Penis

Question 1

dorsal masses of penis

Answer 1

corpora cavernosa

Question 2

ventral mass of penis

Answer 2

corpus spongiosum

Question 3

tunica albuginea of penis

Answer 3

dense fibroelastic layer

binds cavernosa and spongiosum together and forms a capsule around each

Question 4

corpora cavernosa

Answer 4

contains most of the blood during erection

numerous wide, irregularly shaped vascular spaces lined with endothelium
- these spaces are surrounded by a thin layer of trabeculae consisting of collagen, elastic fibers, and SmM

each is supplied by a central artery, which gives off many helicine arteries –> which open into vascular spaces and dilate during erection to increase blood flow

Question 5

events that lead to erection

Answer 5

1. parasympathetic fibers release ACh
2. production of NO by SmM cells and endothelial cells
3. increased production of cGMP (potent vasodilator)
4. relaxation of SmM cells and dilation of helicine arteries
5. increased blood flow into corpora cavernosa
6. compress the venules against the non-distensible thick tunica albuginea (corporal veno-occlusive mechanism) - no blood drain
7. tunica albuginea also compresses the larger veins that drain from the corpora cavernosa so that venous outflow is blocked

Question 6

Viagra mechanism

Answer 6

inhibits cGMP-specific phosphodiesterase

responsible for degradation of cGMP, preserving SmM relaxation and prolonging the erection period

would NOT be effective if cGMP is impaired due to parasympathetic damage (complication of prostate cancer surgery)

Question 7

termination of erection

Answer 7

1. sympathetic stimulation
2. contraction of the trabecular SmM cells of the helicine arteries
3. decrease blood flow to corpora cavernosa
4. reduce the bp in the erectile tissue to normal venous pressure
5. allows the veins leading from the corpora cavernosa to open and drain the excess blood

Question 8

corpora spongiosum

Answer 8

spongy tissue surrounding the penile urethra

function in erection is to prevent compression of the urethra…so can still ejaculate

contain numerous irregularly shaped vascular spaces lined with endothelium

spaces are bounded by a thick layer of CT and SmM bundles –> “ subendothelial cushions”