Male Reproductive System - Semen

Semen: a mixture of sperm and seminal fluid.
The volume of an average ejaculate is 2.5-5 ml. with 50–150 million sperm per ml.
The pH is 7.2–7.7
Penis: containing the urethra it is a passageway for semen and urine.
Composed of 3 cylindrical masses: 2 corpora cavernosa, 1 corpus spongiosum (all erectile tissues).
Glans: Head of penis covered by the prepuce (foreskin).

The penis is supported by the fundiform and suspensory ligaments.
An erection is brought about by parasympathetic innervation leading to vasodilation of arterioles in erectile tissue.
Large amounts of blood enter the tissue into dilated blood sinuses.
Ejaculation is the powerful release of semen due to sympathetic stimulation. The bulbospongiosus, ischiocavernosus and superficial transverse perineal muscles contract to force the semen out.