2. Conception It is the consequence of several complex events that include the final maturation of the spermatozoa and the oocyte, transport of the gamete in the female genital tract, fusion of the male and female gametes.

3. The human body has two type of cells: 1- somatic cells ( diploid ) 46 have two copies of each chromosome one from the mother and the other from the father with the exception of sex chromosome x and y this cells are present in the different part of the body and divided by mitosis. 2- the mature germ cells ( sperm or egg ) have only one copy of chromosomes ( haploid ) 23, it under go special type of division called meiosis.

4. Development and maturation of the female gamete:  In utero the primordial follicles in the ovary enter the first meiotic division resulting in to primary oocyte but not completed until puberty ( ovulation ) and when completed results in the secondary oocyte and the 1st polar body.  Then the secondary oocyte enter the 2 nd meiotic division and not completed till fertilization to produce the female pro nucleus and second polar body  Diploid primary oocytes undergoes meiosis produces haploid mature ovum ( containing one polar body ).  Female ovum contain only 22+ X chromosomes.

6. The development and maturation of the male gametes(spermatogenesis)  In the seminiferous tubules the spermatogonia divide mitotically at the onset of puberty to produce primary spermatocyte.  These undergo a 1 st meiotic division to produce the secondary spermatocytes.  The diploid secondary spermatocytes further undergo the 2nd meiotic division to produce haploid spermatid which are subjected to some morphological change to produce mature sperm a process called( spermiogenesis ).  Sperm acquired active motility while passing through male genital tract  The sperm contain 22+ X or Y chromosomes  Spermatogenesis in human usually completed in a period of 3 months.

7. Fertilization  Is the fusion of male and female gametes to form the zygot and reestablish the diploidy it will be either 46 XX (female) or 46 XY (male)  The end product of the oogenesis and oocyte maturation is the Graafian follicle the oocyte surrounded by zona pellucida, granulosa cells ( the most intimate called cumulus oophorus ) theca cells ( Theca interna and Theca externa with eccentric fluid collection ( antrum ) at ovulation.  The ovulated egg is picked up by the fimbria of the fallopian tube and then swept by ciliary action towards the, ampulla where fertilization occurs.  Oocyte remain viable for only 24hrs within the female genital tract if fertilization not occur it will die out.

8.  Sperm passing through female genital tract and will move towards the ampulla, where fertilization of the mature ovulated oocyte usually occurs.  sperm remain for seven days in the female genital tract.  the seminal fluid is alkaline.  In the female genital tract sperm undergo capacitation process in which the inner membrane beneath the acrosome cap becomes primed for fusion with the inner membrane of the ovum.  The acrosomal reaction exposes the inner membrane of the sperm. This portion will fuse with the membrane of the ovum.

9.  Following penetration of the oocyte the male pronucleus formed.  The egg must complete its 2nd meiotic division to form the haploid female pronucleus and 2nd polar body is extruded.  fertilization is completed by the fusion of male and female pronuclei to form zygote after about 20 hrs.  As soon as zygote is form, cleavage occur in form of a rapid successive mitotic divisions that produce the morula stage and then fluid filled cavity is formed and an inner cell mass identified attached eccentrically to the outer layer of flattened cells the embryo at this stage is called the blastocyst(stage of implantation ).

11. Implantation:  The zygot remain in the fallopian tube for 3-4 days and enter the uterine cavity in the (morula) stage. It float freely for up to 72 hours in the uterine cavity.  By the sixth day following fertilization the blastocyst within the uterus become adherent to the decidual epithelium results in implantation.  The Successful implantation requires a receptive endometrium that has been appropriately primed with oestrogen and progesterone ( decidulized ).  The early steps of implantation required many cell to cell inter action to allow the invading embryo to access to the decideua for implantation this mediated by many proteolytic and cytokines mediaters.

12.  The cells of blastocyst are differentiated into outer layer mass called( trophoblasts ) give rise to the placenta and inner cell mass ( embryoblasts ) give rise to the embryo.  The trophoblast differentiated into cytotrophoblast and syncytiotrophpblast which are the sites of the production and secretion of HCG ( a poly peptide hormones that prevent the degeneration of the corpus luteum resulting in to pregnancy support and used as a biochemical marker in the urine and blood to confirm the presence of pregnancy ).

14. Embryology: Following successful fertilization, the differentiation of cells into specialized tissues to form interrelated organ system, is known as the embryonic period. It starts with the generation of the embryonic disc during the 2nd week post fertilization ( 4 th weeks after LMP ) and ends at the last day of 8th weeks (10th weeks after LMP). During this period all organ systems are formed then gradually become mature and functioning later on. This period is very critical, exposure to drug, toxin, infection or radiation ( teratogens )during the embryonic period lead to damage and malformation of the different body organs.

15. Amniotic fluid  It is a fluid that filled the amniotic cavity, usually turbid from admixture of solid particles derived from fetal skin and amniotic epithelium.  It may stained green or brown in colour if contain meconium and bloody if contain blood  It is alkaline (pH 7).  By 12 weeks gestation, the amniotic comes into contact with the inner surface of the chorion and the two membranes become adherent.  Neither the amnion nor the chorion contains vessels or nerves

16.  The amniotic fluid produced both from maternal and fetal sites and the mechanism change as the pregnancy progress. Early in pregnancy, the amniotic fluid is initially secreted by the amnion. By the 10th week it is mainly a transudate of the fetal serum via the skin and umbilical cord. From 16 weeks gestation, the fetal skin becomes impermeable to water and from this time on word the fetal kidney play an increasing role in the production of amniotic fluid and small lung fluid.  At term about 500 ml l day are secreted and absorbed.

17. Disposal of the amniotic fluid: Partly by the absorption through the amnion in to the maternal plasma and partly by fetal swallowing and absorption in to the intestine to enter fetal circulation.

18. Amniotic fluid volume  Amniotic fluid volume increases progressively ( 10 weeks:30 ml ; 30 weeks:600 mL ; 38 weeks: 1000 mL ), but from term there is a rapid fall in volume ( 40 weeks:800 mL; 42 weeks: 350 mL ). The reason for the late reduction has not been explained.

19. The function of the amniotic fluid is to: 1-Protect the fetus from mechanical injury.2-permit fetal movement 3- prevent limb contracture 4- prevent adhesion between fetus and amnion 5- permit fetal lung development 6-mentain fetal body temprture and prevent heat loss 7- the for water bag act as a mechanical dilator to the cervix when uterine contraction starts 8- during labour when the membrane ruptured the amniotic fluid clean the lower birth canal as the fluid has a bactercidal activity 9- it may have nutritional benefit as it contains protein and salt 10-the amnion secret a lot of cytokines and growth factors 11- amniotic fluid can be aspirated abdominally during pregnancy to investigate many conditions a procedure called amniocentesis