Anatomy study note · Pelvis

Rectum

About 13 cm long, it begins in front of S3 as the continuation of the sigmoid colon, follows the curve of the sacrum and coccyx, and ends in front of the coccyx tip by piercing the pelvic diaphragm to become the anal canal.

Key points

• 13 cm; S3 → tip of coccyx.
• Peritoneum: upper third front + sides, middle third front, lower third none.
• Superior (IMA), middle (internal iliac), inferior (internal pudendal) rectal arteries.
• Portal–systemic anastomosis in the anal canal.
• Male: prostate in front; female: vagina in front.
• Rectum: dorsal cloaca (urorectal septum).
• Pectinate line = endoderm–ectoderm junction.
• Anal canal: columnar → stratified squamous at the anal valves.
• Colon: no villi, many goblet cells.

The full note in the atlas also covers

Relations · Features · Blood supply · Nerve supply · Lymph drainage · Histology · Development · Clinical notes

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Written from

• Snell’s Clinical Anatomy by Regions, 10th ed., ch. 9, PDF pp. 1074–1083
• Inderbir Singh’s Human Embryology, ch. 13, PDF pp. 176–177, 184, 188–191
• BRS Cell Biology & Histology, 7th ed., ch. 16, PDF pp. 296–297, 298

More from the pelvis

• Sacral plexus
• Sacrococcygeal joint
• Sacroiliac joint
• Sacrotuberous and sacrospinous ligaments
• Sacrum
• Seminal vesicle
• Sigmoid colon
• Urinary bladder
• Uterine artery
• Uterine tube
• Uterus
• Vagina

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