The male reproductive system is homologous in many ways to the female reproductive system, with different organs that carry out similar functions in both sexes. Unlike in females, however, most of the male reproductive organs are located outside the body as extremities. In this article, we’ll provide some details and images of the male reproductive system, including the major organs and structures, their locations and functions.
The male reproductive organs
The main male reproductive organs are the penis and the testes (testicles). The penis is the male sexual organ, and is made up of spongy tissue that fills with blood during sexual arousal, making it erect for sexual intercourse. The testes are small, olive-shaped organs which are responsible for making male gametes (sex cells), also known as sperm, as well as the hormone testosterone. Sperm produced in the testes will pass through several other structures and finally be released through the penis during ejaculation. Unlike females, who are born with all of their sex cells and do not make any new eggs, the testes will continue to produce sperm cells over the course of a male’s life.
For sperm to be able to stay healthy enough to fertilize an egg cell in sexual reproduction, they must be kept at a specific temperature that is slightly cooler than normal body temperature, which is why the testes are located on the outside of the body (as opposed to their female homolog, the ovaries, which are located inside the abdominal cavity). The testes are held in a fleshy sac called the scrotum which has special muscles which bring the testes closer to the body or father away depending on whether their temperature is too low or too high.
Other organs and structures in the male reproductive system include the urethra, vas deferens, prostate gland, Cowper’s glands, seminal vesicles, and the epididymis.
What is semen made of?
Semen is the fluid released from the urethra opening in the penis during ejaculation. It contains sperm cells, but the majority of semen is made up of water and sugars. Sperm produced in the testes first passes through the epididymis, where it matures and gains the ability to fertilize an egg cell, and then into the vas deferens. Attached to the vas deferens are seminal vesicles, which produce a sugary fluid high in fructose that mixes with the sperm cells and provides them the energy they need to swim. Fluid from these vesicles makes up most of the volume of semen that is released during ejaculation.
The sperm and seminal fluid flows into the urethra, which is the tube through which urine travels during urination in both men and women, and in males has the extra duty of letting semen exit through the penis when the man ejaculates. Before reaching the penis, the urethra passes through the center of the prostate gland, which contributes additional fluid to the semen, including nutrients for the sperm, while nearby glands known as Cowper’s glands add substances which will provide lubrication and protect the sperm from any acidity left behind by urine. Cowper’s gland secretions are the main component of pre-ejaculate fluid.
Semen is therefore a mixture of water, fructose, prostate fluid, mucoproteins from Cowper’s glands, sperm cells, nutrients and other trace substances.
Location of male reproductive organs
The penis and testes, both external organs, are connected by several structures inside the male body. The epididymis is located on top of and posterior to the testes inside the scrotum, and connects the testes to the vas deferens, which is a long tube that extends from the epididymis up into the abdominal cavity, above the urinary bladder, and then curves down between the urinary bladder and the rectum. Below the urinary bladder, the vas deferens terminates in the ejaculatory ducts, on top of which the seminal vesicles are located. Directly below the urinary bladder is the prostate gland; the urethra runs from the urinary bladder through the prostate gland and into the penis, and semen enters the urethra from the ejaculatory ducts. Finally, Cowper’s glands, which are about the size of a pea, are located beneath the prostate gland and between the root of the penis and the rectum.