|Male external genitalia||Image|
MALE EXTERNAL GENITALIA
These refer to the reproductive organs that are not placed internally.
In the female they are the vulva and vestibule. In the male they are penis with its contained urethra and the scrotum.
Penis: This is the copulatory organ of the male. It has three main internal structures which are two corpora cavernosa and one corpus spongiosum. The corpora cavernosa are continuous with the crura of penis or clitoris which is its homologue. The corpus spongiosum on the other hand, is continuous with the bulb of penis. The (spongy) urethra transverses the penis, while the does arteries of the penis transverse the corpora cavernosa and their adjoining crura of penis. The penis is drained by superficial and deep dorsal veins of penis while its main arterial supply is from the deep artery of penis which is a branch of the internal pudendal artery.
The penis covered by penile fascia and is attached to the suspensory ligament of the penis which is continuous with the Scarpa’s fascia.
Mechanism of erection in the penis.
This mechanism is dependent on the ability of the spongy tissue (corpora cavernosa) to become engorged with blood, usually arterial blood. This is caused by the contraction of the ischiocavernosus muscle which assists the closure of the drainage pathway of the arteries. Also, it is believed there is a concomitant venoconstriction which helps to keep blood within the spongy tissues of the penis. This mechanism is released after the arousal has passed so that the organ becomes flaccid again. A bone does not exist in penis of man as it does in many animals. This bone is called os penis.
The penis is also responsible for the second stage of ejaculation which involves the emptying of the urethra by the assistance of the bulbospongiosus muscle.
The corpus spongiosum is attached to the glans penis or the head of the penis. The glans is the most sensitive part of the penis, and the penis is the most sensitive part of the whole of the male anatomy. In fact it is the only part that is sexually arousable by touch. The most arousable part of the glans is its crown. The glans is covered by a prepuce or foreskin. This skin is removed at circumcision in order to permanently expose the glans penis.
Scrotum is that sac that houses the testicles (testes), It has a skin that is wrinkled like the skin of an old man. This is a temperature regulating mechanism. Underneath is the layer of dartos muscle which also helps temperature regulation. The dartos muscle is continuous with Scarpa’s fascia.
Then the 3 layers of the spermatic cord lines the covering of the scrotum as follows.
Arteries of the male external genitalia
Veins of male external genitalia
Nerve supply of male external genitalia
From L1 nerve to anterior 1/3
From S3 nerve to posterior 2/3 of scrotum (2)
Exposure of male perineum
Penis and scrotum
Uncircumcised penis with retracted prepuce
1 glans penis 2 corona glandis 3 neck 4 shaft 5 root 6 hairline on mons pubis 7 scrotum
Prepuce covering glans in uncircumcised penis
Scrotum showing contained testes. Central perineal tendon and anus are below
Anal perineum and scrotum
1 dorsal artery of penis 2 deep artery of penis 3 perineal artery 4 Internal pudendal artery 5 Inferior rectal artery
1 pudendal nerve 2 inferior rectal nerve 3 perineal nerve 4 dorsal nerve of penis