Trace the events from copulation to zygote formation in a human female.

Question : Trace the events from copulation to zygote formation in a human female.

 

The correct answer is –

i) During copulation (coitus) semen is released by the penis into the
vagina (insemination).

ii) The motile sperms swim rapidly, pass through the cervix, enter into
the uterus and finally reach the ampullary region of the fallopian
tube.

iii) The ovum released by the ovary is also transported to the ampullary
region where fertilization takes place.

iv) Fertilizations can only occur if the ovum and sperms are transported
simultaneously to the ampullary region. This is the reason why not
all copulations lead to fertilizations and pregnancy.

v) The process of fusion of a sperm with an ovum is called fertilizations.

vi) During fertilizations, a sperm comes in contact with the zona pellucida
layer of the ovum and induces changes in the membrane that block
the entry of additional sperms. Thus, it ensures that only one sperm
can fertilise an ovum.

vii) The secretions of the acrosome help the sperm enter into the
cytoplasm of the ovum through the zona pellucida and the plasma
membrane.

viii) This induces the completion of the meiotic division of the secondary
oocyte.

ix) The second meiotic division is also unequal and results in the
formation of a second polar body and a haploid ovum (ootid).

x) Soon the haploid nucleus of the sperms and that of the ovum fuse
together to form a diploid zygote.