Rectum and Anal Canal PDF: Anatomy Study Guide

‫بسم هللا الرحمن الرحيم‬ Rectum and Anal canal by Prof. Dr. Ehab Elzawawy  Learning Objectives Describe the beginning, termination and flexures of rectum. Describe the blood supply, nerve supply & lymphatic drainage of rectum. Know key relations: structure...

‫بسم هللا الرحمن الرحيم‬ Rectum and Anal canal by Prof. Dr. Ehab Elzawawy  Learning Objectives Describe the beginning, termination and flexures of rectum. Describe the blood supply, nerve supply & lymphatic drainage of rectum. Know key relations: structures felt during per-rectal (PR) examination. Describe the interior of anal canal. Describe the blood supply, nerve supply & lymphatic drainage of anal canal. Describe the internal & external anal sphincters. Know some important clinical points.  Rectum Beginning: -At S3 as a continuation of the sigmoid colon. Course: -Follows the concavity of sacrum & coccyx (sacral flexure). Termination: -Ends at the recto-anal junction, in front and below the tip of coccyx by bending posteriorly (perineal flexure). Its lower part is dilated and called rectal ampulla.  Rectum Peritoneal covering Upper 1/3rd front and sides are covered by peritoneum. Middle 1/3rd front is only covered by peritoneum. Lower 1/3rd has No peritoneal covering.  Rectum Lateral curvatures (flexures): a. Upper flexure: to the right side. b. Middle flexure: to the left side. c. Lower flexure: to the right side. Beginning and end are in the midline.  Rectum Antero-posterior flexures: a. Sacral flexure: - Follows the concavity of the sacrum. b. Perineal flexure: - At the recto-anal junction.  Interior of rectum: Transverse horizontal mucosal folds: valves of Houston Per-Rectal (P/R) Examination -In male: prostate tumors. -In female: tumors of cervix and posterior vaginal wall.  Arterial supply Venous drainage Blood supply 1. Superior rectal vein continues 1. Superior rectal artery: - It is the continuation of up as inferior mesenteric vein inferior mesenteric artery. which drains into the splenic vein. (Portal circulation) - It supplies the rectum and upper half of anal canal. 2. Middle rectal artery: 2. Middle rectal vein: It arises from the anterior Drains into internal iliac vein. division of internal iliac (Systemic circulation) artery. 3. Inferior rectal vein: 3. Inferior rectal artery: Drains into internal iliac vein. It arises from internal (Systemic circulation) pudendal artery. Clinical note: Superior, middle, and inferior rectal veins anastomose with each other in submucosa of rectum and anal canal. Hemorrhoids (piles): is the dilation of the veins at the site of anastomosis.  Nerve supply: 1. Sympathetic: sacral splanchnic nerve 2. Parasympathetic: pelvic splanchnic nerve  Lymph drainage: 1. Upper half drains to inferior mesenteric L.Ns. 2. Lower half drains to internal iliac lymph nodes. A 2-year-old boy is presenting with chronic severe constipation, abdominal distension, and failure to thrive. The mother is saying that passage of meconium was delayed. What is the most probable diagnosis? A: Rectal atresia B: Hirschsprung disease C: Functional constipation D: Hyperganglionosis E: Celiac disease Anal canal  Anal canal  Terminal part of alimentary canal.  Length: 4 cm.  Direction: backward & downward.  Beginning: anorectal junction.  Termination: external anal orifice.  Anal canal  Relations: Posterior: Anococcygeal body. Anteriorly: Perineal body.  Anal canal  Relations: Laterally: upper part: levator ani. lower part: ischioanal fossae.  Ischioanal fossa Boundaries:  Lateral: obturator internus, ischium, sacrotuberous ligament.  Medial: levator ani, anal canal.  Apex: origin of levator ani from white line.  Ischioanal fossa Contents:  Isciorectal pad of fat.  Inferior rectal nerve and vessels.  Pudendal nerve and vessels in pudendal canal.  Posterior scrotal or labial nerves.  Perineal branch of S4.  Perforating cutaneous nerve. Interior of anal canal: I-Upper mucous membrane part: lined by columnar epithelium 1. Anal columns: 6-10 vertical mucosal folds. 2. Anal valves: Lower ends of anal columns united by short transverse folds. Interior of anal canal: I-Upper mucous membrane part: lined by columnar epithelium 3. Anal sinus: Depression in mucosa above each valve. 4. Pectinate line: At anal valves, junction of ectoderm& endoderm. II- Middle Transitional Zone (Anal Pecten): 1- Non-keratinized stratified squamous epithelium. 2- White line of Hilton: Lower limit of Pecten, Situated at lower border of internal anal sphincter. III- Lower cutaneous part: Lined by true skin, contains sweat & sebaceous glands.  Anal sphincters 1. Internal anal sphincter: - Smooth, involuntary. - Circular muscle fiber, continuous with that of rectum. - Supplied by sympathetic and parasympathetic nerves.  Anal sphincters 2. External anal sphincter: -Striated, voluntary. -Surrounds whole length. -Supplied by inferior rectal nerve and perineal branch of S4.  Anal sphincters 2. External anal sphincter: Parts: I) Proximal: Deep part. II) Distal: Subcutaneous Part& Superficial Part. Blood supply, nerve supply and lymph drainage of anal canal: Upper part Lower part Blood -It is supplied by superior rectal -It is supplied by: supply artery. 1- Middle rectal artery of internal iliac artery. - It is drained by superior rectal vein 2- Inferior rectal artery of internal pudendal (portal circulation). artery. -The corresponding veins drain into internal iliac vein (systemic circulation.) Nerve Above pectinate line by autonomic Below pectinate line by inferior rectal nerve supply nerve fibers. (Sensitive to pain &touch). Lymphatic Above pectinate line into internal Below the pectinate line into superficial drainage iliac LNs. inguinal LNs. Bleeding per-rectum PILES/ HAEMORRHOIDS -Enlarged submucosal veins: occur in 3, 7, & 11 o’clock position. -They are a common cause for passing blood during and after defecation. -The presence of hemorrhoids may be a sign of portal hypertension. Bleeding per-rectum Colorectal cancer -In the 'back of every clinician's mind' is the concern that the blood passed from the rectum could be caused by an underlying colonic or rectal malignancy.  Carcinoma of the colon and rectum - The colon and rectum are in proximity to other organs. - A tumor of the rectum, for example, could invade the uterus or bladder. - U/S, CT scan, MRI. - Lower GIT Endoscopy: Proctoscopy, colonoscopy. Bleeding per-rectum Anal Fissure Thank you