I. General Description and Considerations Digestive System I. General Description and Considerations

A. Paradox of similarity and change All organs of the GI tract are modifications of a simple tube Epithelium of the entire tract is derived from a single embryonic germ cell layer All organs have some function related to digestion All areas of the tract have basically the same histological layers

A. Paradox of similarity and change However, Abrupt changes occur in the epithelium from one organ to the next Drastic modifications of the mucosa occur from one organ to the next Each organ along the tract performs a separate and unique function related to digestion

B. General description Mucosa Submucosa Muscularis externa Adventitia Epithelium Lamina propria Muscularis mucosa Submucosa Muscularis externa Adventitia

General Plan of the GI Tract

Digestive System II. Esophagus

A. General description and functions Length, location, & relationships Innervation Functions

II. Esophagus General Mucosa Submucosa Muscularis Adventitia

B. Mucosa Non-keratinized stratified squamous epithelium Lamina propria Muscularis mucosa

C. Submucosa Contributes to large longitudinal folds of esophagus - these smooth out during swallowing

C. Submucosa 2. Contains esophageal glands - compound tubuloalveolar, mucus secreting

D. Muscularis externa Upper one-third Middle one-third Lower one-third Innervation

E. Adventitia Intrathoracic portion blends with surrounding dense irregular FECT Below diaphragm covered with visceral peritoneum

Gastro-Esophageal Junction

Gastro-Esophageal Junction

Gastro-Esophageal Junction

Esophageal Ulcer

Digestive System III. Stomach

A. General description & functions Role in digestion and storage 4 gross anatomic vs. 3 histological divisions Rugae

Stomach Regions & Glands

B. Mucosa Surface esophageal-gastric junction - abrupt change from stratified squamous to simple columnar gastric pits - fine furrows, lead into glands simple columnar epithelium - forms sheet gland, all mucus secreting, mucus has a basic pH

Gastric Lining Cells & Pits

B. Mucosa Gastric gland structure & nomenclature simple, branched tubular glands - occupy entire thickness of mucosa each gland has a neck, body, and base

B. Mucosa Gastric gland structure & nomenclature simple, branched tubular glands - occupy entire thickness of mucosa each gland has a neck, body, and base

B. Mucosa Lamina propria occupies space between glands and pits richly vascularized and slips of smooth muscle from muscularis mucosa

B. Mucosa Cardiac glands in cardiac region of stomach, near esophageal orifice length of gland approximately equal to depth of pit mostly mucus secreting cells with a few parietal and enteroendocrine cells primary function is to produce a protective mucus secretion

B. Mucosa Cardiac glands

B. Mucosa Fundic glands located in fundic and body regions of stomach one or more open into each gastric pit, glands are much longer than their pits are deep classified as simple branched tubular closely packed, perpendicular to surface major source of gastric juice

B. Mucosa Fundic glands

B. Mucosa Fundic gland cells Mucus Neck Parietal Chief Enteroendocrine

Fundic Stomach

Gastric Pits

Fundic Glands – Neck & Body

Parietal Cell

Fundic Glands - Base

Enteroendocrine Cells

Enteroendocrine Cell

B. Mucosa 7. Pyloric glands

Pyloric Stomach

Meisner’s Plexus

Muscularis Externa

Auerbach’s Plexus

Gastric Ulcer

Gastroduodenal Junction

Gastroduodenal Junction