Anatomy- Faecal Continence Flashcards
what is the role of the rectum
a holding area to store faeces until appropriate to defecate
what senses the fullness (stretching) of the rectum
normal visceral afferent nerve fibres
what can affect faecal continence
neurological pathology, medications, old age degeneration of nerve innervation of muscle, consistency of stool
what does the pelvic cavity lie within
the bony pelvis- between the pelvic inlet and pelvic floor
what is the pelvic cavity continuous with
abdominal cavity
what separates the abdominal cavity and the pelvic cavity
peritonium
what does the pelvic cavity contain
pelvic organs and supporting tissues- inc rectum
what muscle is known as the pelvic floor
levator ani
what do openings in the levator ani allow
distal parts of the alimentary, renal and reproductive tracts to pass from the pelvic cavity to the perineum
at what vertebrae does the sigmoid colon become the rectum
anterior to S3 (recto-sigmoid junction)
where does the rectum become the anal canal
anterior to the coccyx just prior to passing through the levator ani muscle
are the rectim, anal canal and anus in the pelvis or perineum
rectum in pelvis
anal canal and anus in the perineum
what is the difference between sigmoid and rectum
looses tinae coli and has longitundinal muscle fibres
where is the rectal ampulla
lies immediately superior to the levator ani muscle
why does the rectum have three folds
create staggering effect, allow for expansion
what part of rectum in under conscious control
the sphincters
what covers the superior rectum
peritoneum
what lies anterior to the superior rectum
rectouterine (pouch of douglas) /retrovesical pouch
what lies anterior to the inferior rectum in males
prostate
what lies anterior to the middle/inferior rectum in females
the vagina
what type of muscles make up the levator ani
skeletal- controlled consciously
where does the puborectalis go between
both pubic bones- most medial
where does the pubococcygeus go between
from pubic bone to coccyx
where does the illiococcygeus go between
inner side of ischium to coccyx
what muscles makes up the levator ani
puborectalis
illiococcygeus
pubococcygeus
when does the levator ani reflexively contract
during increased intra-abdominal pressure (coughing sneezing)
what innervates the levator ani
‘nerve to levator ani’ (branch of sacral plexus) and pudenal (main nerve of perineum) S2,3,4 (keeps the poo off the floor)
what does the pubrorectalis do to maintain faecal continence
acts like a sphincter by contracting and decreasing the anorectal angle (skeletal so under voluntary control)
what are the two anal sphincters
interal (smooth muscle) and external (skeletal)
what stimulates the internal anal sphincter to contract
sympathetic stimulation
where is the internal anal sphincter
superior two thrids
contraction of the internal anal is inhibited by what
parasympathetic nerves
when is the internal anal sphincter normally contracted and relaxed
contracted all the time- relaxes reflexively in response to distension (filling) of the rectal ampulla
where is the external anal sphincter
inferior two thirds of the anal canal (superior part continuous with the puborectalis muscle)
what stomulates the external anal sphincter to contract
pudendal nerve
when does the external anal sphincter voluntarily contract
in response to rectal ampulla distention and internal sphincter relaxation
what separates the pelvis from the perineum
the levator ani- above pelvis, below perineum
what type of nerves supply structures in the pelvis
body cavity- sympathetic, parasympathetic, visceral afferent
what type of nerves supply structures in the perineum
body wall- somatic motor and sensory
what are the important spinal chord levels for nerve supply to the rectum/ anal canal
T12-L2 and S2-4
what is the path and role of the sympathetic fibres from T12- L2
travel to inferior mesenteric ganaglia- synapse- then travel via parietal plexus around branches of the IMA
- contraction of internal anal sphincters
- inhibit peristalsis
what is the path and role of the visceral afferent coming back to S2-4
run with the parasympathetics
-sense stretch, ischaemia etc
what is the path and role of the parasympathetic fibres from S2-4
via pelvic splanchnic nerves, synapse in walls of rectum
- inhibit internal anal sphincter
- stimulate peristalsis
what is the role of the somatic motor from pudendal nerve S2-4 and nerve to levator ani
contraction of external anal sphincter and puborectalis
what is the pudendal nerve a branch of
the sacral plexus
what anterior ramis makes up the pudendal nerve
S2,3,4
via what does the pudendal nerve exit the pelvis
greater sciatic foramen
how does the pudendal nerve enter the perineum
via lesser sciatic foramen
what damage could result to loss of pelvic control during labour
tear of perineum, stretch of pudendal nerve, tear of puborectalis or external anal sphincter muscle fibres
what is the pectinate line
marks the junction between the part of the embryo that formed the GI tract (endoderm) and the part that formed the skin (ectoderm)
what changes when you cross the pectinate line
arterial supply, venous drainage, nerve supply, lymphatic drainage (superior= visceral inferior = parietal)
describe the nerve supply above and below the pectinate line
above- autonomic
below- somatic and pudendal
describe the arterial supply above and below the pectinate line
above- from IMA
below- from internal iliac artery
describe the venous drainage above and below the pectinate line
above- to hepatic portal sysetm (via IMV)
below- to systemic venous system (internal iliac)
describe the lymphatic drainage above and below the pectinate line
above- inferior mesenteric nodes (internal iliac nodes)
below- superficial inguinal nodes
why may cancer above the pectinate line not be felt
as visceral sensory only
where do lymph vessels tend to lie
alongside the arteries
what are the main groups of lymph nodes draining the pelvic organs and what does each drain
internal iliacs- inferior pelvic structures
external iliacs- lower limb, more superior pelvic structures
common iliac- drains external and interbal iliac nodes
lumbar nodes- lymph from common iliac nodes then goes to here
what artery supply with hindgut organs
IMA
what is the hindgut
distal 1/3rd of the transverse colon to proximal ½ of the anal canal (the ½ superior to the pectinate line)
what supplies the GI past the pectinate line (past the hindgut)
internal iliac artery (branches into middle and inferior rectal artery)
what vein drains the hindgut organs
superior rectal vein-
IMV- portal venous system
what vein drains below the pectinate line
middle and inferior rectal vein- internal iliac vein-
systemic venous system
when do rectal varices from
when there is portal hypertension- dilatation of collateral veins between portal and systemic systems
what are haemorrhoids and what causes them
prolapses of the rectal venous plexuses- NOT RELATED TO PORTAL HYPERTENSION- but caused by raised pressure (chronic hypertension, straining, pregnancy)
where are the ischioanal fossae
lie on either side of the anal canal
what are the ischioanal fossae filled with
fat and loose connective tissue
where do the ischioanal foscae communicate
posteriorly
what in an ischioanal abscess
an infection within the ischioanal fossa
what do you assess in an digital rectal exam
anal tone- strength/ effectiveness of the anal sphincter
palpate the prostate/ cervix
what is a proctoscopy
viewing the interior of the rectum
what is a sigmoidoscopy
viewing the interior of the sigmoid colon
what is a colonoscopy
viewing the interior of the colon
