Fertilisation (Word Version)

Fertilisation
Ji Keon LOOI

What needs to happen preceeding fertilisation?
•Da Vinci's Renaissance sketch showed that semen came down from a man's brain through a channel in his spine.

How does your sperm look like?
•The little preformed person in the sperm. An imaginary representation of what a sperm might look like, if able to be seen clearly, drawn by Nicolaus Hartsokeker in Essai de ditropique, 1694.

Fertilisation
•The process of fusion between the male and the female gametes in the ampullary region of the uterine tube

•Spermatozoa must undergo
–Capacitation
–Acromsome reaction
before it is able to fertilise the oocyte

Fertilisation
Phases of fertilisation
•Phase 1
–Penetration of the corona radiata

•Phase 2
–Penetration of the zone pellucida

•Phase 3
–Fusion of the oocyte and sperm cell membranes

Three ways a fertilised oocyte will respond:-
•Cortical and zona reactions
–Release of cortical oocyte granules
–Impenetrable oocyte membrane to other spermatozoa
–Zona pellucida alters its struc and composition to prevent sperm binding and penetration

•Resumption of the second meiotic division
–Second polar body (receives no cytoplasm)
–Definitive oocyte has 22+X chromosome (female pronucleus)

•Metabolic activation of the egg
–Activating factor from spermatozoon
–Early embryogenesis

The main results of fertilisation
•Restoration of the diploid number of chromosomes
–½ from father, ½ from mother
–Diploid zygote

•Determination of the sex
–XX / XY

•Initiation of cleavage
–Forms blastomere à morula à blastocyst


Clinical correlations (to be expanded)
•Contraception techniques
•Infertility
•IVF
•GIFT (Gamete infrafallopian transfer)

Thank you
•Langman’s Medical Embryology 10th Edn