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Developed b y D. Ann Currie 2012

 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.

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

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

 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.

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

 Capacitation: ◦ Removal of plasma membrane and glycoprotein coat ◦ Loss of seminal plasma proteins  Acrosomal reaction: ◦ Release of enzymes ◦ Allows entry through corona radiata

 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

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

 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.

About days after conception Primary germ layers: Ectoderm Mesoderm Endoderm

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

 Nutrition  Excretion  Fetal respiration  Production of fetal nutrients  Production of hormones  Large molecular compounds can not crossthe placenta  Other see text

 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

 Amnion:  Encloses the amniotic cavity  The inner membrane that forms about the  2 nd 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.

 Consists of 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.

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

 Beginning at Day 15 through approximately the 8 th week after conception.

 Week 9 after conception to birth

 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

 Eyelids are closed  Tooth buds appear  Fetal heart tones can be heard  Genitals are well-differentiated  Urine is produced  Spontaneous movement occurs

 Lanugo begins to develop  Blood vessels are clearly developed  Active movements are present  Fetus makes sucking motions  Swallows amniotic fluid  Produces meconium

 Subcutaneous brown fat appears  Quickening is felt by mother  Nipples appear over mammary glands  Fetal heartbeat is heard by fetoscope

 Eyes are structurally complete  Vernix caseosa covers skin  Alveoli are beginning to form

 Rhythmic breathing movements  Ability to partially control temperature  Bones are fully developed but soft and flexible  Variability seen on FHR monitor

 Increase in subcutaneous fat  Lanugo begins to disappear

 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

 Fraternal: two ova and two sperm  Identical: single fertilized ovum - Originate at different stages

 Umbilical Cord  Fetal Heart Rate BPM  Ductus venosus  Ductus arteriosus  Foramen ovale

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