9G. Anatomy of faecal continence Flashcards
what makes up the large intestine
caecum, appendix, colon (ascending, transverse, descending and sigmoid)
which is more superior to the other in terms of flexures
splenic flexure lies more superiorly than the hepatic flexure
what is the name of the longitudinal bands of thickened smooth muscle running from caecum to distal end of sigmoid colon
teniae coli
what is formed by tonic contraction of the teniae coli
haustra
what if you can see air in the ascending colon in the X ray
that is normal
what is used as contrast in imaging the GI system
Barium
how many paracolic gutters are there and name them
2 and they are Left and right
where are the paracolic gutters
between the lateral edge of ascending and descending colon, and abdominal wall
is the paracolic gutters part of the greater sac or the lesser sac
greater
what are the paracolic gutters susceptible to
collecting blood/pus
what 4 things do you need to control excretion of faeces and why
- holding area - rectum
- visceral afferent nerve fibres-to sense fullness of rectum
- functioning muscle sphincters-to contract and relax
4.cerebrum- to control the appropriate time to defecate
faecal continence is affected by what
medications, natural age related degeneration of nerve innervation of muscle
neural pathology - stroke, MS, Dementia, trauma (childbirth, spinal cord injury)
where is the pelvic cavity
within bony pelvis
between pelvic inlet and pelvic floor
what part of the GI system is located withing the pelvic cavity
rectum
what is the scienctific name for the pelvic floor
levator ani muscle
what gets let through the pelvic floor
openings in pelvic floor allow
uterus, neck of bladder and alimentary to pass from the pelvic cavity into the perineum
what is levator ani muscle
pelvic floor
when does the sigmoid colon become the rectum (and what’s its name)
anterior to S3
the rectosigmoid junction
when does the rectum become anal canal
anterior to the tip of the coccyx just prior to the passing through the levator ani muscle
what is the distal end of anal canal called
anus
so where is the rectum/anal canal/anus in terms of perineum/pelvis
rectum is in pelvis and anal canal and anus are perineum
what lies immediately superior to the levator ani muscle
rectal ampulla
what is the rectal ampulla
The rectal ampulla is the dilated (wider) section of the rectum, located just above the anal canal. (its walls can relax)
what keeps the faeces in the ampulla
functioning muscles and muscle sphincters
what covers the superior rectum
peritoneum
what is the pouch called that lies anterior to the superior rectum in men
rectovesicle pouch
what is the pouch called that lies anterior to the superior rectum in women
rectouterine pouch
what is the pouch called that lies between the bladder and uterus
vesicouterine pouch
what lies anterior to the inferior rectum
in men its prostate gland in women its vagina and cervix
what do the levator ani muscles do (forms)
forms most of pelvic floor and roof of perineum
forms most of pelvic diaphragm - together with fascial coverings
what kind of muscle is levator ani muscles
skeletal
what are the names of the smaller muscles making up the levator ani muscle
iliococcygeus
pubocoocygeus
puborectalis
are the levator ani muscles relaxed or contracted most of the time
contracted
when do the levator ani muscles contract further
due to an increase in intra-abdominal pressure like coughing or sneezing
when do the levator ani muscles relax
defecation and urination
the ‘nerve to levator ani’ is a branch of what
sacral plexus
what nerves supplies levator ani muscles
the ‘nerve to levator ani’
and
Pudendal (S2,3,4)
is skeletal muscle voluntary or involuntary
voluntary
which muscle decreases the anorectal angle when it contracts
puborectalis
when the puborectalis contracts what happens
decreases the anorectal angle and acts as a sphincter
how many sphincters in anal canal
2
describe the 2 sphincters of anal canal
1 is internal - smooth muscle
1 is external - skeletal muscle
where is the anal canal (what is it below)
ano-rectal junction
contraction of the internal anal sphincter is stimulated by what nerves
sympathetic
contraction of internal anal sphincter is inhibited by what nerves
parasympathetic
contraction of external anal sphincter is stimulated by what nerve
pudendal nerve
what nerves if the structure is in the pelvis and is body cavity
sympathetic, parasympathetic and visceral afferent
what nerves if the structure is in perineum and body wall
somatic motor and somatic sensory
what is the route of sympathetic fibres to inhibit peristalsis and contract anal sphincter internal
T12-L2 release sympathetic fibres - travels to inferior mesenteric artery annd synapse - travel along the periarterial pexuses around the IMA
what is the course for parasympathetic nerve fibres to stimulate peristalsis and relax anal internal sphincter
from S2 to S4 via pelvic spanchnic nerves to the walls in rectum
what nerve supplies the external anal sphincter
pudendal nerve
what rami is the pudendal nerve on
S2 S3 S4 ANTERIOR
where does the pudendal nerve exit in the pelvis
the greater sciatic foramen
where does the pudendal nerve enter in the perineum
the lesser sciatic foramen
when do you get pudendal or sphincter damage
during labour
why is there pudendal nerve damage or sphincter damage during labour
branches of pudendal nerve could be stretched
fibres within the puborectalis or external anal sphincter muscle could be torn leading to weakened muscle
this could result in faecal incontinence
what is the pectinate line
marks the junction between the part of the embryo which formed the GI tract (endoderm) and the part that formed the skin (ectoderm)
Arterial supply, venous drainage, lymphatic drainage and nerve supply differ above and below pectinate line
Superior to line = visceral
Inferior to line = parietal
what is the line called which marks the junction between the part of the embryo which formed the GI tract (endoderm) and the part that formed the skin (ectoderm) and tells you that the arterial supply, venous drainage and lymphatic drainage differs above or below it
pecinate
Arterial supply, venous drainage, lymphatic drainage and nerve supply differ above and below pectinate line. which is Superior which is inferior to the line
superior to the line is visceral and inferior to the line is parietal
describe the vessels above the pectinate line
nerve - autonomic
arterial- inferior mesenteric
venous drainage - portal veinous system
lymphatic - inferior mesenteric nodes
describe the vessels below the pectinate line
nerve - somatic, pudendal
arterial - internal iliac
venous - systemic venous system
lymph - superficial inguinal nodes
name the 2 blood vessels suppling the rectum and anal canal
- Inferior mesenteric artery
a. Supplies HINDGUT organs
i. Only extends as far as proximal half of anal canal so only above pectinate line - Internal iliac artery
a. Everything else
what arteries branch from the internal iliac artery
middle and inferior rectal artery
describe the venous drainage from rectum and anal canal
the inferior mesenteric artery drains the hindgut organs that are above the pectinate line and part of the portal venous system
the internal iliac vein drains below pectinate line and is part of the systemic venous system
where does the superior rectal vein drain into
inferior mesenteric vein
where do the middle and inferior rectal vein drain into
internal iliac vein
are rectal varices and haemorrhoids the same thing
no!
why do rectal varices form
portal hypertension
what are rectal varices
dilation of collateral veins between portal and systemic venous systems
what are haemorrhoids
prolapses of the rectal venous plexus - not related to portal hypertension
due to raised pressure e.g. cronic constipation, straining, pregnancy
where can you find the ischioanal fossae
either side of the anal canal
how do the two ischioanal communicate
posteriorly
what is the ischioanal fossae filled with
fat and loose connective tissue
what happens if you get an infection in the ischioanal fossae
ischioanal abscess
whats the fossae that can get abscesses that lies either side of anal canal
ischioanal fossae
whats the exam for viewing the interior of the colon
colonoscopy
whats the exam for viewing the interior of the sigmoid colon
Sigmoidoscopy
whats the exam for viewing the interior of the rectum
proctoscopy
