Reproductive System

1. David M. Phillips Reproductive System

2. 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

3. 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

5. California Dept. of Education • 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

6. 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

7. 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

9. 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

11. 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