Histology Pre-lab. # 10

Intestines – Jejunum, Ileum, Colon & Appendix

By Prof. Dr. Ansari

( MBBS semester I ) Wednesday, April 19, 2023 1

Objectives of the lab.

• To identify the microscopic structure of Jejunum, Ileum, colon & appendix.

• To differentiate the small intestine from the large intestine microscopically.

• To learn the structure of a Villus.• To learn the GALT.

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Jejunum is part of small intestine next to duodenum

• Microscopy of jejunum is similar to any part of GIT.

• It shows tunica mucosa having simple columnar epithelium, Plica circularis, Villi and goblet cells.

• The tunica sub mucosa having blood vessel & nerve endings.

• Tunica Muscularis externa having circular and longitudinal smooth muscles.

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4Tunica Muscularisexterna

VillusVillus

Sub MucosaSub Mucosa

JEJUNUM

Peyer’s patches are special feature of Ileum

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Plica circularis is a fold of mucosa with a core of sub mucosa, a feature of small intestine

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Plica circularis

The epithelium appears columnar and contains cells with deeply invaginated basal surfaces - microfold cells

or M-cells.

• These M- cells are belonging to immune system.

• Found near the lymphoid follicles.

• These are part of GALT, gut associated lymphoid tissue

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Structure of a Villus• A Villus is a finger like

projection of mucosa.• Villus is made of a core of

lamina propria having a radicle of lacteal, a capillary, a venule and smooth muscle fibers.

• Villus contain absorptive cells, goblet cells, and APUD cells.

• Villi are seen only in small intestine.

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Colon is large intestine• Histological it has more goblet cells in

their mucosa.

• No Villi in the mucosa.

• Sub mucosa having lymphoid infiltration of GALT.

• Muscularis externa has inner circular smooth muscles and outer longitudinal muscles distributed in the tinea coli (longitudinal bands of smooth muscles).

• Large intestines are identified by the excessive presence of goblet cells.

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Taenia coli are features of large intestine

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TaeniaColi are Longitudinal

muscular bands

Appendix is a part of large intestine

Sub mucosa is highly infiltrated with GALT

Mucosa of appendix

• Has simple columnar epithelium.

• Goblet cells.• Lumen is star shaped.• Sub mucosa is loaded

with lymphoid follicles.• Muscularis externa

shows inner circular and outer longitudinal smooth muscles.

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Crypts of Lieberkuhn are intestinal glands

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Longitudinal section Cross section

Applied anatomy

• Typhoid fever is the enteric fever, complicating to perforation of bowel.

• Colitis is the inflamation of the colon.• Appendicitis is the inflamation of appendix.• Meckle’s diverticulum is a developmental

anomaly of vitellointestinal duct.• Anal hemorrhoids are venous engorgements of

rectal veins leading to bleeding piles.• Colonoscopy is the endoscopy of colon.

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