Fertilization Process Quiz

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary purpose of capacitation in the fertilization process?

To allow sperm to penetrate the zona pellucida (correct)

To promote sperm formation

To enhance sperm motility

To initiate acrosome reaction

During the movement of sperm from the cervix to the oviduct, what assists their propulsion?

Muscle contractions of the uterus

Chemical signals from the oocyte

Fluid movements generated by uterine cilia (correct)

Cilia of the uterine tube

Which key event occurs during the acrosome reaction?

Exocytosis of the acrosome (correct)

Sperm membrane fusion with the oocyte

Activation of sperm motility

Sperm undergoes capacitation

What is a necessary condition for sperm to fertilize the oocyte?

They must be capacitated Signup and view all the answers

What happens to sperm motility upon reaching the isthmus during their journey?

Sperm become less motile Signup and view all the answers

What is the duration of capacitation that sperm must undergo before they can fertilize an oocyte?

Approximately 7 hours Signup and view all the answers

What is the zona pellucida?

The outer layer of the oocyte Signup and view all the answers

What triggers the acrosome reaction in sperm?

Interaction with zona proteins Signup and view all the answers

What is the primary function of the zona pellucida during fertilization?

It facilitates and maintains sperm binding. Signup and view all the answers

What enzyme is primarily released during the penetration of the zona pellucida?

Acrosin Signup and view all the answers

Which statement accurately describes the process of capacitation?

It refers to the process of sperm maturation that enhances motility. Signup and view all the answers

What initiates the acrosome reaction in sperm?

Contact with the oocyte membrane Signup and view all the answers

After the sperm binds to the zona pellucida, what happens to prevent further sperm penetration?

Alteration of the zona pellucida properties through lysosomal enzymes. Signup and view all the answers

Which phase of fertilization involves the sperm penetrating the zona pellucida?

Phase 2: penetration of the zona pellucida Signup and view all the answers

What changes occur in the zona pellucida once one spermatozoon successfully penetrates the oocyte?

Alteration of properties to prevent further penetration. Signup and view all the answers

What role do integrins on the oocyte play in fertilization?

They mediate initial adhesion of sperm to the oocyte. Signup and view all the answers

What happens to the oocyte membrane immediately after a spermatozoon enters?

It undergoes a structural change making it impenetrable to other spermatozoa. Signup and view all the answers

Which process describes the alteration of the zona pellucida to prevent further sperm binding?

Cortical reaction. Signup and view all the answers

What is the result of the spermatozoon entering the oocyte regarding the meiotic division?

It causes the oocyte to finalize its second meiotic division. Signup and view all the answers

What happens to the plasma membrane of the spermatozoon upon fusion with the oocyte membrane?

It is left behind on the surface of the oocyte. Signup and view all the answers

What is formed when the male pronucleus is created?

A diploid cell. Signup and view all the answers

What is the primary function of the activating factor from the spermatozoon?

It induces the cortical reaction in the oocyte. Signup and view all the answers

How do the maternal and paternal chromosomes contribute to the zygote after fertilization?

They restore the diploid number of chromosomes. Signup and view all the answers

Which of the following correctly describes the pronuclei after the sperm enters the oocyte?

Both are morphologically identical and upon growth replicate their DNA. Signup and view all the answers

Study Notes

Phases of Fertilization

Phase 1: Penetration of the Corona Radiata
- 200-300 million sperm deposited; only 300-500 reach fertilization site.
- Other sperm assist the fertilizing sperm in overcoming barriers.
- Capacitated sperm move through corona cells.
Phase 2: Penetration of the Zona Pellucida
- Zona pellucida plays a critical role in sperm binding and triggers the acrosome reaction.
- Binding mediated by zona protein (ZP3).
- Acrosomal enzymes (e.g., acrosin) enable sperm to penetrate zona pellucida.
- Sperm contact with the oocyte alters zona permeability.
- Release of lysosomal enzymes from oocyte cortical granules prevents further sperm penetration and alters zona properties, ensuring only one sperm can fertilize.
Phase 3: Fusion of Oocyte and Sperm Membranes
- Initial adhesion through integrins on the oocyte and disintegrins on sperm.
- Sperm fusion with the oocyte maintains compatibility for fertilization.

Fertilization Basics

Fertilization involves the fusion of male and female gametes.
Occurs in the ampullary region of the uterine tube.

Movement of Spermatozoa

1% of sperm deposited in the vagina reach the cervix.
Sperm rely on propulsion and fluid movement for migration to the oviduct, taking 2-7 hours.
Sperm become less motile at the isthmus but regain motility at ovulation due to chemo-attractants.

Capacitation

Process that prepares sperm for zona pellucida penetration.
Lasts approximately 7 hours, mostly in the uterine tube.
Involves the removal of glycoprotein and seminal plasma proteins from the sperm's membrane.

Acrosome Reaction

Exocytosis of the acrosome triggered by zona proteins.
Plasma membranes of sperm and oocyte fuse, allowing one spermatozoon to penetrate the oocyte.
Only the head and tail of the sperm enter the oocyte cytoplasm, leaving the plasma membrane on the oocyte’s surface.

Immediate Egg Responses Post-Fertilization

Cortical and zona reactions ensure the oocyte’s impermeability to additional sperm.
Resumption of second meiotic division occurs immediately, resulting in a second polar body and the definitive oocyte.
Activation factors from the sperm initiate metabolic processes in the egg.

Formation of Pronuclei

Sperm nucleus swells and forms the male pronucleus.
Male and female pronuclei are morphologically indistinguishable and eventually merge.

DNA Replication in Zygote

Each pronucleus (haploid) replicates its DNA, preparing for the diploid state.
23 maternal and 23 paternal chromosomes split, ensuring zygote receives a normal diploid chromosome number.

Results of Fertilization

Restoration of diploid chromosome number with half from each parent.
Creation of a genetically unique zygote.
Determination of the sex of the new individual based on chromosomal combination.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge on the phases of fertilization, including the critical role of enzymes like acrosin in penetrating the zona pellucida. This quiz covers the journey of sperm and the biological mechanisms involved in successful fertilization.