Presentation on theme: "Developed by D. Ann Currie"— Presentation transcript:
1Developed by D. Ann Currie Fetal DevelopmentDeveloped byD. Ann Currie
2Oogenesis 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.
3Ovum The female gamete are called Ovum. The ovum are considered fertile for about hours after ovulation.
4Spermatogenesis Production of sperm First meiotic division: Primary spermatocyte replicates and divides.Second meiotic division:Secondary spermatocytes replicate and divide.Produce four spermatids.
5Sperm 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.
7FErtilization Fertilization occurs: when the sperm and ovum unite. in the ampulla of the fallopian tube.
8Changes to Sperm Capacitation: Acrosomal reaction: Removal of plasma membrane and glycoprotein coatLoss of seminal plasma proteinsAcrosomal reaction:Release of enzymesAllows entry through corona radiata
10After Sperm Entry Zone pellucida blocks additional sperm from entering Secondary oocyte completes second meiotic divisionForms nucleus of ovumNuclei of ovum and sperm uniteMembranes disappearChromosomes pair up
16Implantation(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.
17Primary Germ Layers Primary germ layers: Ectoderm Mesoderm Endoderm About days after conceptionPrimary germ layers:EctodermMesodermEndoderm
18Placenta Development Chorionic villi form spaces in decidua basalis Spaces fill with maternal blood.Chorionic villi differentiate:Syncytium: outer layerCytotrophoblast: inner layerAnchoring villi form septa
25Placenta Function Nutrition Excretion Fetal respiration Production of fetal nutrientsProduction of hormonesLarge molecular compounds can not crossthe placentaOther see text
26Umbilical Cord Body stalk fuses with embryonic portion of the placenta Provides circulatory pathway from chorionic villa to the embryoDelivers oxygenated blood to the fetus:One VeinReturns waste material to maternal circulation:Two Arteries
28Fetal Environment Amnion: Encloses the amniotic cavity The inner membrane that forms about the2nd week of embryonic developmentForms a fluid-filled sac that surrounds the embryo and later the fetus.Chorion:Is the outer membraneBecomes vascularized and forms the fetal portion of the placenta.
29Amniotic 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.
30Pre-embryonic First 2 week after conception Cleavage Blastomeres form morulaBlastocyst:- develops into embryonic disc and amnionTrophoblast:- develops into chorion
31Embryonic PeriodBeginning at Day 15 through approximately the 8th week after conception.
33Fetal Development Week 4 Beginning development of GI tractHeart is developingSomites develop—beginning vertebraeHeart is beating and circulating bloodEyes and nose begin to formArm and leg buds are present