Semen is a substance produced by the male reproductive organs. It is composed of spermatozoa in a semi-viscous fluid. Structures within the male reproductive tract that are involved in the production of semen include:
- Testes and epididymis
- Seminal vesicles
- Bulbourethral gland
Semen is produced as a combination of secretions from the different regions of the male reproductive tract. Each fraction differs in chemical composition and function. The combination of these fractions during ejaculation results in the optimal environment for transporting sperm to the endocervical mucus in the female.
- Spermatozoa are produced in the testes. They mature in the epididymis. The testes also produce testosterone and inhibin.
- Fluid from the seminal vesicles accounts for approximately 70% of semen volume. The seminal vesicles are the source of fructose in semen. Fructose is used by the spermatozoa as an energy source.
- The prostate gland supplies about 20% of the volume of semen. Its fluids include acid phosphatase and proteolytic enzymes that lead to coagulation and subsequent liquefaction of semen. The prostate also contains most of the IgA found in semen.
- The bulbourethral gland produces mucoproteins that make up about 5% of the volume of semen.