Flashcards in Rectum Deck (15):
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Begins at S3, ends at the tip of coccyx (anorectal junction), where puborectalis muscle forms s U-shaped sling that causes a 90% perineal flexure
Rectum
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Just above the pelvic diaphragm, generate the urge to defecate
Ampulla of rectum
2
Contains 3 transverse rectal folds (Houston valves)
Mucosa
Submucosa
Inner circular layer of smooth muscle
3
Blood supply of rectus
Inferior mesenteric artery via the superior rectal artery
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Venous drainage of the rectum
Superior rectal vein --> IMV --> portal vein
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Autosomal dominant
Mutation in APC anti-oncogene, ras proto-oncogene, DCC anti-oncogene & p53 anti-oncogene
MC site: rectosigmoid colon
Familial adenomatous polyposis (FAP)
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Adenomatous polyps + multiple osteomalacia
Gardner syndrome
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Adenomatous polyps + gliomas
Turcot syndrome
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Mutations on HNPCC gene
R sided tumors - iron deficiency anemia
L sided tumors - obstruction & bloody stools
MC site of metastasis: liver because sigmoid vein & superior rectal vein drain into portal system
Posterior mets may involve the sacral nerve plexus --> sciatica
Colonic adenocarcinoma
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IBD, always involve the rectum & extends proximally, no skip areas
May lead to toxic megacolon
Ulcerative colitis
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Protrusion of full thickness of rectum through the anus (vs mucosal prolapse which is the protrusion of just the rectal mucosa)
Anal incontinence (stretching of internal & external sphincters or stretch injury to pudendal nerve
Rectal prolapse
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Divided into upper & lower portion by the Pectinate line
Surrounded by 2 sphincters:
- internal anal sphincter (smooth muscle, involuntary, via autonomic innervation)
- external anal sphincter (striated muscle, voluntary, via pudendal nerve)
Upper anal canal mucosa extends into longitudinal folds (anal column, columns of Morgagni)
- Pectinate lime is defined by the base of anal columns
- anal valves are found at the base of anal columns
- behind the anal valves are anal sinuses into which anal glands open
Anal canal
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Location: from anorectal junction (perineal flexure to Pectinate line)
Blood supply: superior rectal artery
Venous drainage: superior rectal vein ➡️ IMV ➡️ portal system
Lymphatic drainage: deep nodes
Innervations:
- motor: autonomic for internal anal sphincter
- sensory: stretch only, no pain sensation
Embryonic derivation: endoderm (hindgut)
Epithelium: simple columnar
Tumors: no palpable enlarged superficial nodes, no pain
Hemorrhoids:
- internal (varicosities of superior rectal veins)
- covered by rectal mucosa
- no pain
Upper anal canal
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Location: from Pectinate line to anal verge
Blood supply: inferior rectal artery (branch of internal pudendal artery)
Venous drainage: inferior rectal vein ➡️ internal pudendal vein ➡️ internal iliac vein ➡️ IVC
Lymphatic drainage: superficial inguinal nodes
Innervations:
- motor: somatic (pudendal nerve) for external anal sphincter
- sensory: pain, temp, touch
Embryonic derivation: ectoderm (proctodeum)
Epithelium: stratified squamous
Tumors:
- palpable enlarged superficial nodes
- +pain
Hemorrhoids:
- external (varicosities of inferior rectal veins)
- covered by skin
- +pain
Lower anal canal
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