David M. Phillips Reproductive System

Male Anatomy Sperm Production takes place in the testes which are located in the scrotum Located outside the body because sperm can develop only in an environment with a temperature 2-3 degrees Celsius lower than normal body temperature Muscles in the scrotum contract in response to cold temperatures and relax in warm weather

Formation of Sperm Within each testis is a fine network of highly coiled tubes. Sperm are produced by meiosis of the cells that line these tubes Recall that meiosis produces 4 haploid cells Each of these haploid cells develop into sperm over a period of about 74 days A sexually mature male can produce about 300 million mature sperm per day, about 400-500 million fit in a teaspoon Sperm usually live for about 24 hours inside the female reproductive tract

Sperm are highly adapted for reaching and entering the female egg The head portion contains the nucleus and is covered by a cap with enzymes that help penetrate an egg Mitochondria are found in the midpiece to provide energy The tail is a typical flagellum California Dept. of Education

The path of sperm Before the sperm mature they leave the testes through a series of coiled ducts that empty into a single tube called the epididymis where they mature From the epididymis the sperm enter the vas deferens where they are stored for as long as 2-3 months The sperm is transported out of the body via the urethra (same structure transports urine out of the body) A muscle prevents urine and sperm from mixing

When the sperm travels from the testes, they mix with fluids secreted from several different glands Seminal vesicles secrete a fluid rich in sugar fructose (energy) The prostate gland secretes a thin, alkaline fluid that helps the sperm move and survive Bulbourethral glands secrete an alkaline fluid to neutralize the acidic environment of the male urethra and female vagina The sperm and all these fluids together is called semen

Female Anatomy The main function of the female reproductive system are: To produce eggs Receive sperm Provide an environment for a fertilized egg to develop Egg production takes place in the two ovaries (in humans each is about the size of an almond) The eggs are transported from the ovary to the uterus via the oviduct The uterus is where a fetus develops during pregnancy (about the size and shape of a pear) and is composed of three layers: An outer layer of connective tissue A thick, muscular middle layer A thin, inner lining called the endometrium The lower end of the uterus tapers to a narrow opening into the vagina

Production of eggs With males, sperm production does not occur until puberty and continues the rest of their lives Egg production is different: even before a female is born, her body begins developing eggs Before birth, the cells in the ovaries divide until the first stage of meiosis and then go into a resting stage At birth, a female’s ovaries contain around 2 million of these potential eggs called primary oocytes Over time, many oocytes break down or degenerate At puberty, a female’s ovaries contain around 40,000 primary oocytes About once a month the process of meiosis starts up again and continues through meiosis. During which, one of the egg cells ruptures from the ovary and passes into the oviduct (ovulation) A total of around 400 eggs are ovulated during the reproductive life of a female