1. The Reproductive System

2.  Reproduction is the formation of new individuals of the same species.  Sexual reproduction is the only method of reproduction in our species.  Sexual reproduction involves the fusion of specialised haploid sex cells.  The fusion of sperm and egg cell is called fertilisation.  Fertilisation results in the formation of a diploid zygote from which a new individual develops.

4. Sperm  Sperm is really just a haploid nucleus with a flagellum that propels it towards the egg cell.  The middle piece or neck contains mitochondria producing the ATP to supply energy for propulsion.  The head contains the nucleus with the genetic material.  It also has a large digestive enzyme sac, called the acrosome.  The digestive enzymes help the sperm to make their way to the surface of the egg cell.

7.  These are the features that distinguish the sexually mature individual from the immature.  They appear at puberty as a result of new higher levels of oestrogen in females and testosterone in males.  Primary Sexual Characteristics are the basic forms that distinguish between male and female i.e. the presence or absence of a penis!

8.  Hair growth on the face, underarm, chest and pubic region  Enlarged larynx producing a deeper voice  Wider shoulders  Greater skeletal musculature  Taller

9.  Hair growth in the pubic region and underarm  Enlarged breasts  Wide hips  Greater fat deposits under the skin  Taller

10.  The menstrual cycle is the repeating series of changes in the uterine lining of a fertile female if fertilisation and implantation does not happen.  This cycle ranges from 24 to 35 days, commonly 28 days.

13. Day 1 to day 5  Day 1 is the first day of menstruation.  The corpus luteum of the previous cycle has disintegrated.  The levels of oestrogen and progesterone declined greatly.  Low progesterone level leads to the menstruation.  Menstruation is the breakdown and discharge of the outer layer of the uterine lining.  Low oestrogen and progesterone levels permit the secretion of FSH (follicle stimulating hormone) by the pituitary gland.

14. Day 6 to day 13  FSH stimulated the formation and maturation of a Graafian follicle.  The maturing follicle secretes oestrogen.  Oestrogen inhibits FSH secretion preventing other follicles maturing.  Oestrogen also stimulates repair of the uterine lining.  Oestrogen brings about a surge of LH (luteinising hormone) just before ovulation.

15. Day 14  The surge of LH stimulates ovulation.  Ovulation is the release of the egg cell from the mature Graafian follicle at the ovary’s surface.  The egg cell is drawn into the Fallopian tube.

16. Day 15 to day 26  A corpus luteum (yellow body) develops from the ‘empty’ Graafian follicle.  The corpus luteum secretes progesterone and oestrogen.  These hormones stimulate the final maturation of the uterine lining.  High levels of theses hormones also inhibit FSH and LH secretion from the pituitary.  If implantation does not take place by day 26 the corpus luteum disintegrates.

17. Day 26 to day 28  The degeneration of the corpus luteum causes he levels of oestrogen and progesterone to decline rapidly.  The degenerated corpus luteum becomes a small scar in the ovary.

19.  Fertilisation is the fusion of the male gamete (sperm cell) and the female gamete (egg) to form a diploid zygote.  Fertilisation occurs in the Fallopian Tube usually.  Only one sperm cell can fertilise an egg and a chemical change occurs in the membrane of egg once fertilisation has taken place.  The most motile sperm will reach the egg first!

21.  The usual first sign that pregnancy has occurred is that menstruation does not happen.  Implantation is the embedding of the blastocyst (early developing embryo) into the uterine lining (endometrium).  Implantation occurs about six days after fertilisation.  The developing embryo releases a hormone into the mother’s blood.  This hormone maintains the corpus luteum.  The surviving corpus luteum continues to secrete progesterone and oestrogen.  As a result the endometrium (uterine lining) does not break down and the pregnancy continues.  Conception is fertilisation followed by successful implantation.

23.  Lactation is breastfeeding the baby with milk.  The placenta produced very high levels of oestrogen and progesterone.  After the birth of the baby these hormone levels fall rapidly.  This decline allows the pituitary to secrete prolactin hormone.  Prolactin stimulates the glands in the breasts to produce milk.  The suckling of a baby at the breast also stimulates the mother’s pituitary to release prolactin.  The regular presence of prolactin maintains milk production.  Suckling also stimulates the pituitary to secrete oxytocin.  Oxytocin causes the milk ducts to contract ejecting the milk from the breast.

24.  Family planning is a conscious action to control the number of and interval between children.  Contraception is the deliberate prevention of fertilisation or implantation. Natural Methods  Abstinence: no sexual intercourse. 0% failure rate.  Temporary abstinence: no sexual intercourse during the most fertile period of the menstrual cycle: 24% failure rate.  Withdrawal: penis is removed from the vagina before ejaculation: 25% failure rate.

25. Male Contraceptive Methods  Condom: a thin impermeable sheath covering the penis; semen cannot be deposited in the vagina: 10% failure rate.  Vasectomy: cutting, sealing or tying off the sperm ducts; sperm will not be in the semen: 0.4% failure.

27. Female Contraceptive Methods  Cervix Barriers: diaphragm or cap – prevents sperm entering the uterus: 15% failure rate.  Intrauterine Devices (IUD): these are plastic or metal loops or coils, prevents implantation: 5% failure rate.  Oral contraceptive pill: prevents ovulation as the follicles do not mature 6% failure rate.  Spermicides: these chemicals are placed in the vagina to kill sperm: 20% failure rate.  Tubal ligation: the Fallopian tubes are cut and sealed preventing sperm and egg cells meeting: 0.4% failure rate.