Fertilisation in Humans

What is the primary function of the granules released from the cortex of the egg during fertilization?

Which process occurs concurrently with the entry of a sperm cell into the egg?

What happens to the nuclei after the sperm and egg have fused?

What is formed after the paternal and maternal chromosomes attach to the mitotic spindle?

What is polyspermy and how is it prevented during fertilization?

What is the primary function of capacitation in sperm cells?

Which enzyme is crucial for a sperm cell to penetrate the corona radiata?

During the acrosomal reaction, what is released to aid the penetration of the zona pellucida?

What event occurs after the sperm cell fuses with the oocyte membrane?

Which process occurs first during fertilization?

What is the end result of the union of haploid gametes?

Fertilisation in Humans

Definition: The union of haploid gametes (sperm and ovum) results in the formation of a diploid zygote.
Location: Fertilization occurs primarily in the oviduct (fallopian tube).

Stages of Fertilisation

Capacitation:
- Enhancements in sperm due to secretions in the female reproductive tract.
- Leads to increased sperm motility.
- Involves the removal of glycoproteins and plasma proteins from the sperm surface, enhancing interaction with the egg.
Acrosomal Reaction:
- Fusion of the acrosome membrane with the sperm's cell surface membrane.
- Release of acrosomal enzymes, such as hyaluronidase and protease, upon contact with the secondary oocyte.
- Hyaluronidase enables the sperm to penetrate the corona radiata.
Spermic Entry:
- Upon reaching the zona pellucida (extracellular matrix of the egg), hydrolases are released to facilitate sperm penetration.

Cortical Reaction

Occurs post-fusion of the sperm and egg plasma membranes.
Release of enzymes from cortical granules in the egg.
Enzymatic reaction hardens the zona pellucida, preventing polyspermy (multiple sperm entry).

Meiosis and Zygote Formation

As the sperm enters the egg, the secondary oocyte completes meiosis II, resulting in the ovum and the second polar body.
Fusion of paternal and maternal chromosomes occurs, leading to the formation of a zygote ready for its first cell division.

Explore the complex process of human fertilisation, including the stages of capacitation, acrosomal reaction, spermic entry, and the cortical reaction. Understand the role of each stage in the formation of a diploid zygote and where fertilisation primarily occurs.