Study of Blastula Stages in Mammals

Our Objective

To study the blastula stage of embryonic development in mammals, with the help of permanent slide. 


The Theory 

Cleavage and Blastula Stage 

The development of multi-cellular organisms begins from a single-celled zygote, which undergoes rapid cell division to form the blastula. The rapid, multiple rounds of cell division are termed cleavage. Blastula or blastomeres is a hollow sphere of cells, produced during the development of an embryo by repeated cleavage of a fertilized egg.  

The blastula is usually a spherical layer of cells that is blastoderm which  surrounding a fluid-filled or yolk-filled cavity called as the blastocoel. Mammals at this stage form a structure called the blastocyst, which is characterized by an inner cell mass that is distinct from the surrounding blastula. 

Here the cells in the blastula arrange themselves in two layers: the inner cell mass, and an outer layer called the trophoblast. The inner cell mass is also known as the embryoblast and this mass of cells will go on to form the embryo. Each cell within the blastula is called a blastomere.  

At the stage of development, the inner cell mass consists of embryonic stem cells that will differentiate into the different cell types needed by the organism. The trophoblast will contribute to the placenta and nourish the embryo. 

Learning Outcomes

  • Students can understand the concept of the formation of an embryo.
  • Students understand the steps involved in formation of blastula.
  • Students will learn the discrete stages of cleavage which leads to the formation of the blastula.