The rectum is approximately 12 cm in length and starts at the level of S3 as a continuation of the sigmoid colon. The puborectalis part of the pelvic floor forms a sling around the lower end at the junction with the anal canal. The rectum is commonly depicted in anatomic drawing as being dilated, causing the other pelvic organs to be pushed forward. This is because the original drawings were taken from cadavers but in the live patient the rectum is often empty allowing the other structures to lie supported on the pelvic floor.
The mucosa of the rectum is columnar and this is surrounded by inner circular and outer longitudinal fibres of smooth muscle. The serosal surface is covered by peritoneum.
The blood supply is from the superior rectal artery from the inferior mesenteric artery, and the middle and inferior rectal arteries arise from the posterior division of the internal iliac artery. The nerve supply is from the inferior hypogastric plexus and ensures the rectum is sensitive to stretch only.
A clear knowledge of anatomy is required for many gynaecological diagnoses and certainly for surgery. Many clinicians do not gain a full understanding of pelvic anatomy until they start operating and then rarely refer back to anatomical textbooks. The advent of more sophisticated pelvic floor surgery and especially minimal access surgery has modified the skills required of a gynaecological surgeon which necessitates the need for greater practical anatomical knowledge.
Shah Farthing & Richardson Lennard (2003) The Interactive Pelvis & Perineum: Female. Primal Pitures Ltd, www.primalpictures.com Snell R. Clinical Anatomy for Medical Students. London: Little Brown & Co.
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