Ischioanal Fossae Flashcards
What is the ischioanal fossae and where is it located?
Wedge shaped spaces located between skin of anal region and pelvic diaphragm
-apex is superior where levator ani m. originate from obturator internus fascia
What is the ischioanal fossae filled with? what is the purpose?
adipose and C.T.
-permits expansion of anal canal during passage of feces
Where do the two fossae communicate?
via postanal space
What is the lateral boundary of the fossae?
ischium and obturator internus m. (fascia)
-pudendal canal located here
What is the medial boundary of the fossae?
anal canal surrounded by levator ani m. and external anal sphincter
What is the posterior boundary of the fossae?
sacrotuberous lig. and gluteus maximus m.
What is the anterior boundary of the fossae?
External urethral sphincter and deep transverse perineal m.
-anterior recess extends forward superior to perineal membrane
What is contained in the Pudendal canal?
internal pudendal a.v.
pudendal n.
obturator internus m.
-These enter canal at lesser sciatic notch in ischial spine
The branches of the internal pudendal a. form what?
Inferior rectal a.
Perineal a
Deep a. of penis (males) or Deep a. of clitoris (females)
Dorsal a. of penis (males) or Dorsal a. of clitoris (females)
What does the perineal a. supply? and what branches off?
supplies muscles of superficial pouch
- Males: Posterior scrotal a. and A. of bulb of penis
- Females: Posterior labial a. and A. of bulb of vestibule
What are the branches of the pudendal n.?
Inferior rectal n.
Perineal n.
Dorsal n. of penis/clitoris
Which nerves supplies external anal sphincter and perianal skin?
inferior rectal n.
What does the Perineal n. supply and what are its branches?
Supplies urogenital triangle
- Superficial perineal n. (forms posterior scrotal/labial n.)
- Deep perineal n.
What dos the deep perineal n. supply?
motor to muscles of deep/superficial perineal pouches
- sensory for inferior part of vagina and its vestibule
What is the primary sensory nerve of the glans?
dorsal n. of penis/clitoris
Anal canal
Terminal part of large intestine (approximately 3cm)
- Extends from pelvic diaphragm (Puborectalis m.) to anus
- Normally collapsed unless feces are passing through
Internal anal sphincter
Thickened circular smooth muscle around the superior 2/3 of anal canal
-Involuntarily controlled
How is the internal anal sphincter normally?
Normally tonically contracted (sympathetic) to prevent leakage of feces of flatus
-Reflexively relaxes in response to pressure of feces/gas in rectal ampulla
What nerve mediates relaxation of the internal anal sphincter?
pelvic splanchnic n.
External anal sphincter
Broad band of skeletal muscle surrounding inferior 2/3’s of anal canal
- Voluntarily controlled
- Attaches anteriorly to perineal body and posteriorly to coccyx (via anococcygeal lig.)
What does the external anal sphincter blend superiorly with?
Puborectalis m.
Which muscle bilaterally contracts to prevent defecation (or voluntarily relax)?
Puborectalis m.
What is the external anal sphincter innervated by?
inferior rectal n. (S4) from pudendal n.
What are the structure makes up the interior of the anal canal?
Anal columns
What are the anal columns?
Longitudinal ridges of mucosa in superior half of canal and contains terminal branches of Superior Rectal a.v.
What are the superior ends of the anal canals? Inferior?
superior –> anorectal junction
Inferior –> anal valves
What are the anal sinuses?
small recesses located just superior to anal valves
- produce mucous to facilitate passage of feces
What is the Pectinate line?
irregular line formed by anal valves
- Junction of hindgut (endoderm) with proctodeum (ectoderm)
What are the cells that make up the pectinate line above and below?
Superior: Simple columnar epithelium w/ goblet cells
Inferior: Stratified squamous non-keratinized epithelium
What are the arteries that supply the anal canal?
Superior rectal a. (from IMA) above pectinate line
Inferior rectal a. (Internal pudendal a.) below pectinate line
**Middle rectal a. anastomoses with both sup. and inf. rectal
What is the venous drainage of the anal canal?
- Superior to line: drains to hepatic portal system (via Superior rectal v.)
- Inferior to line: drains to IVC (via inferior rectal and internal pudendal v.v.)
What is the lymphatic drainage of anal canal?
above line = internal iliac nodes
below line = superficial inguinal nodes
What is the autonomic innervation above the pectinate line?
via hypogastric plexus
What is the sympathetic do? Parasympathetic?
Symp. = maintain tonus of internal anal sphincter
Para. = relax internal anal sphincter
-Responsive to distension/stretching but in sensitibe to touching/cutting
What is the somatic innervation below the pectinate line?
Inferior rectal n. (pudendal n.)
- Motor innervation to external anal sphincter
- Responsive to pain, touch and temperature
