Morula

Morula is an early stage embryo consisting of cells (known as blastomeres) in a solid ball contained within the Zona pellucida. This stage occurs after cleavage but before the blastula stage. The term is derived from the Latin word for mulberry, morula, which the mass of cells is said to resemble.

Development

The morula is produced by a series of cleavage divisions of the zygote, which is a single-cell organism that results from the fertilization of an ovum by a sperm. These cleavage divisions are mitotic divisions that occur without growth, producing a larger number of smaller cells. Each of these cells, now known as blastomeres, contains a copy of the zygote's genome.

The morula stage is typically reached two to three days post-fertilization. At this point, the embryo is a compact mass of 16 to 32 cells. The cells on the outside of the morula form tight junctions with each other, creating a seal that prevents the passage of molecules between them. This allows the inside of the morula to become a closed system, leading to the formation of a fluid-filled cavity, the blastocoel, and the next stage of development, the blastula.

Clinical significance

The morula stage is important in the context of in vitro fertilization (IVF). In IVF, embryos are typically cultured until they reach the blastocyst stage, at which point they are transferred to the uterus. However, some embryos may be transferred at the morula stage. The success of IVF procedures can be influenced by the quality of the morula, with better outcomes associated with more evenly sized blastomeres and fewer fragments.

See also

• Blastocyst
• Embryogenesis
• Zygote

References

Morula Resources
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