Anal Canal Anatomy PDF

GIT 2025 Anatomy Lecture(6): ANATOMY OF RECTUM, ANAL CANAL AND SPLEEN RECTUM Beginning: continuous with sigmoid colon at level of 3rd sacral vertebra End: at anorectal junction 2–3 cm in front of and below the tip of the coccyx. about...

GIT 2025 Anatomy Lecture(6): ANATOMY OF RECTUM, ANAL CANAL AND SPLEEN RECTUM Beginning: continuous with sigmoid colon at level of 3rd sacral vertebra End: at anorectal junction 2–3 cm in front of and below the tip of the coccyx. about 15 cm in length Peritoneal relations - upper ⅓ : covered by peritoneum - middle ⅓ : covered by peritoneum only anteriory The peritoneum is reflected superiorly onto the urinary bladder in males to form the rectovesical pouch, or onto the posterior vaginal wall in females to form the recto- uterine pouch (pouch of Douglas). - lower ⅓ : has no peritoneum Relations of the rectum - Anteriorly In male - Fundus of bladder - Seminal vesicle - Prostate - Ampulla of ductus deferentis In female - neck of uterus - Vagina - Posteriorly - Sacrum and coccyx - Piriformis - Median sacral vessels - Anterior branches of sacral and coccygeal nerves - Sacral sympathetic trunk - Laterally - Pelvic plexus - Superior and inferior rectal vessels - Levator ani Vessels and lymphatics of rectum A- Arteries 32 GIT 2025 Anatomy 1- Superior rectal artery: single artery, cont. of inf. mesenteric artery 2- Middle rectal artery: paired, from internal iliac artery 3- Inferior rectal artery: paired, from internal pudendal artery 4- Median sacral artery: from abdominal aorta B- Veins 1- Superior rectal veins: from internal rectal plexus in rectal submucosa→ superior rectal vein→ inferior mesenteric vein (portal circulation) 2- Middle rectal veins: drain into IIV→ IVC(systemic circulation) 3- Inferior rectal veins: from external rectal plexus→ internal pudendal vein (systemic circulation) C- Lymphatic drainage: to following nodes: - Superior rectal LN - Inferior mesenteric LN - Pararectal LN - Internal iliac LN - Sacral LN Anal Canal It is about 4 cm long, descending downward and backward as a continuation of rectum to anus. Relations: - Anteriorly: perineal body - Posteriorly: anococcygeal body. - Laterally: ischiorectal fossae. Division: Divided into: Upper half: derived from hindgut (endoderm) Lower half: derived from the proctodeum (ectoderm) The two parts have different blood supply, nerve supply and lymphatic drainage. 33 GIT 2025 Anatomy Upper ½ (Endodermal) Lower ½ (Ectodermal ) Epithelium Columnar (colonic – GIT) Stratified (skin) Arterial supply Superior rectal A Inferior rectal A Venous drainage Superior rectal V Inferior rectal V → COMMUNICATE together → porto-caval (systemic) anastomosis. Lymphatic Para-aortic LN Superficial inguinal LN drainage [pararectal lymphatics → to both a)- internal iliac nodes (middle rectal A), and b)- para-aortic lymph nodes at the origin of inferior mesenteric A.] Nerve supply Autonomic- Insensitive Somatic- Sensitive Anal sphincters A- Internal - Smooth muscle(thickened circular muscle coat) - Surrounds upper two-thirds of anal canal - Autonomic nerve supply B- External - Striated muscle - Surrounds lower two-thirds of anal canal - Three parts→subcutaneous, superficial and deep - Somatic n. supply→ pudendal nerve and branches of S4. SPLEEN 34 GIT 2025 Anatomy Site: in the LT hypochondrium between fundus of the stomach and the diaphragm. Surface anatomy : Its long axis lies in the plane of Lt 10 th rib making an angle about 45 degrees with horizontal plane. Its posterior border is approximately 5 cm from the 10 th thoracic vertebrae. Its anterior end usually reaches the mid-axillary line. Features of the spleen: the spleen has: - 2 surfaces: diaphragmatic(convex and smooth) and visceral surface (concave, irregular and show hilum of spleen). - 2 borders: superior(sharp and show splenic notch) and inferior border (smooth). - 2 ends: anterior(expanded like a border) and posterior end (rounded). Peritoneal connections of the spleen: spleen is entirely covered by peritoneum and has the following ligaments: 1- The splenorenal(lienorenal) ligament: from Lt kidney to splenic hilum. It contains; splenic vessels, tail of pancreas and LN of the spleen 2- The gastrosplenic ligament: between hilum of spleen and greater curvatures of stomach. Its contents are; - The short gastric arteries - left gastroepiploic branches - lymphatics and LN of the spleen Vascular supply and lymphatic drainage: A- Arteries: splenic artery: runs in splenorenal ligament. Then enter the hilum of spleen B- Veins: to splenic vein C- Lymphatics: pass out of the hilum into lymphatic vessels that accompany the splenic artery and vein into the coeliac nodes (red pulp of the spleen has no lymphatics) 35