Glossary · Definition · v2026.3
What Is a Morula?
A morula is a solid ball of cells formed approximately three to four days after fertilization when the embryo has undergone several rounds of cleavage division, typically containing 16 or more cells.
Clinical significance
The morula stage represents a transition between cleavage-stage development and blastocyst formation. Embryos that fail to compact into a morula often arrest before reaching the blastocyst stage.
Common confusion
The morula is sometimes confused with a blastocyst, but it lacks the fluid-filled cavity and cell differentiation characteristic of the blastocyst stage.
Related reference
Used in
This content defines terminology for educational orientation. It does not constitute medical advice.
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