3- Faecal continence: the distal part of the GI tract Flashcards
what makes up the distal GI tract?
- rectum
- anal canal
- anus
what are paracolic gutters - why are they clinically important? where are they?
- para (beside) colic (colon) = beside the colon. sit between lateral edge of ascending and descending colon, and abdominal wall
- they’re part of greater sac of peritoneal cavity
- they’re significant as potential sites of excess blood/pus/fluid so when lying down one of the areas that you check for excess fluid (similar to hepatorenal recess and subphrenic recess)
what are the sacs of large intestine?
the bumps = haustra
which flexure of large intestine is more superior - hepatic or splenic flexure?
splenic flexure usually more superior than hepatic (because hepatic is lower due to presence of liver)
what are the smooth muscle bands in large intestine?
there are 3 distinct longitudinal bands of thickened smooth muscle running from caecum to distal end of sigmoid colon
what are normal things to see on abdominal x-ray?
- bubbles of air throughout colon
- mottled appearance of faeces mixing with air in rectum
what is holding area for faeces?
rectum
what nerves are for detecting when rectum is full?
picked up by sensory nerves and since rectum is viscera = visceral afferents
what can affect faecal continents?
- medication
- natural age related degeneration of nerve innervation of muscle
- consistency of stool
what are 2 parts of pelvic cavity?
lighter green = greater/false pelvis
darker green = true/lesser pelvis
is abdominal cavity and pelvic cavity seperate?
no - they’re contiunuous
what is pelvic inlet?
ring of bone by sacrum, ileum and pubic bone
what is purpose of pelvic cavity?
supports organs of pelvis, has lots of supporting (fatty, connective) tissue and is where rectum is located
what is pelvic floor the floor and roof of?
- floor of pelvis
- roof of perineum
what are openings in the pelvic floor?
alimentary, renal and reproductive tracts to pass from the pelvic cavity into the perineum
when does sigmoid colon become rectum?
rectosigmoid junction = anterior to S3
when does rectum become anal canal?
anterior to the tip of the coccyx just prior to passing through the levator ani muscle
what organs are in pelvis or perineum out of rectum, anal canal, anus?
- rectum in pelvis
- anal canal & anus in perineum
what is main part of rectum?
rectum ampulla (sac like enlargement)
→can enlarge in response to faces collecting in it →smooth muscle relaxes and allows filling, the muscles must also contract to defecate
what lies over the superior aspect of rectum?
peritoneum
what pouch lies anterior to superior rectum?
rectouterine in females (pouch of douglas)
rectovesical in males
where does prostate gland lie in relation to rectum?
prostate gland lies anterior to inferior rectum
where does vagina & cervix lie in relation to rectum?
vagina & cervix lies anterior to inferior/middle rectum
what is the levator ani muscles?
= means elevating/lifting anus (rectum)
- forms most of pelvic diaphragm
makes up 3 different muscles. skeletal muscles so under voluntary control
what are the 3 different muscles of levator ani muscle?
pubococcygeus = pubic & coccyx
ileococcygeus = ileum & coccyx
puborectalis = pubic & rectum →important one
what happens when levator ani muscle relaxes/contracts?
levator ani muscles are always a bit contracted (tonic) to provide support to organs of pelvic
what nerve supplies the levator ani muscles?
pudendal s2,3,4
s2,3,4 keeps the anus on the floor
what is the anorectal angle?
between anal canal and rectum
what is puborectalis function when contracting?
puborectalis is one of the levator ani muscles
= when contracting pulls anal rectal angle towards pubic bone (decreases angle) which means less room internally for any faeces to go through →so kinda acts like a sphincter (NOT A SPHINCTER) - stops defecating if you want to (under control)
what are the 2 anal sphincters?
- 1 internal smooth muscle = involuntary control
- 1 external skeletal muscle = voluntary control
what supplies the internal anal sphincter? and what is it composed of?
- it’ composed of smooth muscle (involuntary)
- contraction is stimulated by sympathetic nerves (sphincter closed)
- contraction is inhibited by parasympathetic nerves
= it’s contracted all the time, relaxes reflexively in response to distension (filling) of rectal ampulla
what supplies the external anal sphincter? and what is it composed of?
