ASCRS Ch01 — Anatomy and Embryology of the Colon, Rectum, and Anus

Citation: Carmichael JC, Mills S. "Anatomy and Embryology of the Colon, Rectum, and Anus." In: Steele SR, et al. (eds.), The ASCRS Textbook of Colon and Rectal Surgery, 4th ed. Springer Nature Switzerland AG; 2022. pp. 3–27 (PDF pp. 20–44 of the combined textbook file). Source file: raw/ASCRS Textbook 4th Ed.pdf (full 1,198-page textbook; not split into per-chapter files — cite by page range within the single PDF).

Type: Specialty textbook chapter (reference/background, not primary literature) — but a step up in authority from the Sabiston chapters used elsewhere in this wiki, since this is the dedicated colorectal-surgery specialty reference (ASCRS) rather than a general-surgery textbook's colorectal chapters.

Scope

First chapter of a new, larger ingest: the full 4th edition ASCRS textbook (72 chapters across 6 parts — Perioperative/Endoscopy, Anorectal Disease, Malignant Disease, Benign Colorectal Disease, Pelvic Floor Disorders, Miscellaneous), being ingested sequentially front-to-back per Stephen's direction. This chapter covers gross anatomy of the anal canal, pelvic floor, rectum, and colon, plus GI embryology and congenital anomalies of the colon/rectum/anus.

Key content

Full synthesis written directly into the new concept page Colorectal Anatomy & Embryology rather than summarized twice here — see that page for anal canal definitions (anatomic vs surgical), sphincter complex anatomy, pelvic floor muscle anatomy/innervation, rectal anatomy (thirds, fascial planes, blood supply, rectal valves), anorectal spaces, colonic anatomy and blood supply (including the Griffiths'-point watershed and an accessory middle colic artery found in 36.4% of one series), and embryology (midgut rotation stages and anomalies, congenital colorectal/anorectal malformations).

Limitations

• Textbook chapter, not primary literature — cited figures (e.g., middle rectal artery presence 12–91% across studies, AMCA in 36.4% of one single-center series) are as reported by the chapter's authors from their own literature review, not independently re-verified against the original studies.
• Several genuinely disputed points are flagged as disputed by the chapter itself rather than resolved: whether lateral ligaments exist/what they contain, what "Waldeyer's fascia" actually refers to, and whether a true rectosigmoid sphincter exists.

Relevance

Opens the wiki's ingest of the ASCRS textbook — the specialty-specific reference this vault has been missing (everything so far has been either primary literature or the general-surgery Sabiston chapters). Creates the wiki's first dedicated colorectal/anorectal anatomy page (Colorectal Anatomy & Embryology), corroborates Meckel Diverticulum without contradiction, and flags one genuine measurement discrepancy with Rectal Cancer's Sabiston-sourced rectal-third boundaries. Sets up anatomic grounding for several chapters not yet ingested (hemorrhoids, cryptoglandular fistula/abscess, Hirschsprung's disease, pediatric anorectal malformations).