1. After intercourse, sperm are deposited in the vagina near the cervix while the ovum is picked up by the fallopian tubes. 2. The sperm and ovum travel through the fallopian tubes, with the sperm taking 48-72 hours and the ovum taking 12-24 hours to complete their journey. 3. Fusion of a single sperm and a mature ovum occurs in the ampulla of the fallopian tube to form a zygote, initiating embryonic development and restoring the chromosomal number of the species.

1. TARANJEET KAUR
B.Sc. Nursing

2. APPROXIMATION OF GAMETES
 The semen on intercourse gets deposited deep in
the vagina at the opening of external os of cervix .
 Ovum is picked up by the fimbrae by muscular
/suction/cililary/positive chemotaxis action .
 Life span of ovum is 12-24 hrs whereas that of
sperm is 48-72 hrs.
 It liquefies within 20 minutes & thousands of
sperms swim up through cervical mucous following
3 minutes into the uterine cavity &100 -300 reach
the outer 3rd of fallopian tube within 5 minutes .

3.  Process of fusion of a single spermatozoa
with a mature ovum at ampulla of
fallopian tube to form zygote.
 Objectives are :
 To initiate embryonic development of egg,
 To restore chromosomal number of species

4.  Chemical action of hayluronidase released by acrosomal
cap of sperm head called capacitation causes complete
dissolution of cells of corona radiata .
 Zona pellucida has sperm receptors (ZP1,ZP2,ZP3) only
a single sperm enter ovum by physically drilling a hole ,
proteolytic digestion of pathway.
 Oolema block occurs to prevent further entry of sperms.
 Second Meiotic division of oocyte takes place each
containing haploid number of chromosomes 23 X ,
bigger one is female pronucleus & smaller is 2nd
polar body.
 Head & neck of sperm become male pronucleus
containing haploid number chromosomes (23 X, 23 Y).

6.  1st Meiotic division leads two cell stage
within 24-30 hrs, zygote now called as
blastomeres ,each contain equal volume &
chromosome number.
 Blastomeres continue to divide by binary
division through 4 ,8 ,16 cell stage.
 The morula stage : 16-64 cell stage ,
reaches uterine cavity after 4th day of
fertilization.

7.  On day 4th morula floats in uterine cavity
going through development formation of
200 cells & fluid filled cavity occurs called
blastocyst.
 At one pole of blastocyst there is a
compact mass of cells formed called inner
cell mass.
 A single layer of cells formed around
outside of blastocyst known as
trophoblast.

9. THANK