1. Developed by D. Ann Currie
Fetal Development
Developed by
D. Ann Currie

2. Oogenesis Ovary gives rise to oogonial cells.
Cells develop into oocytes.
Meiosis begins and stops before birth.
Cell division resumes at puberty.
Development of Graafian follicle.

3. Ovum The female gamete are called Ovum.
The ovum are considered fertile for about hours after ovulation.

4. Spermatogenesis Production of sperm First meiotic division:
Primary spermatocyte replicates and divides.
Second meiotic division:
Secondary spermatocytes replicate and divide.
Produce four spermatids.

5. Sperm The male gamete are Sperm.
The sperm can survive in the female reproductive tract for hours.
However they are believed to be healthy and highly fertile for only 24 hours.
In a single ejaculation the male deposits approximately million sperm in the vagina. Only hundreds of sperm actually reach the ampulla. Only one sperm fertilizes the ovum.

7. FErtilization Fertilization occurs: when the sperm and ovum unite.
in the ampulla of the fallopian tube.

8. Changes to Sperm Capacitation: Acrosomal reaction:
Removal of plasma membrane and glycoprotein coat
Loss of seminal plasma proteins
Acrosomal reaction:
Release of enzymes
Allows entry through corona radiata

9. Ferilization

10. After Sperm Entry Zone pellucida blocks additional sperm from entering
Secondary oocyte completes second meiotic division
Forms nucleus of ovum
Nuclei of ovum and sperm unite
Membranes disappear
Chromosomes pair up

12. At the moment of fertilization the sex of the zygote is determined.
Female have XX (sex chromosomes)
Male have XY ( sex chromosomes)

13. Fertilization and cell division

14. Cell Division

16. Implantation(Nidation)
Zygote moves through the fallopian tube towards the cavity of the uterus.
Transportation takes 3 or more days.
Rapid mitotic divisions called cleavage is occurring.
7-10days after fertilization the blastocyst implants.
Most frequent site of attachment is the upper part of the posterior uterine wall.

17. Primary Germ Layers Primary germ layers: Ectoderm Mesoderm Endoderm
About days after conception
Primary germ layers:
Ectoderm
Mesoderm
Endoderm

18. Placenta Development Chorionic villi form spaces in decidua basalis
Spaces fill with maternal blood.
Chorionic villi differentiate:
Syncytium: outer layer
Cytotrophoblast: inner layer
Anchoring villi form septa

19. Placenta

25. Placenta Function Nutrition Excretion Fetal respiration
Production of fetal nutrients
Production of hormones
Large molecular compounds can not crossthe placenta
Other see text

26. Umbilical Cord Body stalk fuses with embryonic portion of the placenta
Provides circulatory pathway from chorionic villa to the embryo
Delivers oxygenated blood to the fetus:
One Vein
Returns waste material to maternal circulation:
Two Arteries

28. Fetal Environment Amnion: Encloses the amniotic cavity
The inner membrane that forms about the
2nd week of embryonic development
Forms a fluid-filled sac that surrounds the embryo and later the fetus.
Chorion:
Is the outer membrane
Becomes vascularized and forms the fetal portion of the placenta.

29. Amniotic Fluid Consists of 800-1200 ml by the end the pregnancy
Surrounds, cushions, protects, the fetus and allows for fetal movement.
Maintains body temperature of the fetus.
Contains fetal urine and is a measurement of fetal kidney function.
The fetus modifies the amniotic fluid through the processes of swallowing, urinating, and movement trough respiratory tract.
Other see text.

30. Pre-embryonic First 2 week after conception Cleavage
Blastomeres form morula
Blastocyst:
- develops into embryonic disc and amnion
Trophoblast:
- develops into chorion

31. Embryonic Period
Beginning at Day 15 through approximately the 8th week after conception.

32. Fetal Period
Week 9 after conception to birth

33. Fetal Development Week 4
Beginning development of GI tract
Heart is developing
Somites develop—beginning vertebrae
Heart is beating and circulating blood
Eyes and nose begin to form
Arm and leg buds are present

35. Fetal development Week 12
Eyelids are closed
Tooth buds appear
Fetal heart tones can be heard
Genitals are well-differentiated
Urine is produced
Spontaneous movement occurs

36. Fetal development Week 16
Lanugo begins to develop
Blood vessels are clearly developed
Active movements are present
Fetus makes sucking motions
Swallows amniotic fluid
Produces meconium

37. Fetal Development: Week 20
Subcutaneous brown fat appears
Quickening is felt by mother
Nipples appear over mammary glands
Fetal heartbeat is heard by fetoscope

38. Fetal Development: Week 24
Eyes are structurally complete
Vernix caseosa covers skin
Alveoli are beginning to form

39. Featl Development: Week 32
Rhythmic breathing movements
Ability to partially control temperature
Bones are fully developed but soft and flexible
Variability seen on FHR monitor

40. Fetal Development: Week 36
Increase in subcutaneous fat
Lanugo begins to disappear

41. Fetal Development: Week 38
Skin appears polished
Lanugo has disappeared except in upper arms and shoulders
Hair is now coarse and approximately 1 inch in length
Fetus is flexed

42. Twins Fraternal: two ova and two sperm
Identical: single fertilized ovum
- Originate at different stages

43. Fetal Circulation Umbilical Cord Fetal Heart Rate-110-160 BPM
Ductus venosus
Ductus arteriosus
Foramen ovale

45. The end of this presentation but the beginning of a new life….