Fertilisation in Humans

Questions and Answers

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

To form a protective barrier against multiple sperm (correct)

To assist in the completion of meiosis II

To facilitate the fusion of sperm and egg

To enhance the motility of the sperm

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

The paternal chromosomes are duplicated

Meiosis I is completed in the egg

The secondary oocyte completes meiosis II (correct)

The zygote undergoes its first cell division

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

They immediately merge into one nucleus

They dissolve completely

They remain separate until the first cell division (correct)

They disperse before fertilization is complete

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

A diploid zygote Signup and view all the answers

What is polyspermy and how is it prevented during fertilization?

The fertilization of an egg by multiple sperm; prevented by hardening of the zona pellucida. Signup and view all the answers

What is the primary function of capacitation in sperm cells?

To increase sperm motility Signup and view all the answers

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

Hyaluronidase Signup and view all the answers

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

Hydrolytic enzymes Signup and view all the answers

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

Cortical reaction Signup and view all the answers

Which process occurs first during fertilization?

Capacitation Signup and view all the answers

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

A diploid zygote Signup and view all the answers

Study Notes

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.

Description

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.