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Gastrointestinal tract II: esophagus, stomach, small intestine,

large intestine, appendix2019/2020

HISTOLOGY OF ALIMENTARY CANAL

The histology of the alimentary canal often is discussed in terms of four broad layers: the (1) mucosa, (2) submucosa, (3) muscularis externa, and (4) serosa (or adventitia).

These layers are similar throughout the length of the digestive tract but display regional modifications and specializations.

Alimentary tract. Layer contents are generalized.

Esophagus

“Atlas of Descriptive Histology” Michael H. Ross, Wojciech Pawlina, Todd A. Barnash. 2009

Mucosal and submucosal glands are found in the esophagus.

Slide no. 34

Slide no. 34 Esophagus

Epithelium

THE STOMACH has 4 gross anatomical regions, but only 3 histological regions:(1) the body (corpus) and fundus which are similar histologically(2) the cardia(3) the pylorus

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Fundus/Body Pylorus

Body region including fundus:

➢ The pit : gland ratio is 1:4, that is the pits are short, but the glands are 4 times longer.

➢ The pits are lined by surface mucous cells and the glands are called gastric glands (fundicglands).

➢ The gastric glands are simple tubular glands lined by a simple columnar epithelium

➢ Unlike the cardiac and pyloric glands which are highly coiled, these are relatively straight.

Stomach fundus

Slide no. 35

5 major cell types:

(1) mucous neck cells

(2) chief cells (peptic cells)

(3) parietal cells (oxynticcells)

(4) stem cells

(5) gastroenteroendocrinecells (calledenterochromaffin cellsbecause of their stainingaffinity for chromicacid salts)

Gastric gland proper

Gastric gland

Fundic (or oxyntic) glands: oxyntic (or parietal) and chief cells

Slide no. 35

Parietal cells

(acidophilic)

Chief cells

(basophilic)

Pyloric region:

➢ The pits are lined by the surface mucous cells, but the pits

are very long, with a pit : gland ratio of 2 or 3:1.

➢ The short glands are called pyloric mucous glands, and

they are also divided into an isthmus and gland proper

that is mucous and similar to the cardiac glands in having

round nuclei. Mucosa

Muscularis mucosae

Slide 36

Duodenum

Slide no. 37

Mucosa

Submucosa with Brunner’s glands

Muscularis externa

Small intestine

Muscularis ex.

Serosa

Submucosa

Mucosa

Serosa

Muscularis ex. – 2 layers

Slide no. 38

Mucosa:

villi +

crypts

Small intestine – intestinal villi

Intestinal villi:

simple columnar epithelium

with goblet cells +

lamina propriaSlide no. 38

Magnification 10x

Magnification 4x

Small intestine – crypts & Paneth’s cells

Paneth cells

Paneth cells

Large intestine

Mucosa Submucosa

Muscularis

mucosae

Mucosa

Slide no. 39

The large number of goblet cells which characterize crypt epithelium

SubmucosaC

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Auerbach’s myenteric plexuses

Circular layer

(longitudinal

sections)

Longitudinal

layer (cross

sections)

Myenteric

plexuses

Slide no. 38/39

Lymphatic nodules are a standard feature of the appendix.

AppendixSlide no. 79