Relations
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Peritoneum
Upper third of rectum covered by peritoneum on anterior aspect and sides
Middle third of rectum covered by peritoneum on anterior surface only
Lower third of rectum below peritoneal reflection
Pararectal fossae on lateral sides of rectum in peritoneal cavity
Rectovesical septum of pelvic fascia separates rectum from prostate
Rectovaginal septum of pelvic fascia separates rectum from vagina
Lateral ligaments of rectum-condensations of pelvic fascia around middle rectal vesselsRelations of Rectum
Relations
Posterior Sacrum
Coccyx
Piriformis muscle
Superior rectal vessels
Hypogastric plexus (ANS)
Sympathetic trunk nerves
Sacral plexus
Inferior Levator ani muscles
Lateral Pelvic plexus nerves (ANS)
Ureters
Anterior Sigmoid colon
Ileum
Anterior structures palpable on rectal examination Prostate (males)
Base bladder
Seminal vesicles (males)
Ampullae of ductus deferens (males)
Cervix (females)Blood supply
Arterial
Mainly by superior rectal artery (continuation of inferior mesenteric artery)
Also supplied by the middle rectal arteries (from internal iliac arteries) to the middle and inferior parts
Inferior rectal arteries supply the anorectal junctions and anal canal
Superior, middle, and inferior rectal arteries anastomose with each other
Venous
Chief drainage via a rectal venous plexus to the superior rectal vein
Middle and inferior rectal veins also drain the rectum
Superior rectal vein drains to the portal system
Middle and inferior rectal veins drain to the inferior vena cava via the internal iliac vein
Anastomoses between these veins link the portal and system systems
Lymphatic drainage
Lymphatic vessels from superior half of rectum drain to pararectal nodes and from there to inferior mesenteric and lumbar nodes
Lymphatic vessels from the inferior half of the rectum travel with the middle rectal vessels to the internal iliac nodes and
anastomose with the lymphatics of the anal canal
Nerve supply
Sympathetic innervation
From lumbar sympathetic fibers via the inferior mesenteric arteries and the superior rectal arteries to the superior rectal plexus to
blood vessels of rectum
Parasympathetic innervation
Are the main motor fibers to muscles of the rectal wall
From the pelvic splanchnic nerves (S2-S4) via the inferior hypogastric (pelvic) plexus to middle rectal plexus
Visceral afferent (sensory) fibers travel via the inferior hypogastric (pelvic)
plexus and pelvic splanchnics back to spinal cordpage 200
page 201Anal Canal
Gross structure
Terminal part of gastrointestinal tract
Is approximately 3 cm long
Commences at anorectal junction and ends at anus
Encircled by internal and external sphincter muscles
Descends between perineal body and anococcygeal ligament
Mucosal lining of superior has longitudinal ridges-anal columns
Inferior ends of columns joined by anal valves
Behind valves are small sinuses: anal sinuses
Anal glands (mucus) empty into anal sinuses
Inferior end of anal valves forms an irregular line: pectinate (or dentate) line
Pectinate line divides the superior portion of the anal canal, derived from embryonic endoderm (hindgut), from the inferior portion derived
from ectoderm (proctodeum)