RectumThe rectum continues with the sigmoid colon proximal to the rectosigmoid junction (S3) and with the anal canal distally1. The rectum has a sacral flexure that follows the curve of the sacrum and coccyx1. The anorectal flexure is an S-shaped flexure that has a sharp posterior-inferior antero-inferior curve at the tip of the coccyx and penetrates the pelvic diaphragm1. It is held by the puborectalis sling through the puborectalis muscle1. Finally, the rectum also presents lateral flexures due to transverse rectal folds1. There is superior, intermediate, and inferior lateral flexion. Rectal relations1: • Inferior o Pelvic diaphragm (levator ani) o Anococcygeal ligament • Anterolateral o Superior rectus peritoneum • Anterior o Middle rectus peritoneum o Females Retrouterine pouch Vagina o Males Retrovesicular pouch Fundus of urinary bladder Terminal parts of the ureters Vas deferens, seminal glands and prostate • Lateral or pararectal fossae • Posterior o 3 inferior sacral vertebrae o Coccyx o Anococcygeal ligament o Median sacral vessels o Lower ends of the sympathetic trunk and sacral plexusThe arterial supply of the proximal rectum comes from the 'superior rectal artery from the inferior mesenteric artery1. The middle and inferior rectus are supplied by the middle rectal arteries which are branches of the internal iliac arteries1. The anorectal junction and the inferior anal canal are supplied by the inferior rectal artery from the internal pudendal artery1. The superior and inferior rectal arteries anastomose. Venous drainage flows through the superior, middle and inferior rectal veins1. The superior and middle rectal veins drain into the terminal portal vein, while the inferior rectal vein drains... center of paper... the upper half of the anal canal drains deep into the internal iliac lymph nodes and then into the internal iliac lymph nodes. from the common iliac lymph nodes to the lumbar lymph nodes1. The lower half drains superficially into the superficial inguinal lymph nodes1. The upper half of the anal canal has visceral innervation1. It is involuntary and is supplied by the hypogastric plexus with sympathetic, parasympathetic, and visceral components traveling to S2-S41. The lower half has a voluntary and somatic innervation from the lower anal (rectal) nerves, which branch from the pudendal nerve1. This part of the canal is sensitive to pain, temperature and touch1. Works Cited1. Moore KL, Dalley AF, Agur AMR. Clinically oriented anatomy. 6th ed. Philadelphia: Lippincott Williams & Wilkins; 2010, p.246-253; 411-414.2. Netter, F.H. Atlas of human anatomy. 5th ed. Philadelphia: Saunders Elsevier; 2009. Plate 373.