Male reproductive system
| Structure | Function |
|---|---|
| Testes | Produce sperm (male gametes) and testosterone |
| Scrotum | Holds the testes outside the body at a slightly lower temperature for optimal sperm production |
| Sperm duct (vas deferens) | Carries sperm from the testis to the urethra |
| Prostate gland and seminal vesicles | Add fluid to sperm to form semen, providing nutrients and a transport medium |
| Urethra | Carries semen (and urine at other times) out through the penis |
| Penis | Deposits semen in the female reproductive tract during sexual intercourse |
Female reproductive system
| Structure | Function |
|---|---|
| Ovaries | Produce eggs (ova, the female gametes) and oestrogen and progesterone |
| Oviducts (fallopian tubes) | Carry the egg from the ovary toward the uterus; fertilisation usually occurs here |
| Uterus (womb) | Where the embryo implants and develops; has a thick muscular wall and a blood-rich lining |
| Cervix | Ring of muscle at the base of the uterus; dilates during childbirth |
| Vagina | Receives the penis during sexual intercourse; serves as the birth canal |
Gametes and their adaptations
The sperm cell is adapted for reaching and fertilising the egg: it has a streamlined head with an acrosome containing enzymes to penetrate the egg, a large number of mitochondria in the middle section to release energy for swimming, and a tail (flagellum) for locomotion. Millions are produced because most do not reach the egg.
The egg cell (ovum) is much larger than the sperm. It has a large store of cytoplasm containing nutrients for the early development of the embryo after fertilisation. It has a cell membrane that changes after the first sperm enters to prevent further sperm from fusing (the cortical reaction at Supplement level).
Hormones in puberty
At puberty, the pituitary gland stimulates the testes to produce testosterone and the ovaries to produce oestrogen. Testosterone causes the development of male secondary sexual characteristics: deepening of the voice, growth of facial and body hair, muscle development and sperm production. Oestrogen causes female secondary sexual characteristics: breast development, widening of hips, pubic hair growth and the start of the menstrual cycle.
These hormones do not need to be memorised in great detail at Core level, but Supplement students must link them to the menstrual cycle.