1. GIT 2 – HISTOLOGY
Dr. ANAND SRINIVASAN

2. LEARNING OUTCOMES Able to :
Describe, identify and draw the histological features of :
Small intestine
Large intestine
Rectum & Anal canal

3. SMALL INTESTINE Divided into duodenum, jejunum and ileum
Luminal surface is increased for absorption by
Plica circulares (valves of Kerckring)
Intestinal villi
Microvilli

4. GENERAL HISTOLOGICAL FEATURES – SMALL INTESTINE
MUCOSA
EPITHELIUM
Simple columnar epithelium with goblet cells
Epithelium and lamina propria form intestinal villi
Presence of glycocalyx for protection and adsorption of pancreatic enzymes.
Crypts of Lieberkuhn containing goblet cells, columnar cells and Paneth cells
Paneth cells secrete lysozyme, located in base

6. LAMINA PROPRIA MUSCULARIS MUCOSA Connective tissue
Same as Gen. plan of GIT

7. SUBMUCOSA MUSCULARIS EXTERNA SEROSA Shows regional variation
Duodenum  Brunner’s gland
Ileum  Peyer’s patches
Jejunum  None of the above
MUSCULARIS EXTERNA
Same as Gen. plan of GIT
SEROSA

8. DUODENUM – Key histological features
Leaf like villi
Brunner’s glands (mucous, branched, coiled tubular) in submucosa opening into crypts.
Enteroendocrine cells secrete
Urogastrone – inhibit HCl
Secretin & Cholecystokinin – regulate pancreatic secretion
Disrupted muscularis mucosae

10. JEJUNUM – Key histological features
Finger like villi
No glands or lymphatic nodules in submucosa

11. ILEUM – Key histological features
Thin and slender villi
Peyer’s patches (aggregated lymphatic follicles) in submucosa

12. LARGE INTESTINE
Consists of Caecum, Appendix, Colon, Rectum and Anal canal
Absence of intestinal Villi
Has bacteria responsible for synthesis of Vitamin B12 & Vitamin K
Produces plenty of mucus that lubricates and facilitates easy passage of faeces

14. VERMIFORM APPENDIX
Gen. histological features of small intestine with following modifications
No Villi
Few short crypts
Small lumen
Lymphoid follicles in lamina propria
Disrupted muscularis mucosae

16. CAECUM & COLON
Gen. histological features of small intestine with following modifications
No Villi
Well developed crypts with plenty of goblet cells
Paneth cells Absent
Outer longitudinal layer of muscularis externa modified into “Taenia coli”
Fat filled pockets in serosa “Appendices epiploicae”

18. RECTUM
Gen. histological features of small intestine with following modifications
Long crypts of Lieberkuhn
Lymphoid tissue less abundant in lamina propria
Absent Taenia coli
Serosa replaced by adventitia in lower part

19. ANAL CANAL
Gen. histological features of small intestine with following modifications
EPITHELIUM
Above anal valves – stratified cuboidal
At anal valves – stratified squamous non keratinized
At anal orifice – stratified squamous keratinized
No crypts, No muscularis mucosae
Inner circular layer thick  anal sphincter
Smooth muscle changes to skeletal muscle at orifice

22. APPLIED ASPECTS

23. FURTHER READING Wheater’s Functional Histology
Cell Biology & Histology – Board Review Series
Microanatomy workbook – RAKMHSU