1. HUMAN DEVELOPMENT(in the uterus)(Biology Lesson Grade 8)Andreas Tjatur Witjaksana

2. (1). Every human being begins life as a single cell, formed when father's sperm fertilizes mother's egg.

3. (2).The process of fertilization involves a sperm fusing with an ovum.

4. (3).At fertilization, one sperm of the roughly 300 million in an average ejaculation fertilizes an egg to produce an offspring.

5. (4).At puberty, immature cells (spermatogonia) begin a maturation process (spermatogenesis). Spermatogenesis occurs in the seminiferous tubules of the testis.

6. (5).What is oogenesis? Oogenesis is the creation of an ovum (egg cell). Oogenesis occurs in the ovarian follicle of the ovary.

7. (6). Ovulation is the release of an egg cell from an ovary.

8. (7).How fertilization occurs? Fertilization is the first stage of human development. This process begins when a sperm unites with the mature ovum and it ends with the creation of the zygote . It normally occurs in the lateral third ( ampullary) part of the uterine tube, the widest part that lies close to the ovary, and usually fertilization process takes about 24 hours.

9. (8).After fertilization the single cell splits into two, then the two cells double to four, four to eight, eight to sixteen and so on. Because the cell cluster looks superficially like a berry it is called the morula.

10. (9).A morula is an embryo at an early stage of embryonic development. The morula is produced by embryonic cleavage, the rapid division of the zygote.

11. 10. The blastula is preceded by the morula and is followed by the gastrula in the developmental sequence.

12. (11). By the end of gastrulation, three embryonic germ layers – endoderm, mesoderm, and ectoderm - take their position in the embryo.

13. 12. These layers ultimately give rise to specific tissues and organs that make up the adult body plan.

14. 13. Later the embryo develops a placenta which serves as a connection between the newly developed embryonic membranes and the wall of the uterus.

15. (14).Gases and nutrients are exchanged at the placenta.

16. (15).The embryonic membranes are the chorion and amnion. They form a sac containing amniotic fluid in which the embryo , now called the fetus, floats.

17. (16).The umbilical cord, containing arteries and veins, connects the fetus to the plasenta.

18. (17).The fetus is completely developed after three months and during the remaining six month’s gestation it merely grows

19. (18).Childbirth (also called parturition) is the culmination of a human pregnancy or gestation period with the birth of one or more newborn infants from a woman's uterus.

20. (19).The placenta, the rest of umbilical cord and the amnion are all discharged as afterbirth.

21. (20).The baby is now an independent organism, inflating its lungs for the first time, followed soon afterwards by the working of its digestive systems, excretory system etc .