Clinical Anatomy of Faecal Continence Flashcards
distal GI tract
colon
rectum
anal canal
anus
function is to excrete stool
control of the excretion of faeces
holding area - rectum
normal visceral afferent nerve fibres to sense fullness
functioning muscle sphincters around distal end
appropriate contraction to avoid defection and to relax
normal cerebral function to control the appropriate time to defecate
affected by neurological pathology
factors which affect faecal continenece
medications
natural age-related degeneration of nerve innervation
consistency of stool
pelvic cavity
continuous with abdominal cavity above
lies between pelvic inlet and pelvic floor
contains pelvic organs and supporting tissues
levator ani muscle = pelvic floor
forms the musculofascial inferior part of the pelvic cavity
pelvic floor
openings in the pelvic floor permit the distal parts of alimentary, renal and reproductive tracts to pass from the pelvic cavity into the perineum
distal GI tract within the pelvis and perineum
sigmoid colon becomes rectum anterior to S3 - recto-sigmoid junction
rectum becomes anal canal anterior to the tip of the coccyx just prior to passing through the levator ani muscle
anus is the distal end of the anal canal and is the orifice through which faeces pass
rectum is in the pelvis and the anal canal and anus are in the perineum
rectum
rectal ampulla lies immediately superior to the elevator ani muscle
walls can relax to accommodate faecal material
sphincters required
MALE
between bladder and rectum
rectovesical pouch
FEMALES
between bladder and uterus
vesicouterine pouch
FEMALES
between uterus and rectum
rectouterine pouch of Douglas
levator ani muscle
made up of a number of smaller muscles - pubococcygeus, puborectalis, iliococcygeus
skeletal muscle
forms floor of pelvis and roof of perineum
tonically contracted most of the time
reflexively contracts further during increase in intra-abdominal pressure (coughing, sneezing)
supplies by branch of the sacral plexus and pudendal (S2, 3, 4)
puborectalis
maintaining faecal continence
contraction - decreases anorectal angle
acts like a sphincter
skeletal muscle (voluntary)
anal sphincters
internal - smooth muscle superior 2/3 of anal canal stimulated by sympathetic nerves inhibited by parasympathetic nerves contracted all the time
external - skeletal
inferior 2/3 od anal canal
stimulated by pudendal nerve
voluntarily contracted
nerve supply in pelvis
body cavity
sympathetic, parasympathetic and visceral afferent
nerve supply in perineum
body wall
somatic motor and somatic sensory
nerve supply to rectum/anal canal
sympathetic fibres = T12-L2
visceral afferents = S2-S4
parasympathetic fibres = S2-S4
somatic motor = S2,3,4
pudendal nerve
branch of sacral plexus
S2,3,4 anterior rami
supplies external anal sphincter
sciatic foramen
damage to pudendal nerve or sphincter
LABOUR
branches of the pudendal nerve could be stretched
fibres within the puborectalis or external anal sphincter muscle could be torn
results in weakened muscle and may lead to faecal incontinence
anal canal - pectinate line
marks the junction between the part of the embryo which formed the GI tract and the part that formed the skin
superior = visceral inferior = parietal
above pectinate line
autonomic
arterial supply = inferior mesenteric artery
venous drainage = hepatic portal system
lymphatic drainage = inferior mesenteric nodes
below pectinate line
somatic and pudendal
arterial supply = interval ilicc artery
venous drainage = systemic venous system
lymphatic drainage = superficial inguinal nodes
lymphatics of the pelvis
lymph vessels tend to lie alongside the arteries
interla iliac - inferior structures
external iliac - lower limbs and superior structure
common iliac - external and internal iliac nodes
common iliac nodes then drains to the lumbar nodes
blood supply to rectum and anal canal
inferior mesenteric artery supplies the handgun organs (proximal half of the anal canal)
interal iliac artery
degree of anastomoses between these vessels
