Anatomy of Rectum

Tirunelveli Medical College Department of Anatomy

The Anatomy Of Rectum Presentation by K Hari Krishnan I Year MBBS (2008-’09) Tirunelveli Medical College Tirunelveli, Tamilnadu, India

Distal part of the large gut The pelvic part of the alimentary tract Introduction

Location Posterior part of the lesser pelvis In front of lower three pieces of sacrum and the coccyx

Extent Begins at the rectosigmoid junction at level of third sacral vertebra Ends at the anorectal junction 2-3 cm in front of and a little below the coccyx

Length 13 cm (5 in.) Diameter 4 cm (in the upper part) Dilated (in the lower part) Dimensions

Downwards and backwards Downwards Downwards and forwards Course

Flexures Antero-posterior flexures (2 in number) Sacral flexure Follows the curve of the sacrum and coccyx

Flexures Antero-posterior flexures Perineal flexure / Anorectal flexure 80Â° anorectal angle In the terminal part of the rectum At the anorectal junction Here the rectum perforates the pelvic diaphragm to become the anal canal

Flexures Lateral flexures (3 in number) – correspond to the transverse rectal folds Superior Convex to the right Intermediate Convex to the left Most prominent Inferior Convex to the right

Superior 1/3rd of the rectum Covered by peritoneum on the anterior and lateral surfaces Middle 1/3rd of the rectum Covered by peritoneum on the anterior surface Inferior 1/3rd of the rectum Subperitoneal – Devoid of peritoneum Peritoneal Relations

In males Upper 2/3rd Rectovesical pouch Coils of ileum Sigmoid colon Lower 1/3rd Fundus (base) of the urinary bladder Terminal parts of the ureters Seminal vesicles Ductus deferentes Prostate Visceral Relations Anterior

Visceral Relations Posterior In females Upper 2/3rd Rectouterine pouch, which separates the rectum from the uterus and from the upper part of vagina Coils of ileum Sigmoid colon Lower 1/3rd Lower part of vagina

Posterior Relations Bones Lower three pieces of sacrum Coccyx Ligaments Anococcygeal ligament Muscles Piriformis Coccygeus Levator ani Vessels Median sacral Superior rectal Lower lateral sacral Nerves Sympathetic chain with ganglion impar Ventral primary rami of S3, S4, S5, Co1 Pelvic splanchnic nerves Lymph nodes and lymphatics Fat

Arterial Supply Superior rectal artery Direct continuation of Inferior mesenteric artery Enters the pelvis by descending in the root of the sigmoid mesocolon and divides into right and left branches, which pierce the muscular coat and supply the mucous membrane They anastomose with one another and with the middle and inferior rectal arteries Middle rectal artery Small branch of anterior division of Internal iliac artery Run in the lateral ligaments of the rectum Supplies the muscular coat of the lower part of rectum Inferior rectal artery Branch of Internal pudental artery in the perineum Anastomoses with the middle rectal artery at the anorectal junction Median sacral artery Direct branch from the dorsal surface of Aorta near its inferior end Descends in the median plane Supplies the posterior wall of the anorectal junction

Venous Drainage Submucosal rectal venous plexus Surrounds rectum Communicates vesical venous plexus – males uterovaginal venous plexus – females 2 Parts: Internal rectal venous plexus Deep to the epithelium of rectum Drains into Superior rectal vein External rectal venous plexus External to the muscular wall of rectum Superior portion: drains into Superior rectal vein Middle portion: drains into Middle rectal vein Inferior portion: drains into Inferior rectal vein

Superior rectal vein Formed from Internal rectal venous plexus Consists of 6 main tributary veins Continues upwards as Inferior mesenteric vein Middle rectal vein Formed from the middle portion of External rectal venous plexus Pass alongside middle rectal artery Drains into the anterior division of Internal iliac vein on the lateral wall of the pelvis Inferior rectal vein Formed from the inferior portion of the Inferior rectal vein Drains into the Internal pudental vein Venous Drainage

