Clinical anatomy of faecal continence Flashcards
what are the functions of the rectum, anal canal and anus?
= to excrete stool
what is the holding area of stored faeces called before it is fefecated?
the rectum
what senses ‘fullness’ of the rectum?
what responds to the fullness?
= normal visceral afferents nerve fibres
Response
= functioning muscle sphincters around the distal end of the GI tract
what do the sphincters do to allow defeceation?
= to allow contraction, preventing defeceation and to relax allowing defeceation
what controls the appropriate time to defecate?
= normal cerebral function
what can all of the normal visceral afferent nerve fibres, normal cerebral function e.t.c be affected by?
neurological pathology
e.g. stroke, dementia, stroke, MS, trauma
how else can faecal continence be affected? (3)
1) by medications
2) by natural age related degeneration of nerve innervation of muscle
3) by consistency of stool
where dos the pelvic cavity lie?
= bony pelvis
what is the pelvic cavity continuous with?
abdominal cavity above
what does the pelvic cavity lie between?
= pelvic inlet and pelvic floor
what does the pelvic cavity contain?
= pelvic organs and supporting tissue
where is the rectum located?
= within pelvic cavity
what does openings in the pelvic floor permit?
= permits the distal parts of alimentary, renal and reproductive tracts to pass from pelvic cavity into the perineum
what must pass trough the pelvic floor?
= rectum/anal canal
when does the sigmoidal colon become rectum?
= anterior to S3
“recto-sigmoidal junctions:
when does the rectum become the anal canal?
= anterior to the tip of coccyx just prior to passing through the elevator ani muscle
describe the anus.
= distal end of the anal canal and is the orifice through with faeces pass
where is the rectum, anal canal and anus located?
Rectum
= pelvis
Anal canal and anus
= perineum
where does the rectal ampulla lie?
= immediately superior to elevator ani muscle
why do the rectal walls relax?
= two accommodate faecal material
why are functioning muscles and muscle sphincters required?
= to hold faeces in the ampulla until appropriate to defecate
what does the peritoneum cover?
= the superior rectum
where does the Rectouterine/rectovesical pouch lie?
= anterior to superior rectum
describe the location of the rectum in male and female anatomy?
Male
= prostate gland lies anterior to inferior rectum
female
= the vagina and cervix lies anterior to inferior/middle rectum
what do the levator ani muscles form?
= most of pelvic diaphragm together with fascial coverings
Forms
- most of floor of pelvis
- forms most of roof of perineum
what is the levator ani muscles made up of?
= a number of smaller muscles
- puborectalis
- pubococygeus
- iliococcygeus
what sort of muscle is levator ani muscles?
= skeletal muscle
what do levator ani muscles provide?
= continual support for the pelvis organs - tonically contracted most of the time
- reflexively contracts further during increase in intra-abdominal pressure e.g. coughing or sneezing
- the muscles relax to allow defecation (& urinnation) to occur
what is the levator ani muscles supplied by?
= nerve to levator ani (a branch of the sacral plexus) & pudendal (S2, 3, 4)
what does contraction of puborectalis result in?
= decreases anorectal angles, acting like a sphincter
what is puborectalis controlled by?
= skeletal muscles; contraction is under voluntary control
describe what happens when the rectal ampulla is relaxed and filled with faecees and then voluntary contraction occurs?
= voluntary contraction of this muscle will helps maintain continence
describe the location of anal canal and anorectal junction.
anal canal is below the anorectal junction
what are the 2 anal sphincters?
1 internal sphincter (smooth muscle)
- superior 2/3rds of anal canal
- contraction stimulated by sympathetic nerves
- contraction is inhibited by parasympathetic nerves
- contracted all the time, relaxes reflexively in response to distension of renal ampulla
1 external sphincter (skeletal muscle)
- inferior 2/3rds of anal canal
- contraction stimulated by pudenal nerves
- voluntary contracted in response to renal ampulla distension and internal sphincter relaxation
why is the nerve supply fundamental?
