Faecal Continence Flashcards
requirements for control of excretion of faeces
a holding area
normal visceral afferent nerve fibres
functioning muscle sphincters
normal cerebral function
describe the holding area for control of excretion of faeces
the rectum;
stores faeces until appropriate to defecate
describe the normal visceral afferent nerve fibres for control of excretion of faeces
senses fullness of the rectum
describe the functioning muscle sphincters for control of excretion of faeces
respond to fullness of the rectum;
appropriately contract, preventing defecation
relax, allowing defecation
describe normal cerebral function for control of excretion of faeces
controls appropriate time t defecate
what can affect normal excretion of faeces
neurological pathology
medications
degeneration of nerve innervation of muscle (age-related)
consistency of stool (diarrhoea)
neurological pathology affecting normal excretion of faeces
dementia
stroke
MS
trauma (spina cord injury)
where is pelvic cavity located
within boy pelvis
continuous with abdominal cavity
between pelvic inlet and pelvic floor
what does pelvic cavity contain
pelvic organs and supporting tissues
rectum
what do openings in the pelvic floor permit
permits distal parts of alimentary, renal and reproductive tracts to pass from pelvic cavity into perineum
where does sigmoid colon become rectum
anterior to S3;
rectosigmoid junction
where does rectum become anal canal
anterior to tip of coccyx prior to passing through pelvic floor
where is anus located
distal end of anal canal
in the perineum
describe the anus
the orifice through which faeces pass
where is rectum located
in the pelvic
where is anal canal located
in the perineum
where does rectal ampulla lie
immediately superior to elevator ani muscle
role of the rectum
walls can relax - accommodating faecal material
functioning muscles and muscle sphincters required to hold faeces in ampulla until appropriate to defecate
what part of the rectum does the peritoneum cover
superior rectum
pouches of peritoneum
rectouterine (pouch of Douglas)
rectovesical
anatomical relationship between pouches of peritoneum and rectum
pouches lie anterior to superior rectum
anatomical relationship between prostate gland and rectum
prostate gland anterior to inferior rectum
anatomical relationship between vagina and cervix and rectum
vagina and cervix anterior to inferior/middle rectum
proper name for pelvic floor muscles
lavator ani msucles
what do pelvic floor muscles form
forms most of pelvic diaphragm - floor of pelvis and roof of perineum
together with fascial coverings
what is the pelvic floor made up of
a number of small skeletal muscles;
iliococcygeus
pubococcygeus
puborectalis
function of pelvic floor
provides continual support for pelvic organs - tonically contracted most of time
further contraction of pelvic floor
increases during an increase in intra-abdominal pressure (e.g. coughing, sneezing)
relaxation of pelvic floor
allows defecation and urination
nerve supply of pelvic floor
the nerve to levator ani
pudendal
describe the nerve of levator ani
branch of sacral plexus
describe the pudendal nerve
from S2, 3, 4
what is the puborectalis
part of levator ani muscle
skeletal muscle
role of puborectalis
maintains faecal continence
contraction of puborectalis
decreases anorectal angle- acting like a sphincter
helps maintain continence
describe the anal sphincters
2;
internal - smooth muscle
external - skeletal muscle
where is internal anal sphincter located
superior 2/3 of anal canal
how is contraction stimulated in internal anal sphincter
sympathetic nerves
how is contraction inhibited in internal anal sphincter
parasympathetic nerves - in response to distension of rectal ampulla
where is external anal canal sphincter located
inferior 2/3 of anal canal
superior part of sphincter continuous with puborectalis muscle
how is contraction stimulated in external anal sphincter
pudendal nerve - in repose to rectal ampulla distension and internal sphincter relaxation
where do sympathetic nerve fibres of rectum/anal canal leave the spinal cord
T12-L2
course of sympathetic nerve fibres of rectum/anal canal
synapse at inferior mesenteric ganglia
reach rectum via periarterial plexuses around branches of IMA
where do visceral afferents of rectum/anal canal leave spinal cord
S2-S4
visceral afferents of rectum/anal canal
run with parasympathetics
sense stretch
where do parasympathetic nerve fibres of rectum/anal canal leave spinal cord
S2-S4
course of parasympathetic nerve fibres of rectum/anal canal
leave spinal cord via splanchnic nerves
synapse in walls of rectum
function of parasympathetic nerve fibres of rectum/anal canal
inhibits internal anal sphincter
stimulates peristalsis
somatic motor nerve of rectum/anal canal
come from pudendal nerve (S2-S4) and nerve to levator ani (S3-S4)
function of somatic motor nerve of rectum/anal canal
contraction of external anal sphincter and puborectalis
what is the pudendal nerve a branch of
branch of sacral plexus
S2, S3, S4 anterior rami
what does the pudendal nerve supply
supplies external anal sphincter
how does pudendal nerve exit pelvis
via greater sciatic foramen
how does pudendal nerve enter perineum
via lesser sciatic foramen
branches of pudendal nerve
branches to supply structures of perineum
how can pudendal nerve/sphincter be damaged
during labour;
stretched
torn - weakened muscles
can cause faecal incontinence
what is the pectinate line
marks the junction between the part of the embryo which formed the GI tract (endoderm) and part that formed the skin (ectoderm)
arterial supply superior to pectinate line
from inferior mesenteric artery
venous drainage superior to pectinate line
to portal venous system (IMV)
nerve supply superior to pectinate line
autonomic
lymphatic drainage superior to pectinate line
inferior mesenteric nodes (internal iliac nodes)
arterial supply inferior to pectinate line
from internal iliac artery
venous drainage inferior to pectinate line
to systemic venous system (internal iliac)
nerve supply inferior to pectinate line
somatic
pudendal
lymphatic drainage inferior to pectinate line
superficial inguinal nodes
describe the lymphatics of the pelvis
lie alongside the arteries
what do internal iliac lymph nodes drain
inferior pelvic structures
what do external iliac lymph nodes drain
lower limb
superior pelvic structures
what do common iliac lymph nodes drain
lymph from external and internal iliac nodes then onto lumbar nodes
arterial supply of rectum and anal canal
internal iliac artery - degree of anastomoses
how do rectal varies form
in relation to portal hypertension
dilation of collateral veins between portal and systemic venous system
what are haemorrhoids
prolapses of rectal venous plexuses
how do haemorrhoids form
raised pressure (e.g. chronic constipation, training, pregnancy)
where are ischionanal fossae found
lie on each side of anal canal (left and right)
what are ischioanal fossae filled with
fat and loose connective tissue
how do the 2 ischionanal fossae communicate with each other
posteriorly
infeciton within ischioanal fossa
ischioanal abscess
