Question

Stage of embryo development at which implantation occurs in human female is

• A. Morula
• B. Neurula
• C. Blastocyst
• D. Zygote

Answer 1

The correct option is C Blastocyst

Embryo development
Embryo development refers to the development and formation of embryos. It involves the following six stages:
1.Fertilisation - Zygote
2.Cleavage
3.Morula
4.Blastocyst
5.Gastrula
6.Neurula

Zygote
The fusion of the haploid sperm with the haploid ovum is known as fertilisation which results in the formation of diploid zygote. It is formed in the fallopian tube.

Morula
The embryo with 8 -16 blastomeres is called morula. It is formed in the fallopian tube.

Blastocyst
A blastocyst is a ball of cells with a large, fluid-filled cavity called blastocoel.

• The morula divides to form a blastocyst which consists of 200 - 300 cells. The blastomeres in the blastocyst are arranged into an outer envelope called trophoblast and inner mass of cells (attached to the trophoblast) called inner cell mass.
• The trophoblast layer helps in the implantation of blastocyst in the uterine wall and gives rise to extra-embryonic membranes.
• The inner mass gets differentiated as an embryo.

Implantation
In the uterine wall, the embryonic stage called blastocyst gets embedded by a process called implantation.

Neurula
Neurula is the embryonic stage in which the neural plate is formed by the ectoderm. Neural plate eventually forms the brain and spinal cord.