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Developed by D. Ann Currie

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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….

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