The document summarizes key events in human pregnancy, including fertilization, implantation, formation of the placenta, and childbirth. It notes that fertilization occurs when a sperm fertilizes an egg in the fallopian tubes. The fertilized egg then implants in the uterus 6-8 days later, burrowing into the endometrium and beginning formation of the placenta and embryo. By the end of the first month, the embryo's blood is exchanging nutrients and waste with the mother's blood via chorionic villi. Childbirth begins with labor, as hormones cause the uterus to contract in three stages - cervical dilation, expulsion of the baby, and discharge of the placenta.

1. Ms.Anu Sebastian: B.Pharm; M.Pharm
Assistant Professor,
Dept. Of Pharmacology
Nirmala College Of Pharmacy
Muvattupuzha,Ernakulam,Kerala

2.  Pregnancy occurs once an ovum is successfully fertilized & successfully implants.
Events leading to fertilization
 Sperm swims from the vagina through the cervix, through the uterine wall until it
reaches the oocyte in the uterine tubes.
 When burrows into the Zona pellucida of the oocyte enzymes digest it .Way to allow
the sperm to reach the egg.
 The plasma membranes fuse & sperm nucleus enters the oocyte’s cytoplasm.
 This initiates the cortical reaction in which the egg destroys other sperm receptors,so
no other sperm binds & fertilizes the egg.
 When the male & female chromosomes come together fertilization has been
completed & the zygote will begin to divide.
 Once it is large enough & has formed a blastocyst , it reaches the uterus to implant.

3. Implantation
 6-8 days after fertilization the blastocyst implants as it burrows into the
endometrium.
 At this point some cells will become the developing embryo and some the
placenta.
 As the trophoblast burrow into the endometrium it causes bleeding (about
10-12 days after fertilization)
Formation of the placenta
 The embryonic tissues form finger like projection called chorionic villi that
come in contact with the area of the bleeding endometrium(lacunae).

4.  The embryo connect to the chorionic villi via the body stalk
which will become the future umbilical cord.
 By the end of the first month the embryo’s blood is in close
contact with the mother’s blood & exchange of nutrients &
waste is happening at the chorionic villi.
 At the start of the 4th month the endometrium & the
chorionic villi make a thick disc called placenta.This is the
site where nutrient & waste exchange occur.After childbirth
the placenta detaches from the uterus.

5. Parturition/Childbirth
 Labor is the events prior to childbirth
 When the fetus grows so much that the placenta cannot meet its nutritional needs, stress
hormones are release to signal the beginning of labor.
 Oxytocin & prostaglandins cause the uterus to contract.
Stages of labor:
 Dilation stage: begins when the uterus first contracts & ends when cervix
dilates(10cm).Cervical dilation can take 6-12 hours.
 Expulsion stage: from the time the cervix is fully dilated until the child leaves the mother’s
womb. These are strong placental contractions, this process can take up to 12 hours.
 Placental stage: Uterine contractions discharge the placenta.

6. THANK YOU