscle

Esophageal glands

Stomach Characteristic features:

Mucosa is complex 2-3 layers muscularis mucosae Gastric glands Gastric pits

Presence of rugae

Muscularis externa (3 layers) Inner oblique Middle circular Outer longitudinal

Variations in the glands (crypts, pits, ducts)

Esophageal-gastric junction

* * * * ***

Gastric mucosa epithelial cell types:

Surface mucous cells

Undifferentiated cells

Neck mucous cells

Parietal/oxyntic cells

Chief/zymogenic cells

Enteroendocrine cells

Small intestine(duodenum, jejunum, ileum)

Characteristic features:

Composition and organization of mucosa

Plicae circularis/ valves of Kerckring

Muscularis externa (2-layered)

Mucosa of the Small intestine:

Presence of villi

Intestinal glands/ Krypts of Lieberkuhn

Enterocytes/absorptive cells

Goblet cells

M cells

Paneth cells

Enteroendocrine cells &Undifferentiated cells

Regional differences

Duodenum

Presence of Brunners gland in the submucosa

Typically with leaflike to fingerlike villi

Relatively few goblet cells**

*

* *

*

*

Jejunum

neither Brunners glands nor Peyers patches

With long leaflike villi

Many plicae circularis

Intermediate number of goblet cells

Ileum

Lamina propia with many Peyers patches

With short, broad-tipped villi

Relatively abundant goblet cells

Large intestine/colon

Mucosa

with simple columnar epithelium Abundant goblet cells Absence of villi Deep cyrpts of Lieberkuhn

No mucosal folds except in the rectum (rectal columns of Morgagni)

Submucosa Hemorrhoidal plexus of veins ( in the lower rectum)

Muscularis externa Smooth muscle (longitudinal bands) *** taeniae coli

Adventitia/Serosa

Anal canal Mucosa

with short crypts ---disappearing (1st 2 cm) Stratified squamous epithelium (to the opening)

Submucosa with sebaceous glands and sweat glands

Muscularis externa with thickened inner circular smooth muscle

Appendix

Resembles the colon except for:

relatively small lumen

Fewer and shorter crypts

More lymphoid nodules

Without taeniae coli