Question

Germinal layer formed from trophoblast of mammalian blastocyst is
A. Ectoderm
B. Endoderm
C. Mesoderm
D. None of the above

Answer 1

Hint: he zygote undergoes cleavage after fertilisation to form a blastula. The blastula, which is a hollow cell ball, goes through a process of gastrulation, through which the three germ layers form. The trophoblast gives rise to the placenta.

Complete answer:
The development of multicellular species starts with a single-celled zygote, which goes through rapid cell division, called a cleavage to form a hollow cell ball known as blastula.

The blastula forms the blastocyst during the next stage of development. The cells in the blastula are organised into two layers: the inner cell and the outer trophoblast layer. The inner cell mass will begin to form the embryo. Trophoblast secretes enzymes that allow the blastocyst to be incorporated into the uterine endometrium. The trophoblast will then form the placenta to provide nourishment to the embryo.

The cells in the blastula are then spatially rearranged to form three cell layers. This phase is called gastrulation. During gastrulation, the blastula folds in and the cells move to create the three layers of cells in the framework, the gastrula, with an empty area that becomes the digestive tract. Each layer of cells is called a germ layer that can be divided into various organ systems.

Thus, the correct answer is option” D” i.e., None of the above

Note: The endoderm, ectoderm, and mesoderm are the three germ layers. The cells in each germ layer differentiate to form tissues and embryonic organs. The ectoderm gives rise to the nervous system and the epidermis, and other tissues. Mesoderm results in the formation of nerve cells and connective tissue. The endoderm gives birth to the gut and to several internal organs.