the anal triangle Flashcards
what divides the UG and anal triangle?
imaginary line between ischial tuberosities
which triangle is found anteriorly?
UG triangle
which triangle is found posteriorly?
anal triangle
what does the anorectal junction denot?
separation between the rectum and the canal
what do the rectal folds lead to?
rectal ampulla
what does the bottom portion of the anus transition into?
transitions from being a mucosal membrane to a region where there is perianal skin
what is the function of the perianal skin?
Protective mechanism for the anal surface
what nerve innervated levator ani muscle?
pudendal N
what controls the internal anal sphincter?
automatically controlled by splanchnic nerves
what type of control is exerted on external anal sphincter?
somatic
what does the perineal body lead to?
leads posterior to anal body
what is created by the perineal membrane
deep and superficial perineal pouches
what is the ischiorectal fossa?
Pyramidal space located in the anal triangle
what is contained within the ischiorectal fossa?
2 large fat pads
Pudendal N
Internal pudendal A & V
what borders the ischiorectal fossa?
medial: levator ani
lateral: obturator internus
anterior: recess of ischiorectal fossa
base: skin and fascia
are the ischiorectal fossa and deep perineal pouch distinct?
no, they are continuous anteriorly
where does the superior rectal A come from
comes from ima
where does middle rectal A come from
internal iliac anterior division
how does the middle rectal A travel
Enters through the true pelvis and stays deep to levator ani muscle
where does the inferior rectal A come from
from internal pudendal A
where does the internal pudendal A come from
internal iliac A (anterior)
how does the internal pudendal A travel?
Travels by exiting the greater sciatic foramen and travels posterior to the ischial spine to come back through the lesser sciatic foramen and superficial/external to levator ani muscle
where can the inferior rectal A be found
Found within the perineum anal triangle
where does the superior rectal V drain into? what system?
drains into the inferior mesenteric V
Connects with portal venous system
where does the middle rectal V drain into? what system?
Drains into internal iliac V
Connect with systemic/Caval venous system
where does the inferior rectal V drain into? what system?
Drains into the internal pudendal V
Connect with systemic/Caval venous system
what is a hemorrhoid?
swelling of the internal/external anus where veins tend to stretch causing for improper blood flow and accumulation of blood in stretched veins
how is the superior portion of the pectinate line innervated?
autonomic innervation
what provides sympathetic innervation to the superior portion of pectinate line?
pelvic and sacrosplanchinic N
what types of haemorrhoids are found above the pectinate line?
internal
not painfull due to associated with autonomic NS
how is the inferior portion of the pectinate line innervated?
somatic innervation
what provides somatic innervation to the superior portion of pectinate line?
Pudendal N (S2-S4) to external anal sphincter and puborectalis
what types of haemorrhoids are found above the pectinate line?
external/perianal skin
more painful and visible
what is the importance of the pectinate line?
• Divides regions of the rectum and anus supplied by somatic or autonomic innervation, portal or caval drainage, arterial supply from IMA or internal iliac branches and differences between lymphatic drainage
what does the SHP split into?
hypogastric N on either side and merges in the inferior hypogastric plexus
what provides parasympathetic innervation to rectum and anal canal?
Pelvic splanchnic N via inferior hypogastric plexus
what provides sympathetic innervation to rectum and anal canal?
lumbar and sacral splanchnic N
what type of innervation Stimulates contraction of the rectum/anus and relaxes the internal anal sphincter
parasympathetic innervation
where does sympathetic innervation come from?
IHP
what type of innervation Inhibits contraction of the rectum and anus and contracts the internal anal sphincter to prevent defecation (tonic contraction of the sphincter to prevent anal leakage (incontinence)
Sympathetic
what is controlled by somatic innervation
Allows control of the urge to defecate and need to release these muscles to allow time to relax for defectation to occur
what nerve provides somatic innervation?
Pudendal N to external anal sphincter and puborectalis
how does defecation occur
- Mass movement in the large intestine triggers defecation reflex which stimulates distension in the rectum
- Contraction of sigmoid colon and rectum
- Defecation: relaxation of puborectalis and external anal sphincter
where does the lumbar splanchic N begin and where does it travel to?
N begin in the SHP & make their way down into IHP
where does the sacral splanchic N begin and where does it travel to?
makes their way down directly to the IHP
what happens during contraction of the sigmoid colon and rectum
Relaxation of internal anal sphincter (autonomic)
Contraction of external anal sphincter and pelvic floor (puborectalis)
what controls the urge to defecate?
pudendal N
is reverse peristalsis of fecal matter possible?
yes
