Key POINTS Sexual Education Reproduction of living organisms: Reproduction in humans Textbook reference: PP 257-261 Objective: All mammals begin their life as a tiny fertilized egg. In this chapter, we will look at sexual anatomy, development of a foetus, contraceptive methods and sexual transmitted infections (STI’s).
1. The reproductive system: a system that produces and combines male and female gametes in order to reproduce. Reproduction occurs by internal organization. Gametes: males and female sexual cells: Sperm in males and egg in females.
Hormones: chemical messengers that travel in the body though the bloodstream and tell the testicles (in boys) and ovaries (in girls) when to begin producing gametes (sperm and egg). • Puberty: a period that begins when hormones cause changes in the bodies of boys and girls. These changes are designed to prepare them for reproduction.
Pituitary gland: a gland located at the base of the brain. In humans, it is about the size of a pea. It releases sex hormones. • In males, the sex hormone is testosterone (Released by the testicles). • In females, the sex hormones are progesterone and estrogen. (Released by the ovaries). • Testosterone triggers the testicles to produce spermatozoa (Sperm). • Progesterone and estrogen trigger the ovaries to produce ova (Eggs-plural). There is a period in each month where a menstrual cycle occurs. In this cycle, an ovum (Egg-singular) develops and is released by the ovaries. • Puberty also leads to other physical changes.
d) The menstrual cycle: a cycle that lasts about 28 days. It causes changes to the female reproductive organs: • 1) The lining of the uterusthickens to help the uterus implant and begin development. • 2) A woman’s body temperature increases during ovulation.
3) If an ovum is not fertilized by a sperm after a few days, it is expelled from the body along with the cells that lined the uterus, this is called menstruation..
2. Pregnancy: A male gamete meets and fertilizes a female gamete. a) Steps of fertilization: 1. Fertilization occurs when spermatozoa are deposited in the vagina during intercourse. 2. The sperm then swims in the fallopian tubes until they reach an ovum. 3. Of the several million spermatozoa released only a few thousand will reach the ovum. 4. Only one will succeed in fertilizing the ovum.
When a sperm fertilizes an egg, it now becomes a zygote. The zygote then moves from the fallopian tube into the uterus. As it travels down to the uterus, it undergoes cell division. By the time, it reaches the uterus, it is now a clump of 16 cells, and hence it is divided three times. Just before depositing in the uterus, the zygote now looks like a fluid-filled sac. It has a group of cells called embryoblast. External cells become the placenta. 10.The embryoblast become the embryo.
4. Family planning: Factors that affect animal production of gametes are seasons (Climatic change), quantity and quality of food available. As for humans, females produce an ovum every month and males produce spermatozoa every day.
Contraception: Contraception causes temporary or permanent sterility in men and women. Certain methods of contraception prevent fertilization, or the union of a spermatozoon with an ovum. Others prevent the zygote from implanting in the uterus. The following (Next slide) is a table that describes different contraceptive methods and devices: