Developed byD. Ann Currie

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

12-24 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 48-72 hours. However they are believed to be healthy

and highly fertile for only 24 hours.

In a single ejaculation the male deposits approximately 200-500 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 10-14 days after conceptionPrimary germ layers:

EctodermMesodermEndoderm

Chorionic villi form spaces in decidua basalisSpaces fill with maternal blood.Chorionic villi differentiate:

Syncytium: outer layerCytotrophoblast: inner layer

Anchoring villi form septa

http://www.medgadget.com/archives/img/placenta.GIF

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 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.

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.

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 8th 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-110-160 BPM Ductus venosus Ductus arteriosus Foramen ovale