Fertilization_Process_in_Mammals.power point

fertilization in mammals

1. Fertilization Process in Mammals Certificate Level Biology Notes

2. Definition Fertilization is the union of a male gamete (sperm) and a female gamete (ovum) to form a zygote, marking the beginning of a new organism.

3. Site of Fertilization In mammals, fertilization occurs in the fallopian tube, specifically in the ampulla region. This area provides optimal temperature, pH, and nutrients for gamete interaction.

4. Conditions Necessary for Fertilization - Release of a mature ovum (ovulation) - Presence of viable sperm in the female tract - Sperm survival and motility - Proper timing and favorable environment in the oviduct

5. Step 1: Sperm Transport Sperm are ejaculated into the vagina during copulation. They travel through the cervix and uterus to the fallopian tube with the help of flagellar movement and uterine contractions. Only a few reach the oviduct.

6. Step 2: Capacitation of Sperm Sperm undergo biochemical changes in the female tract (capacitation), making them capable of fertilizing the egg. Their membranes become more permeable, and motility increases.

7. Step 3: Ovulation and Egg Transport The mature ovum is released from the ovary and swept into the fallopian tube by cilia. It is surrounded by the corona radiata and zona pellucida.

8. Step 4: Sperm–Egg Recognition Sperm bind to receptors on the zona pellucida. Only sperm of the same species can successfully attach and proceed.

9. Step 5: Acrosome Reaction The acrosome releases enzymes (hyaluronidase, acrosin) that digest the egg coverings, allowing sperm penetration.

10. Step 6: Fusion of Sperm and Egg Membranes Sperm head and midpiece enter the egg cytoplasm; the tail remains outside. Chemical changes prevent entry of additional sperm.

11. Step 7: Block to Polyspermy The cortical reaction releases enzymes that harden the zona pellucida and destroy sperm receptors, ensuring only one sperm fertilizes the egg.

12. Step 8: Activation of the Egg The sperm’s entry stimulates the egg to complete meiosis II, forming a mature ovum and second polar body.

13. Step 9: Fusion of Pronuclei The male and female pronuclei fuse to form a diploid zygote with complete genetic material.

14. Step 10: Formation of the Zygote The zygote is the first cell of the new organism. It begins to divide and develop into an embryo.

15. Events After Fertilization - Cleavage (cell division) - Blastocyst formation - Implantation in the uterine wall - Embryo and placenta development

16. Importance of Fertilization - Restores diploid chromosome number - Determines genetic makeup and sex - Initiates embryo development - Ensures species continuity

17. Summary Flow Chart Sperm Transport → Capacitation → Ovulation → Sperm–Egg Contact → Acrosome Reaction → Fusion → Block to Polyspermy → Fusion of Nuclei → Zygote Formation → Cleavage → Implantation