Rectum Flashcards Preview

Anatomy (TOPNOTCH SUPPLEMENT) > Rectum > Flashcards

Flashcards in Rectum Deck (15):
0

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

1

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

4

Venous drainage of the rectum

Superior rectal vein --> IMV --> portal vein

5

Autosomal dominant

Mutation in APC anti-oncogene, ras proto-oncogene, DCC anti-oncogene & p53 anti-oncogene

MC site: rectosigmoid colon

Familial adenomatous polyposis (FAP)

6

Adenomatous polyps + multiple osteomalacia

Gardner syndrome

7

Adenomatous polyps + gliomas

Turcot syndrome

8

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

9

IBD, always involve the rectum & extends proximally, no skip areas

May lead to toxic megacolon

Ulcerative colitis

10

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

11

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

12

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

13

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

14

+feces ➡️ pressure-sensitive receptors in ampulla of rectum

Motor:
- pelvic splanchnic nerve (parasympathetic, S2-4)
- ⬆️ peristalsis
- relax the internal anal sphincter

If external sphincter & puborectalis muscle are also relaxed ➡️ defecation

If external anal sphincter & puborectalis muscle are contracted ➡️ feces move back into sigmoid colon for storage
- HYPOGASTRIC PLEXUS & LUMBAR SPLANCHNIC NERVE amidsanal sphincter

Defection reflex