Fertilization - Mammalian Development

Question 1

What steps lead up to fertilization?

Answer 1

1. Oocyte Meiosis - completes Meiosis 1 and commences Meiosis 2 (arrests at Metaphase II).
2. Spermatozoa Capacitation - following release (ejaculation) and mixing with other glandular secretions, activates motility and acrosome preparation.
3. Migration - both Oocyte and Spermatozoa.
   i. oocyte ovulates and is released from ovary into fimbria and then into uterine tube
   ii. spermatozoa is ejaculated, then deposited in vagina, then the tail swims into uterine tube to fertilize oocyte.

Question 2

What happens during fertilization?

Answer 2

1. Spermatozoa penetrates the zone pellucida (ZP) of the mature oocyte formed from ovulation of oogonia.
2. Spermatozoa swims around the perivitelline space (PVS).
3. Spermatozoa hits the first polar body (1pb).
4. Spermatozoa binds to the oocyte membrane.
5. Second polar body is forced out and the fertilization cone forms.

Now the egg is fertilized.

Question 3

What is the fertilization cone?

Answer 3

A conical projection protruded from the surface of certain eggs at the point of contact with the fertilizing sperm when the second polar body protrudes outward.

Question 4

What is the purpose of the zona pellucida?

Answer 4

1. glycoprotein shell
2. mechanical protection of egg
3. involved in the fertilization process
4. allows the sperm to bind
5. blocks polyspermy

Question 5

What are the key properties of the fertilized egg at the end of fertilization?

Answer 5

1. the egg has fertilized and is now at its one cell stage embryo.
2. It is also referred to as the Zygote.
3. Zona Pellucida is still present