The document summarizes the process of conception from the release of an ovum and sperm through implantation and development of embryonic and fetal structures. It describes how a zygote forms when an ovum and sperm fuse, then divides and develops into a morula and blastocyst as it moves through the fallopian tubes and uterus. The blastocyst implants in the endometrium around 8-10 days after fertilization. The placenta and other structures such as the amniotic sac, amniotic fluid, chorionic villi, umbilical cord and decidua develop to support fetal growth and development.

1. THE PROCESS OF CONCEPTION

2. OVAReleased from the Graafian FollicleWill be surrounded by a ring of mucopolysaccharide fluid (Zonapellucida) and a circle of cells (Corona radiata)Zonapellucida and Corona Radiata protects the ova by serving as a buffer against injuryMoves from the ovary to the fallopian tube through the cilia and peristaltic movement of fallopian tube

3. SPERMPer ejaculation, 2.5ml semen containing 50-200M spermatozoa is released (ave 400M sperm/ejaculation)Moves through the cervix, uterus, fallopian tube because of their flagella and uterine contractionsUndergoes CAPACITATION (changes in the plasma membrane of the sperm head to reveal sperm binding receptor sites) before penetrating into the corona radiata

4. Sperm clusters around coronal cellsWill release HYALURONIDASE (proteolytic enzyme) to dissolve the corona radiataSperm penetrates the cell; cell membrane of ova changes composition to become impenetrable to other sperm

5. Sperm and ova fuse carrying 23 pairs of chromosomes eachIf sperm carries X sex chromosome paired with the ovum X chromosome = female zygoteIf sperm carries Y sex chromosome paired with the ovum X chromosome = male zygote

6. IMPLANTATIONZygote move from fallopian tube to uterusIt will undergo series of mitotic divisions resulting to a cleavage formation, 1 in every 22 hour, with the cleavage division happening 24 hours after fertilizationOnce it reaches the uterus, zygote is now composed of 32 -50 ball of cell termed as a MORULA

7. Another 3-4 days, morula becomes a BLASTOCYST consisting of:An inner cell mass which will become the future embryoTrophoblast which will become the placenta and membranes

8. At approx 8-10 days after fertilization, blastocyst attaches to the endometriumSheds off last residues of corona radiata and zonapellucidaBrushes against endometrium (apposition) and settles downA slight vaginal bleeding is experienced during implantation stage because capillaries are ruptured by the implanting trophoblast cells

9. EMBRYONIC & FETAL STRUCTURESDECIDUA – uterus that has grown thick and vascular3 areasDeciduabasalis – lies directly under the embryo (portion where the trophoblast establish communication with maternal blood vessel)

10. Deciduacapsularis – portion that stretches or encapsulates the surface of the trophoblast

11. Deciduavera – the remaining portion of the uterine liningCHORIONIC VILLIMiniature villi similar to probing fingers that appear on the 11th or 12th day

12. They begin the formation of the placenta

13. Consists of a central core of connective tissue and fetal capillariesConsists of 2 layers of trophoblast cells:Syncytiotrophoblast(syncitial layer) – produces HCG, somatomammotropin (human placental lactogen), estrogen and progesteroneCytotrophoblast (middle or Langhan’s layer) – functions in early pregnancy to protect the growing embryo and fetus from infection (eg syphilis)

14. PLACENTA15-20CM IN DIAMETER, 2-3 CM DEEP, 400-600g at full term

15. Has 25-30 cotyledons (placental compartments that lie on the maternal side)

16. Has 2 sides

17. Maternal – dirty rough

18. Fetal – shiny smoothFUNCTIONS:Serves to conduct oxygen and nutrients for the fetus

19. Secretes endocrine hormones (syncytial cells)

20. hCG – 1st placental hormone - enusures corpus luteum to continuously produce progesterone and estrogen - supresses maternal immunologic reaction so that placental tissue is not detected and rejected as a foreign substance

21. - if fetus is male, stimulates the testes to begin producing testoterone - at 8 week, begins progesterone production, as a result, CL disintegrates and hCG production decreasesESTROGEN (estriol) – “hormone of women” - contributes to mammary gland development of mother in preparation for lactation - stimulates uterine growth to accommodate growing fetus

22. PROGESTERONE - “Hormone for Mothers” - necessary to maintain endometrial lining of the uterus during pregnancy - reduces contractility of uterus during pregnancy preventing preterm laborHUMAN PLACENTAL LACTOGEN (human chorionic somatomammotropin) - with both growth promoting and lactogenic (milk producing) properties - promotes mammary gland (breast) growth in preparation for lactation

23. - regulates maternal glucose, protein and fat levels so that adequate amounts of these are always available to the fetusAMNIOTIC FLUID800-1200ml

24. Slightly alkaline pH 7.2

25. Fetal urine adds to its volumeFunctions:Shields fetus against pressure or blow to the mother’s abdomen

26. Protects fetus from temperature change

27. Aids in muscular development because it allows fetus’ freedom to move

28. Protects the umbilical cord from pressure protecting fetal oxygen supplyHydramnios – excessive amniotic fluid - more than 2000ml or pockets of fluid larger than 8cm on UTZOligohydramnios – reduction in the amount of amniotic fluid - less than 300ml or no pockets of fluid larger than 1 cm on UTZ

29. AMNIOTIC MEMBRANESChorionic membrane – the outermost fetal membrane; purpose is to form a sac that contains the amniotic fluid

30. Amniotic membrane – 2nd membrane lining the chorionic membrane; forms beneath the chorion - produces amniotic fluid - produces phospholipid that initiates the formation of prostaglandins which can cause uterine contractions and may be the trigger that initiates labor

31. UMBILICAL CORDFormed from the amnion and chorion

32. 53cm (21 in) length; 2 cm thick

33. Wharton’s jelly – a gelatinous mucopolysaccharide that forms the bulk of the umbilical cord giving it its body; prevents pressure on the veins and arteries

34. Outer surface is covered with amniotic membrane

35. Composed of 1 vein (carrying blood from placental villi to the fetus) and 2 arteries (blood from fetus back to palcentalvilli)Blood flow is 350ml/min at term

36. Walls are with smooth muscles, no nerve supply

37. Function:

38. Transports oxygen and nutrients to the fetus from placenta and return waste products from fetus to placenta