Male Perineum

Question 1

Location, shape and borders of perineum

Answer 1

Below pelvic floor
Diamond shaped
Inferior pubic symphysis, ischial tuberosity, coccyx

Question 2

What are the two halves of the diamond shaped perineum?

Answer 2

Urogenital triangle - anterior

Anal triangle - posterior

Question 3

What perforates the perineal membrane?

Answer 3

Urethra

Question 4

What is located in the anal triangle?

Answer 4

Anal canal and fat from the ischioanal fossa

Question 5

Where is the superficial perineum?

Answer 5

Inferior or superficial to the perineal membrane

Question 6

What are the erectile tissues of the penis?

Answer 6

Corpus cavernosum and corpus spongiosum

Question 7

Describe the positioning of the corpus cavernosa?

Answer 7

Have two crura (crus of penis x2 ) which attach to perineal membrane

Corpus cavernosa attached medially, and overly the corpus spongiosum

Question 8

Describe attachment of corpus spongiosum

Answer 8

Bulb of penis attached to perineal membrane and ischial rami at proximal end of the corpus spongiosum

Question 9

What structures form the root of the penis? Where do they attach?

Answer 9

Bulb and crura of the penis

Attach to ischial rami and perineal membrane

Question 10

What structure is at distal end of corpus spongiosum?

Answer 10

Glans penis

Question 11

What muscle covers the bulb of the penis and the corpus spongiosum?
Function and innervation of this muscle

Answer 11

Bulbospongiosus - contracts to empty contents of spongy urethra and maintains erection
Innervated by somatic fibres from pudendal nerve S2-S4

Question 12

How is erection maintained?

Answer 12

Constriction of bulbospongiosus in proximal penis increases pressure in bulb of penis, restricted blood flow through deep dorsal vein of penis

Question 13

Which muscle covers the corpora cavernosa and crura of penis?
Function and innervation

Answer 13

Ischiocavernosus - force blood from crura into distal parts of corpus cavernosa, increasing distension/swelling of penis in erection and restricting blood flow out of veins in corpus cavernosa (maintain erection)

Innervated by somatic fibres in pudendal nerve S2-S4

Question 14

Attachment, function and innervation of superficial transverse perineal muscle

Answer 14

Ischial rami and perineal body

Maintain position of perineal body (important muscle attachment site)

Question 15

Histology of erectile corpora of penis

Answer 15

Endothelial like blood spaces separated by trabeculae of fibrous tissue and smooth muscle

Question 16

What arteries supply the erectile tissue and surrounding structures? Location, supply region and origin?

Answer 16

Deep artery = inside corpora cavernosa, to erectile tissue
Dorsal artery = superior to the corpora cavernosa, but within the surrounding deep fascia, to superficial structures

Supplied by internal pudendal artery

Question 17

What veins drain the penis?

Answer 17

Superficial (outside of deep fascia) and deep (within boundary of deep fascia) dorsal veins

Question 18

What is the course of the internal pudendal artery?

Answer 18

Internal iliac —> Lesser sciatic foramen —> pudendal canal/ischioanal fossa

Question 19

What artery supply the scrotum, and what origin?

Answer 19

Anterior scrotal artery from external pudendal artery from femoral artery
Posterior scrotal artery from perineal artery from internal pudendal artery from internal iliac artery

Question 20

What is the situation in the penis when in the relaxed state?

Answer 20

Blood flow to arteries in corpus cavernosa minimal due to closure of the sinuses

Question 21

What nerves stimulate erection? Where do they originate?

Answer 21

Cavernous nerves of the prostatic plexus, from pelvic splanchnic nerves (S2-4), have parasympathetic fibres which relax the smooth muscle cells in the helecine arteries of the corpora reducing blood flow

Increased pressure reduces venous return through dorsal vein and causes penile distension

Question 22

Which nerves and muscles mediate somatic control to maintain erection?

Answer 22

Bulbospongiosus and ischiocavernosus, innervated by pudendal nerve S2-4, contract to restrict venous return further

Question 23

Which nerve stimulates emission of semen from the epididymal ducts and how?

Answer 23

Sympathetic nerves of the inferior hypogastric plexus, formed by:

–sympathetic fibres from hypogastric nerve

–sacral splanchnic nerves from sympathetic chain

Peristaltic contraction of SMCs surrounding ducts of epididymis, vas deferens, seminal vesicles and prostate

Question 24

What nerve stimulates what muscle to prevent retrograde ejaculation into the bladder?

Answer 24

sympathetic nerves from L1-2 stimulating contraction of internal urethral sphincter

Question 25

What nerves stimulate ejaculation? How do they do this

Answer 25

SOMATIC pudendal nerves S2-4

Stimulate contraction of bulbospongiosum moving semen along urethra

Question 26

The scrotum is part of the superficial perineal pouch? True or false

Answer 26

True