- skeletal muscle (voluntary)
- contraction is stimulated by the pudendal nerve (because in perineum) →contract voluntarily in response to ampulla filling up and internal one relaxes -external one cause wait not appropriate time right now
when does external anal sphincter contract?
voluntarily contracted (along with puborectalis muscle) in response to rectal ampulla distension and internal sphincter relaxation
where is
a) external anal sphincter?
b) internal anal sphincter?
a) superior two thirds of anal canal
b) inferior two thirds of anal canal (superior part of the sphincter is continuous with the puborectalis muscle)
= they overlap
what control are organs in pelvis under?
autonomic control
what control are organs in perineum under?
part of body wall →somatic, under voluntary control (somatic motor, somatic sensory)
what type of pain is in pelvis?
part of viscera so dull & achy
what type of pain is in perineum?
part of body wall so sharp, stabbing, well localised
what is nerve supply is above levator ani?
above levator ani = in pelvic cavity
sympathetic supply = thoracolumbar - sympathetic motor is T12-L2 to supply rectum
parasympathetic supply = craniosacral - s2,3,4 (same level as pudendal nerve but not part of pudendal nerve)
what nerves run from s2,3,4 level?
- visceral afferents
- parasympathetic
- pudendal
what nerves run from T12-L2 level?
sympathetic motor
what is pudendal nerve?
branch of sacral plexus that comes from S2, S3, S4 anterior rami and supplies external anal sphincter
what is route of pudendal nerve?
from S2, S3, S4 anterior rami and exits pelvis via greater sciatic foramen then quickly enters perineum via lesser sciatic foramen and branches to supply structures of perineum
what are ways pudendum can be damaged in labour?
- the branches of the pudendal nerve could be stretched →resultant stretch of the nerve fibres
- fibres within the puborectalis or external anal sphincter muscle could be torn →results in weakened muscle
- faecal incontinence could result
what is pectinate line?
junction formed between the part of the embryo which formed the GI tract (endoderm) and the part that formed the skin (ectoderm)
= everything above is visceral and everything below is parietal (means different blood supplies etc on either side of line)
for above pectinate line, what is
a) nerve supply
b) anterior supply
c) venous drainage
d) lymphatic drainage
above = visceral
a) autonomic
b) inferior mesenteric artery
c) to portal venous system
d) inferior mesenteric nodes (internal iliac nodes)
for below pectinate line, what is
a) nerve supply
b) anterior supply
c) venous drainage
d) lymphatic drainage
below = perineum
a) somatic and pudendal
b) internal iliac artery
c) to systemic venous system via internal iliac
d) superficial inguinal nodes
where are lymph vessels of pelvic?
lymph vessels tend to lie alongside arteries
what are the main groups of lymph nodes draining the pelvic organs?
- internal iliac (draining inferior pelvic structures)
- external iliac (draining lower limb, and more superior pelvic structures)
- common iliac (drain the lymph from the external and internal iliac nodes)
- lymph draining through the common iliac nodes then drains to the lumbar nodes
what artery supplies the hindgut organs?
inferior mesenteric artery
what level of anal canal has what artery?
proximal half (up to pectinate line) is part of hindgut so inferior mesenteric artery
- the rest of GI tract is supplied by internal iliac artery
when do rectal varices form?
relation to portal hypertension
- dilation of collateral veins between portal and systemic venous systems
when do hemorrhoids form?
= are prolapses of the rectal venous plexuses
- their development is not related to portal hypertension
- raised pressure e.g. chronic constipation, straining, pregnancy
what is ischioanal fossa?
space on either side of anal canal (between ischium & anal canal)
= it’s filled with fat & loose connective tissue allowing rectum & anal canal to expand into fatty area without effecting anything else important
what is an infection of ischioanal fossa called?
ischioanal abscesses
what can happen to ischioanal fossa if malnourished?
they can lose fatty pads in ischial, more prone to prolapse
what is assessed in digital rectal examination?
- “assess anal tone”: the effectiveness/strength of the external anal sphincter
- in the male, palpate the prostate anteriorly
- in the female, palpate the cervix
what is proctoscopy?
viewing the interior of the rectum
what is sigmoidoscopy?
viewing the interior of the sigmoid colon
what is colonoscopy?
viewing the interior of the colon
