A morula (Latin "morus", mulberry) is an embryo at an early stage of embryonic development, consisting of approximately 12-32 cells (called blastomeres). The morula is produced by embryonic cleavage, the rapid cell division of the zygote. The morula is a solid ball of cells; the inner blastomeres are called the "inner cell mass" and the blastomeres on the surface are called the "outer cell mass." The blastomeres change their shape and tightly align themselves against each other to form a compact ball of cells. This is called compaction and is likely mediated by cell surface adhesion glycoproteins.

In mammals the morula travels to the uterus around 3-4 days after fertilization, and at about 4 days after fertilization a fluid-filled space called the blastocystic cavity appears and the morula becomes a "blastocyst."

Cloning | Embryology | Developmental biology

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