Cleavage & Formation of Blastocyst MCQ - Practice Questions with Answers

Updated on Sep 18, 2023 18:34 AM

Quick Facts

Embryonic Development: Cleavage & Formation of Blastocyst is considered one of the most asked concept.
25 Questions around this concept.

Which one of the following statements about morula in humans is correct?

It has almost equal quantity of cytoplasm as an uncleaved zygote but much more DNA

It has far less cytoplasm as well as less DNA than in an uncleaved zygote

It has more or less equal quantity of cytoplasm and DNA as in uncleaved zygote

It has more cytoplasm and more DNA than an uncleaved zygote

A change in the amount of yolk and its distribution in the egg will affect it's

Pattern of cleavage

Number of blastomeres produced

Fertilization

Formation of zygote

Embryonic Development: Cleavage & Formation of Blastocyst

The mitotic division starts as the zygote moves through the isthmus of the oviduct called cleavage towards the uterus and forms 2, 4, 8, 16 daughter cells called blastomeres.
When the blastomeres divide completely the cleavage is called holoblastic cleavage.
The embryo with 8 to 16 blastomeres is called a morula.
The embryo gradually becomes a 64-celled structure.
A cavity is now formed within the cell mass. This cavity is called the blastocyst cavity or blastocoel.
The embryo is now termed the blastocyst.
The blastocyst is made up of an outer layer of cells called the trophoblast or trophectoderm and an inner cell mass or embryoblast.
The trophoblast layer then gets attached to the endometrium and the inner cell mass gets differentiated as the embryo.

Significance of Cleavage:

Cleavage distributes the cytoplasm of the zygote amongst the blastomeres.
It allows for morphogenetic movements necessary for cell differentiation, germ layer formation and tissue and organ formation.
It converts the unicellular zygote into a multicellular embryo.