Biology, asked by letslear2006, 4 months ago

with the well labelled diagram explain fertilization in humans


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Answered by sanoharlal1
0

Answer:

Fertilization and implantation are the most critical events in the reproduction process. In this process, both egg and sperm are fused together to form a zygote. Later it gets implanted into the uterus and the development of an organism.

Let us have a look at how fertilization in humans takes place.

Fertilization and Implantation

Fertilization in Humans

“Fertilization in humans refers to the fusion of male and female gametes that facilitates the development of a new organism.”

Answered by loks13
0

Answer:

Steps of Fertilization in Humans

The fertilization process in humans takes place in several stages involving both the chemical and physical events. The different stages of fertilization in humans are mentioned below:

Acrosomal Reaction

The sperms incapacitation undergo acrosomal reactions and release certain chemicals known as sperm lysins present in the acrosome.

Due to the acrosomal reactions, the plasma membrane of the secondary oocyte and the sperm are fused together so that the contents of the sperms can enter. When the plasma membrane of the sperm binds with that of the secondary oocyte, the plasma membrane of the oocyte depolarizes. This prevents polyspermy.

Calcium ions play a significant role in the acrosomal reaction. The main factors essential for acrosomal reactions are optimum pH, temperature and calcium and magnesium concentration.

Cortical Reaction

Soon after the fusion of the plasma membranes, the oocyte shows cortical reactions. Cortical granules found under the plasma membrane of the oocyte, which fuses with the plasma membrane and releases cortical enzymes between the zona pellucida and plasma membrane. The zona pellucida is hardened by the cortical enzymes that prevent polyspermy.

Sperm Entry

A projection known as the cone of reception is formed by the secondary oocyte at the point of sperm contact. This cone of reception receives the sperm.

Karyogamy

After the entry of the sperm, the suspended second meiotic division is completed by the secondary oocyte. This gives rise to a haploid ovum and a second polar body.

The head of the sperm containing the nucleus detaches from the entire sperm and is known as male pronucleus. The tail and the second polar body degenerates. The nucleus of the ovum is known as female pronuclei.

The male and female pronuclei fuse and their nuclear membranes degenerate. The fusion of the chromosomes of male and female gametes is called karyogamy. The ovum is now fertilized and is known as a zygote.

Activation of Eggs

The entry of sperm triggers the metabolism in the zygote. Consequently, protein synthesis and cellular respiration increase.

Implantation

Once fertilization happens, the cell starts to divide and multiply within 24 hours in the fallopian tube. This detached multi-celled structure is called a zygote. Later, after 3-4 days it travels to the uterus and now we call it as an embryo.

The embryo develops and undergoes various stages and gets attached to the endometrial layer of the uterus. This process of attachment is known as implantation.  

 

Sex Determination

Fertilization is the process in which a new cell is formed when two gametes (sex cells) –sperm and ova fuse together. During this unbiased event, all genetic information is transferred from both the parents to their child and the gender of the child is determined.

Father determines the sex of the child, i.e. if the sperm carries a Y chromosome, the child will be a boy and if sperm carries X chromosome child will be a girl.

Hope it helps yu!

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