Question

Describe a) the blood supply and intervation of the penis and b) explain how it determines erection and ejaculation.

Answer 1

Arleries of lhe Pen"s
1.The intemal pudendal artery gives off three branches
which supply the pen"s.
a. The deep artery of the pe"is runs in the corpus
cavernosum. It breaks up into arteries that follow
a spiral course and are, therefore, called helicine
arteries.
b. The dorsal artery of the pen"s runs on the dorsum,
deep to the deep fascia, and supplies the glans
pen"s and the distal part of the corpus spongiosum,
the prepuce and the frenulum.
c. The artery of the bulb of the pen"s supplies the bulb
and the proximal half of the corpus spongiosum.
2 The femoral artery gives off the superficial external
pudendal artery which supplies the skin and fasciae
of the pen"s.
Veins of the pen"s.
The dorsal veins, superficial and deep, are unpaired.
Superficial dorsal vein drains the prepuce and pen"le
skin. It runs back in subcutaneous tissue and inclines
to right or left, before it opens into one of the external
pudendal veins.
Deep dorsal vein lies deep to Buck's fascia. It receives
blood from the glans pen"s and corpora cavernosa pen"s, and courses back in midline between paired
dorsal arteries.
Near the root of the pen"s, it passes deep to the
suspensory ligament and through a gap between the
arcuate pubic ligament and anterior margin of perineal
membrane, it divides into right and leftbranches which
connect below the symphysis pubis with the internal
pudendal veins and ultimately enters the prostatic
plexus.

Erection of the pen"s is a purely vascular phenomenon.
The turgidity of the pen"s   during its erection is
contributed to by the following factors.
1 Dilatation of the helicine arteries pours an increased
amount of arterial blood into the cavernous spaces of
the corpora cavemosa. Blood is also poured in small
amount into the corpus spongiosum and into the
glans by their arteries. As the spaces within the
erectile tissue fill :up, the pen"s enlarges.
2 This enlargement presses on the veins preventing
outflow of blood through them. Contraction of the
ischiocavernosus muscles probably has the same
effect.
3 Expansion of the corpora cavernosa, and to a lesser
extent of the corpus spongiosum, stretches the deep
fascia. This restricts enlargement of the pen"s. Further
flow of blood increases the pressure within the
erectile tissue and leads to rigidity of the pen"s.
4 Erection is controlled by parasympathetic nerves
(nervi erigentes, 52, 53, S4)