HISTOLOGY OF LARGE INTESTINE BY DR SOBIA IBRAHIM

HISTOLOGY OF LARGE INTESTINE BY DR. SOBIA IBRAHIM

LARGE INTESTINE • Has caecum, colon, rectum and anal canal. • Main functions • Absorption of water • Formation of faecal mass • Production of mucus

• Its wall follows the same four layered pattern • From inner to outer • Mucosa • Sub mucosa • Muscularis externa • Serosa/adventitia • But • NO villi • No plica circularis

• Appendices Epiplocae • Tenia coli

COLON NO villi / plica circularis Mucosa Epithelium –coloncytes Intestinal gland- 0. 5 mm deep, lined by columnar cells, goblet cells, enteroendocrine & stem cells Lamina propria- rich in lymphatic tissue, BV, lymphocytes, plasma cells, collagen Muscularis mucosae- prominent Submucosa Muscularis externa Inner circular Outer longitudinal – taeniae coli o Serosa / Adventitia

• colon

COLON

RECTUM • Goblet cells abundant • Glands deeper -0. 75 mm • Complete muscle coat • Rest same

COMPARISON

MEDICAL APPLICATION • • Adenocarcinoma of colon Very common in old age Most common tumor of old age in developed countries Causes Low fiber intake Ulcerative colitis/ other diseases of gut Family history

APPENDIX • Irregular lumen • Few short intestinal glands • Epithelium • • • Columnar cells Goblet cells- few Paneth cells- few Enteroendocrine cells M cells • Lamina propria • Diffuse lymphocytic infiltration • Lymphatic nodules • • Muscularis mucosae- disrupted Submucosa- lymphatic tissue etc. Muscularis externa- two layers Serosa

APPENDIX

MEDICAL APPLICATION • ACUTE APPDICITIS • Infection & inflammation of appedix • Lymphoid follicle inlarges • Wall rupture

ANAL CANAL(UPPER 1/3) • Epithelium: • Simple columnar with goblet cells • Lamina propria: • Intestinal glands -short • Muscularis mucosa: • Inner circular • Outer longitudnal • Submusoa: • Loose CT • Branched tubular glands lined with mucous cells • Numerous thin walled veins. Internal hemorrhoidal veins (Piles)

ANAL CANAL (MIDDLE 1/3) • Epithelium: • Stratified squamous nonkeratinized • Lamina propria: • Crypts absent • Muscularis mucosae: • Broken –gradually indistinct • Submucosa

ANAL CANAL (LOWER 2 CM) • Epithelium: • Stratified squamous keratinized • Sweat glands • Sebaceous glands • Lamina propria & Submucosa: • No distinction • Muscularis mucosa: • Absent

• MUSCULARIS EXTERNA • Inner circular – internal anal sphincter • Outer longitudinal • Outermost – skeletal muscle – external anal sphincter • ADVENTITIA

MEDICAL APPLICATION • Anal fissures • Anal abscesses • Hemorrhoids