= fundamental to dividing which nerve fibre types are carrying out with function
what are the structures in pelvis and perineum?
Pelvis;
- body cavity
- sympathetic, para-sympathetic and visceral afferents
Perineum
- body wall
- somatic motor and somatic sensory
where does the sympathetic fibres run from?
T12-L2
- travels from inferior mesenteric ganglia - synapse- then travel via peri-arterial plexuses around branches of IMA
= contraction of internal anal sphincter
= inhibits peristalsis
where do the parasympathetic fibres run from?
S2-S4
- via pelvic splanchnic nerves, synapse in walls of rectum
= inhibits internal anal sphincter
= stimulates peristalsis
describe the visceral afferents and somatic motor?
Viceral afferents;
- back to S2-S4
= run with parasympathetics
= sense stretch, ischaemia
Somatic motor;
- from pudendal nerve (S2-S4) and nerve to elevator ani (S3-S4)
= contraction of external anal sphincter and puborectalis
describe the pudendal nerve?
= branch of sacral plexus
- S2, S3, S4 anterior rami
= supplies external anal sphincter
= exits pelvis via greater sciatic foramen
= quickly enters perineum via lesser sciatic foramen
- branches to supply structure of perineum
what does the tear of perineum result in?
= tear extends posteriorly to involve the external anal sphincter
describe what happens during labour?
= branches of pudendal nerve could be stretched
- fibres within the pubo-rectalis or external anal sphincter muscle could be torn
- results in weakened muscle and lead to faecal in-continence
what line is the anal Canal on?
= pectinate line
- marks the junction between part of embryo which formed the GI tract (endoderm) and part that formed the skin (endoderm)
True or False.
Arterial supply, venous drainage, lymphatic drainage and nerve supply differ above and below pectinate line.
True
Superior to line = visceral
Inferior to line = pariettal
what is above the pectinate line?
Nerve supply = autonomic
Arterial supply = from inferior mesenteric artery
Venous drainage = to hepatic portal system
Lymphatic drainage = inferior mesenteric nodes
what is below the pectinate line?
Nerve supply = somatic and pudendal
Arterial supply = from internal iliac artery
Venous drainage = to systemic venous system
Lymphatic drainage = superficial inguinal nodes
what are the 4 main groups of lymph nodes gaining the pelvic organs?
1) Internal iliac (draining inferior pelvic structures)
2) External iliac (draining lower limb, and more superior pelvic structures)
3) Common iliac (drain the lymph from the external and internal iliac nodes)
4) Lymph draining through the common iliac nodes then drains to the lumbar nodes
what does the inferior mesenteric artery supply and what is the remainder of GI tract supplied by?
= the hindgut organs
- hindgut extends to proximal half of the anal canal (the pectinate line)
Remainder;
= supplied by internal iliac artery
- there is a degree of anastomoses between these vessels
what drains the hindgut organs?
= inferior mesenteric veins
- above pectinate line
- portal venous system
what vein drains below the pectinate line? (systemic venous system)
= internal iliac vein
when do rectal varices from?
= in relation to porttal hypertension
- distension of collateral veins between portal and systemic venous system
what are haemorrhoids?
= prolapses of rectal venous plexuses
- their development is NOT related to portal hypertension
- i.e. raised pressure e.g. chronic constipation, straining, pregnancy
where does the ischioanal fossa lie?
= on each side of anal canal
what is the ischioanal fossa filled with?
= fat and loose connective tissue
how do the two ischioanal fossa communicate with each other?
= posteriorly
what is an infection within the ischioanal fossa called?
= ischioanal abscess
what is proctoscopy, sigmoidoscopy and colonoscopy?
Proctoscopy
= viewing interior of rectum
Sigmoidoscopy
= viewing interior of sigmoid colon
Colonoscopy
= viewing the interior of colon
