Summary
A hollow ball of cells formed by cleavage, containing a fluid-filled cavity.
In depth
In mammals, the blastocyst has an outer trophoblast (forms placenta) and an inner cell mass (forms embryo) around a blastocoel. The blastocyst implants around day 6 to 7.
Blastocoel formation depends on fluid pumped by trophoblast cells. Inner cell mass cells are pluripotent. Hatching from the zona pellucida precedes implantation.
Example: IVF embryos are often transferred at blastocyst stage.
The blastula is a hollow sphere of cells enclosing a fluid-filled cavity called the blastocoel, formed after about 128 cells in a frog or sea urchin. In placental mammals the equivalent is the blastocyst, with an outer trophoblast and an inner cell mass.
The trophoblast forms the placenta, while the inner cell mass gives the embryo proper and is the source of embryonic stem cells. The blastocyst hatches from the zona pellucida and implants in the uterine wall about six to seven days after fertilisation.
Example: IVF embryos are usually transferred at the blastocyst stage.
Key idea: the blastula prepares cells for the movements of gastrulation.
Frequently asked questions
What is Blastula?
A hollow ball of cells formed by cleavage, containing a fluid-filled cavity.
Which area of biology covers Blastula, and how advanced is it?
Blastula is one of the 54 topics in Developmental Biology. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Embryo, Totipotency, Pluripotency.
Can you give an example of Blastula?
Embryonic stem cells are derived from the inner cell mass.
What should I learn before Blastula?
Blastula is a Beginner topic, so no earlier topic is required. Other Beginner topics in Developmental Biology that pair well with it include Fertilisation, Zygote, Embryo.
What topics are related to Blastula?
The closest topics to Blastula are Embryo, Totipotency, Pluripotency, Cleavage. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Blastula?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Blastula. To practise the whole of Developmental Biology, use the Developmental Biology quiz.
How is Blastula different from Embryo?
Blastula: A hollow ball of cells formed by cleavage, containing a fluid-filled cavity. Embryo: The early developmental stage of an organism produced by division of the zygote. Read both side by side and note what each one explains.
How should I study Blastula step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Embryo and explain the difference aloud. Finally, take the Developmental Biology quiz and come back to this page for any question you miss.