Formation of the blastocoel is an important step in development — it sets the stage for future growth and change in the cells of the early embryo. Learn how the blastocoel helps and protects these cells.
The Blastocoel — A Great Place to Hang Out
We’ve all heard the expression ‘man cave.’ You know, a place to do guy things, get some salty snacks and beverages — a place to get through the things guys have to get through. You probably didn’t know that an embryonic cell cave exists, but it’s one of the most important structures in the newly-developing fertilized egg and it’s called the blastocoel.
The word part coel (pronounced seel) comes from Greek, meaning cavity, or cave. The process that forms the blastocoel is even called cavitation: the creation of a cave. This special fuid filled space starts forming on about the fifth day after fertilization in the tiny ball of cells that will become a new creature.
It’s a fully functional cell cave — full of food and drink and good things to help the future embryo cells grow and get through the the stuff a new life has to get through.
Change is Everywhere
The formation of this blastocoel begins when the early dividing cells of the recently fertilized egg begin to differentiate. This is when they become specialized, as they move around and start to form a new space where there used to be solid cells. These changes, and the presence of the blastocoel, mark the blastula stage of development, which in mammals is called a blastocyst.
This movement happens because water passes freely through cell membranes, and by osmosis, it’ll flow out or in depending on where the least concentration of water is. If there is more salt in the fluid outside a cell compared to the inside, then water will flow out of the cell (because there is less water outside).The fluid in the blastocoel is like the best sports drink: good for any growth and change of the embryoblast cells inside the blastula. There is sugar, growth factors, and proteins: all things that make it possible for differentiation to keep happening are in there.This is a good thing because these cells need the extra energy.
In fact, in mammals an extra form of energy production, or metabolism, is turned on just to provide the needs of the cells that are changing so quickly and working hard to form the blastocoel.
After all the growth and change of the blastula stage, the blastocoel also helps to serve another purpose.
At this point cells are changing all over again and movement will be happening everywhere: internal structures are starting to form. The fluid cushion of the blastocoel will make the movement possible, and it will eventually form a layer of fluid between new cell layers that will lead to the digestive tract as the next stage, the gastrula, begins.
The blastocoel is a fluid filled cavity, or space, in the developmental stage known as the blastula, which in mammals is called a blastocyst.
The process of formation is called cavitation, and it begins from cells differentiating, or becoming specialized, and moving to different regions of the blastula.Outer cells are called trophoblast, which seal off the outside of the blastula and provide nutrients, salts, and fluid to the blastocoel cavity. These aid in the growth and change of the cells in the blastocoel that will become the embryo. When the blastula stage is ending, the blastocoel provides support for structural movement and becomes a fluid layer as part of the developing digestive tract.