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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.
2
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.
3
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
7
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.
8
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.
9
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.
12
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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