Ischioanal Fossae

Question 1

What is the ischioanal fossae and where is it located?

Answer 1

Wedge shaped spaces located between skin of anal region and pelvic diaphragm
-apex is superior where levator ani m. originate from obturator internus fascia

Question 2

What is the ischioanal fossae filled with? what is the purpose?

Answer 2

adipose and C.T.

-permits expansion of anal canal during passage of feces

Question 3

Where do the two fossae communicate?

Answer 3

via postanal space

Question 4

What is the lateral boundary of the fossae?

Answer 4

ischium and obturator internus m. (fascia)

-pudendal canal located here

Question 5

What is the medial boundary of the fossae?

Answer 5

anal canal surrounded by levator ani m. and external anal sphincter

Question 6

What is the posterior boundary of the fossae?

Answer 6

sacrotuberous lig. and gluteus maximus m.

Question 7

What is the anterior boundary of the fossae?

Answer 7

External urethral sphincter and deep transverse perineal m.

-anterior recess extends forward superior to perineal membrane

Question 8

What is contained in the Pudendal canal?

Answer 8

internal pudendal a.v.
pudendal n.
obturator internus m.
-These enter canal at lesser sciatic notch in ischial spine

Question 9

The branches of the internal pudendal a. form what?

Answer 9

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)

Question 10

What does the perineal a. supply? and what branches off?

Answer 10

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

Question 11

What are the branches of the pudendal n.?

Answer 11

Inferior rectal n.
Perineal n.
Dorsal n. of penis/clitoris

Question 12

Which nerves supplies external anal sphincter and perianal skin?

Answer 12

inferior rectal n.

Question 13

What does the Perineal n. supply and what are its branches?

Answer 13

Supplies urogenital triangle

• Superficial perineal n. (forms posterior scrotal/labial n.)
• Deep perineal n.

Question 14

What dos the deep perineal n. supply?

Answer 14

motor to muscles of deep/superficial perineal pouches

- sensory for inferior part of vagina and its vestibule

Question 15

What is the primary sensory nerve of the glans?

Answer 15

dorsal n. of penis/clitoris

Question 16

Anal canal

Answer 16

Terminal part of large intestine (approximately 3cm)

• Extends from pelvic diaphragm (Puborectalis m.) to anus
• Normally collapsed unless feces are passing through

Question 17

Internal anal sphincter

Answer 17

Thickened circular smooth muscle around the superior 2/3 of anal canal
-Involuntarily controlled

Question 18

How is the internal anal sphincter normally?

Answer 18

Normally tonically contracted (sympathetic) to prevent leakage of feces of flatus
-Reflexively relaxes in response to pressure of feces/gas in rectal ampulla

Question 19

What nerve mediates relaxation of the internal anal sphincter?

Answer 19

pelvic splanchnic n.

Question 20

External anal sphincter

Answer 20

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.)

Question 21

What does the external anal sphincter blend superiorly with?

Answer 21

Puborectalis m.

Question 22

Which muscle bilaterally contracts to prevent defecation (or voluntarily relax)?

Answer 22

Puborectalis m.

Question 23

What is the external anal sphincter innervated by?

Answer 23

inferior rectal n. (S4) from pudendal n.

Question 24

What are the structure makes up the interior of the anal canal?

Answer 24

Anal columns

Question 25

What are the anal columns?

Answer 25

Longitudinal ridges of mucosa in superior half of canal and contains terminal branches of Superior Rectal a.v.

Question 26

What are the superior ends of the anal canals? Inferior?

Answer 26

superior –> anorectal junction

Inferior –> anal valves

Question 27

What are the anal sinuses?

Answer 27

small recesses located just superior to anal valves

- produce mucous to facilitate passage of feces

Question 28

What is the Pectinate line?

Answer 28

irregular line formed by anal valves

- Junction of hindgut (endoderm) with proctodeum (ectoderm)

Question 29

What are the cells that make up the pectinate line above and below?

Answer 29

Superior: Simple columnar epithelium w/ goblet cells
Inferior: Stratified squamous non-keratinized epithelium

Question 30

What are the arteries that supply the anal canal?

Answer 30

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

Question 31

What is the venous drainage of the anal canal?

Answer 31

• 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.)

Question 32

What is the lymphatic drainage of anal canal?

Answer 32

above line = internal iliac nodes

below line = superficial inguinal nodes

Question 33

What is the autonomic innervation above the pectinate line?

Answer 33

via hypogastric plexus

Question 34

What is the sympathetic do? Parasympathetic?

Answer 34

Symp. = maintain tonus of internal anal sphincter
Para. = relax internal anal sphincter
-Responsive to distension/stretching but in sensitibe to touching/cutting

Question 35

What is the somatic innervation below the pectinate line?

Answer 35

Inferior rectal n. (pudendal n.)

• Motor innervation to external anal sphincter
• Responsive to pain, touch and temperature