Fertilization

The final aim of all love intrigues, be they comic or tragic, is really of more importance than all other ends in human life. What it turns upon is nothing less than the composition of the next generation. A. Schopenhauer as quoted by Charles Darwin, 1871

Fertilization This lecture lecture introduces you to the beginning of development – fertilization, or the conception of a new individual. You will learn about the union of the spermatozoon and oocyte to form the zygote – the new individual. This is a fascinating process that involves a coordinated series of events leading to union of a single sperm with the egg. After this lecture you should be able to: • Describe the sequential series of events that accompany the fertilzation process. • Describe the contribution of the spermatozoon to the fertilization process. • Describe the contribution of the oocyte to the fertilization process.

17

Concepts in Fertilization Why fertilization?

Problems that must be dealt with Sperm entry

Prevention of polyspermy

Fertilization strategies

Transportation of gametes in humans

E m b r y o l o g y 18

L e c t u r e

M a n u a l

b y

M a r k

N i e l s e n

F e r t i l i z a t i o n

Fertilization Stages The process of conception

Capicitation of the sperm

Removal of glycoprotein coat and seminal proteins Where? How? Results

Penetration of the corona radiata Acrosome reaction

Tubal mucosal enzymes

Tail action of sperm

19

Penetration of the zona pellucida Acrosomal enzymes

Zona reaction

Membrane fusion and oocyte response Intracellular release of calcium ions

Wave-like movement of calcium ions Fast block

Oocyte response to calcium wave Cortical granule reaction (slow block)

Numerous metabolic reactions

Formation of ootid

Sperm decondensation and formation of male pronucleus

Completion of 2nd meiotic division – formation of female pronucleus

Emergence of zygote

Fusion of the pronuclei

Initiation of cleavage

E m b r y o l o g y 20

L e c t u r e

M a n u a l

b y

M a r k

N i e l s e n