Fertilization is the process by which a sperm cell and an egg cell unite to form a zygote, which eventually develops into an embryo. It is a vital step in sexual reproduction and involves various physiological mechanisms.
1. Process of Fertilization: Fertilization typically occurs in the fallopian tubes of the female reproductive system. The process can be divided into several steps:
- Maturation of the Egg: During each menstrual cycle, one egg (ovum) is released from an ovary and travels down the fallopian tube. The released egg is surrounded by protective layers called the zona pellucida and corona radiata.
- Sperm Journey: Millions of sperm cells are ejaculated during sexual intercourse. They need to swim through the , cervix, and uterus to reach the fallopian tubes where the egg is present.
- Penetration and Recognition: Only a few hundred sperm cells reach the egg. The sperm swim through the zona pellucida and corona radiata until one sperm cell successfully penetrates the egg membrane. This process is facilitated by specific proteins on the sperm surface and receptor molecules on the egg.
- Fusion of Genetic Material: Once a sperm enters the egg, the outer layer of the egg undergoes changes that prevent other sperm from entering. The nucleus of the sperm fuses with the nucleus of the egg, resulting in the combination of their genetic material to form the zygote.
2. Sperm Activation: Sperm cells are initially immotile and need to undergo a process called capacitation to become capable of fertilizing an egg. During capacitation, the sperm undergo various physiological changes, including increased flagellar motility and changes in the outer membrane.
3. Egg Activation: Once fertilized, the egg undergoes a process called egg activation. This involves a series of biochemical and electrical changes in the egg's cytoplasm to prepare it for embryo development. Activation includes the release of calcium ions, resumption of the cell cycle, and the prevention of polyspermy (entry of multiple sperm cells).
4. Pre-implantation: After fertilization, the zygote starts dividing through a process called cleavage, resulting in a ball of cells called a blastocyst. The blastocyst then travels down the fallopian tube to the uterus, where it implants into the uterine lining.
Overall, the physiology of fertilization involves a complex interplay of numerous molecular and cellular events that ensure successful fusion of genetic material and initiation of embryo development.
phsiology of fertilization?
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