Testes
The male reproductive system starts with the testes. The testes consist of two circular glands that reside in a skin sack called the scrotum. The testes produce two major products of the reproductive system called sperm and testosterone. The sperm are the male gamete, that combine with the female ovum during fertilization to produce a fetus. The testes also produce testosterone, which is an important hormone responsible for producing male sex characteristics.
Duct System
Once sperm has been produced, the testes discharge the sperm cells into a series of ducts. The first duct is the epididymis. This directs the sperm from the testis into the vas deferens. From the vas deferens, the sperm travels to the seminal vesicles.
Semen
The seminal vesicles are two glands located directly below the bladder. The seminal vesicles discharge a sticky and thick fluid that makes up the first part of semen. As the sperm continues to travel, the prostate secretes additional alkaline solution that makes up a large portion of the semen. This alkaline solution helps protect the sperm from the acidity in the man's urethra, and eventually the woman's, during intercourse.
Penis
Sperm exits the body through the penis. When a man becomes sexually excited, blood rushes to the large spaces in the penis called the corpora cavernosa. This causes the penis to become hard and rigid enough to enter the female reproductive tract through the vagina. Once the man has reached a certain point of sexual stimulation, ejaculation occurs. During ejaculation, the sperm-filled semen is ejected out of the urethra. If ejaculation occurs during sexual intercourse, the semen travels into the female reproductive tract where it can contribute to conception.