Superior half of the rectum Pararectal lymph nodes, located directly on the muscle layer of the rectum Inferior mesenteric lymph nodes, via either the sacral lymph nodes or the nodes along the superior rectal vessels Inferior half of the rectum Sacral group of lymph nodes or Internal iliac lymph nodes Lymphatic Drainage

Nerve Supply Sympathetic nerve supply L1, L2 fibres Through Superior rectal and Inferior hypogastric plexuses Vasoconstrictor Inhibitory to musculature of rectum Motor to internal sphincter Carry sensations of pain Parasympathetic nerve supply S2, S3, S4 fibres Passes via pelvic splanchnic nerves and inferior hypogastric plexuses to rectal (pelvic) plexus Motor to musculature of the rectum Inhibitory to internal sphincter Carry sensations of pain and distension

Interior Longitudinal folds Present in lower part of the empty rectum Effaced during distension

Interior Transverse folds(Houston’s valves or plicae transversae recti) Marked in rectal distension Superior fold At beginning of rectum Projects from the right or the left wall Middle fold Above the rectal ampulla Projects from the anterior and right walls Largest and most constant Inferior fold About 2.5 cm below the middle fold Projects from the left wall Variable Occasional fourth fold About 2.5 cm above the middle fold Projects from the left wall

Supports Pelvic Floor Levator ani muscles Fascia of Waldeyer Condensation of pelvic fascia behind rectum Lower part of ampulla to Sacrum Encloses Superior rectal vessels and lymphatics Lateral ligaments of Rectum Denonvilliers fascia Pelvic peritoneum Perineal body

Digital Rectal Examination Examination to check for abnormalities of organs or other structures in the pelvis and lower abdomen To check for growths in or enlargement of the prostate gland in males. A tumor in the prostate can often be felt as a hard lump problems in female reproductive organs (uterus and ovaries) rectal bleeding or tumors in the rectum

Proctoscopy Proctoscopy - Visual examination of the rectum and anus Visualizing the interior of the rectum and anal canal Helps in revealing ulcers, abnormal growths and diverticula

Sigmoidoscopy Sigmoidoscope An endoscope for viewing the lumen of the sigmoid colon

Rectal Prolapse Rectocoele Protrusion of the mucous membrane and submucosa of the rectum outside the anus for approximately 1–4 cm Common in Children: 1 – 3 years Elderly people Middle-aged women

Partial Rectal Prolapse Rectal mucous membrane and submucous coat protrude for a short distance outside the anus Common in children

Complete Rectal Prolapse Procidentia Whole thickness of the rectal wall protrudes through the anus A sliding hernia through the pelvic diaphragm Common in adults Associated with rectal incontinence

Causes In infants Undeveloped sacral curve Reduced resting anal tone – diminished support to the mucosal lining of anal canal In children Diminution of fat in ischiorectal fossae Diarrhoea Severe whooping cough Sudden loss of weight Fibrocystic disease Neurological causes Mal-development of pelvis Rectal Prolapse

Causes In adults Haemorrhoids Torn perineum Straining from urethral obstruction Following operation for fistula in ano In the elderly Atony of sphincter mechanism Rectal Prolapse

Treatment Submucous injections Excision of the prolapsed mucosa Surgery Rectal Prolapse

Rectal Carcinoma Found mainly in Rectosigmoid junction Ampulla Bleeding per rectum Initial finding – Lymphatics around the bowel Later – lymph nodes along superior rectal and middle rectal arteries Venous spread – Superior rectal vein to portal vein Liver – secondary deposits

Rectal Carcinoma Treatment Rectal excision and total mesorectal excision Abdomino-perineal excision with a permanent colostomy Adjuvant preoperative radiotherapy Liver resection for liver metastases

Gray’s Anatomy: The Anatomical Basis of Clinical Medicine Gray’s Anatomy for Students Richard S. Snell – Clinical Anatomy by Regions Keith L. Moore – Essential Clinical Anatomy Last’s Anatomy - Regional and Applied Frank H. Netter – Atlas of Human Anatomy Bailey and Love’s Short Practice of Surgery Sources

Anatomy of Rectum

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