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Male reproductive system (human)
From Wikipedia, the free encyclopedia
The human male reproductive system is a series of organs located outside of the body and around the pelvic region of a male that contribute towards the reproductive process.
The male contributes to reproduction by producing spermatozoa. The spermatozoa then fertilize the egg in the female body and the fertilized egg (zygote) gradually develops into a fetus, which is later born as a child.
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The testes hang outside the abdominal cavity of the male within the scrotum. They begin their development in the abdominal cavity but descend into the scrotal sacs during the last 2 months of fetal development. This is required for the production of sperm because internal body temperatures are too high to produce viable sperm.
In the body of an average male, there are two testicles located in a sac called the scrotum. On top of these organs is the epididymis, the "housing area" for sperm that has been produced.
The penis has a long shaft and enlarged tip called the glans penis. The penis is the copulatory organ of the males. When the male is sexually aroused, the penis becomes erect and ready for intercourse. Erection is achieved because blood sinuses within the erectile tissue of the penis become filled with blood. The arteries of the penis are dilated while the veins are passively compressed so that blood flows into the erectile tissue under pressure.
A mature sperm, or spermatozoan, has 3 distinct parts: a head, a mid-piece, and a tail. The tail is made up of microtubules that form cilia and flagella, and the mid-piece contains energy-producing mitochondria. The head contains 23 chromosomes within a nucleus. The tip of the nucleus is covered by a cap called the acrosome, which is believed to contain enzymes needed to breach the egg for fertilization. A normal human male usually produces several hundred million sperm per day. Sperm are continually produced throughout a male's reproductive life, though production decreases with age.
During ejaculation, sperm leaves the penis in a fluid called seminal fluid. This fluid is produced by 3 types of glands, the seminal vesicles, the prostate gland, and Cowper's glands. Each component of a seminal fluid has a particular function. Sperm are more viable in a basic solution, so seminal fluid has a slightly basic pH. Seminal fluid also acts as an energy source for the sperm, and contains chemicals that cause the uterus to contract.