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 Submucosa Muscularis externa Epithelium –coloncytes Intestinal gland- 0.5mm 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 Serosa / Adventitia

colon

colon

RECTUM Goblet cells abundant Glands deeper -0.75mm 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: Lamina propria: Muscularis mucosa: 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: Lamina propria: Stratified squamous non-keratinized Lamina propria: Crypts absent Muscularis mucosae: Broken –gradually indistinct Submucosa

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

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

MEDICAL APPLICATION Anal fissures Anal abscesses Hemorrhoids