Rectum Flashcards
What is the rectum?
pelvic end of alimentary tract where feces accumulate prior to defecation
Where is the rectum located?
located between sigmoid colon and anal canal
Rectosigmoid junction located anterior to what?
S3
Is the rectum retro/intra/extra peritoneal?
retroperitoneal
Which structure expands into a continuous layer onto the rectum?
Teniae coli of sigmoid colon
Does the rectum have epiploic appendages, haustra, or sacculations?
no, they are absent
What is the sacral flexure?
rectum follows contour of sacrum and coccyx
What is the anorectal flexure?
shape turn at coccyx where rectum pierces pelvic diaphragm
What is approximate 80degree posterior turn of the anorectal flexure important for?
maintaining fecal continence (control of bowels)
What muscle maintains tonus of the anorectal flexure?
Puborectalis m.
- must actively contract to resist peristaltic contractions in rectum and prevent defecation
What needs to happen for conscious defecation to occur?
relaxation of puborectalis m.
what are the 3 sharp lateral flexures present in rectum and what do they correspond to?
Superior, intermediate and inferior
- correspond to Transverse rectal folds of the mucosa and submucosa
What is the ampulla of the rectum?
dilatable terminal region lying above and supported by levator ani m.
-Relaxes to hold accumulating fecal material prior to defecation
Yo, the superior 3rd of rectum is retroperitoneal and inferior 3rd is subperitoneal
random part in the notes…. guess there is no middle area
What structures provide space for rectum to distend as it fills with feces? (male vs. female)
Rectovesical pouch (male) Rectouterine pouch (females) Pararectal fossae
What forms the peritoneal reflection in males?
rectovesical pouch
What forms the peritoneal reflection in females?
rectouterine pouch
What forms as the lateral peritoneal reflection in both sexes?
Pararectal fossae
What structures are associated with rectum posteriorly? (both sexes)
- sacral vertebrae and coccyx
- sacral plexuses and inferior ends of sympathetic trunks
- median sacral a. and v.
What structures are associated with the rectum anteriorly for males?
-Fundus of urinary bladder and terminal parts of ureters
-Ductus deferens, seminal vesicles and prostate
(separated from these structures by rectovesical pouch)
What structures are associated with the rectum anteriorly for females?
Vagina, posterior fornix, and cervix of uterus
separated from these structures by rectouterine pouch
What is the arterial supply to rectum?
Superior rectal a.
Middle rectal a.
inferior rectal a.
Superior rectal a.
Branch from Inferior mesenteric a.
-supplies proximal part of sacrum
Middle rectal a.
Branches from internal iliac (anterior division)
Inferior rectal a.
Branches from internal pudendal a.
-supplies anorectal junction and anal canal
What is the venous drainage of the rectum?
Superior rectal v.
Middle rectal v.
Inferior rectal v.
Superior rectal v.
drains hepatic portal venous system
Middle and inferior rectal v.v.
drains to systemic system via internal iliac v.
-anastomoses b/t these veins create an important portacaval anastomosis
What are enlarged veins around the inferior rectum and anal canal?
Hemorrhoids
What are hemorrhoids?
Dilated and prolapsed veins of rectal venous plexus
What are predisposing factors of hemorrhoids?
those that cause increased intra-abdominal pressure
- E.g. pregnancy or chronic constipation
- Can occur in cases of portal hypertension (rectal v.v. are an anastomosis b/t portal and systemic system)
What are the types of hemorrhoids?
Internal or External
Internal hemorrhoids
probably due to breakdown of muscularis mucosa
-prolapse into lumen of anal canal and ulcerate (blood in stool)
External hemorrhoids
Involves external rectal venous plexus and are covered by skin
What is the superior lymphatic drainage of the rectum?
drains through pararectal to inferior mesenteric and lumbar nodes
What is the inferior lymphatic drainage of the rectum?
drains though internal iliac nodes
What is the sympathetic innervation of the rectum?
via lumbar splanchnic n. through superior hypogastric plexus
- Follow superior recta a. (branch of Inferior mesenteric a.)
- Possibly vasomotor but not functionally significant
What is the parasympathetic innervation of the rectum?
via pelvic splanchnic n. through inferior hypogastric plexus
-motor fibers to rectal muscularis externa
Visceral afferents pass retrogradely through what?
pelvic splanchnic n. S2-S4
-both pain and/or distention (indicating gas or feces)
What n. mediated innervation controls defecation?
pelvic splanchnic n.
What happens when ampulla is empty?
Internal anal sphincter m. contracted
External anal sphincter m. relaxed
What happens when feces accumulates in ampulla and sufficiently distends it?
Internal anal sphincter m. reflexively relaxes
External anal sphincter m. reflexively contracts
-Initiated by visceral afferents in pelvic splanchnic n.
What is required for defecation?
Requires voluntary override of reflexive external anal sphincter m. contraction
-Puborectalis m. also must voluntarily relax
What causes movement of feces?
Parasympathetic stimulation increases peristaltic activity in rectum
-movement assisted by increased abdominal pressure
Rectal examination, and what are you feeling for in males and females?
Provides opportunity to palpate many clinically significant structures
- Males: prostate and seminal vesicles
- Females: cervix
- Both: sacrum, coccyx, ischial spines and tuberositie
What pathologies are you looking for during a rectal exam?
enlarged nodes, thickened ureters or abscesses
What is used to visualize rectal lumen and remove lesions?
Proctoscope
