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Blastulation. 1 - morula, 2 - blastula.
First stages of segmentation of a fertilized mammalian ovum. Semidiagrammatic. z.p. Zona pellucida. Polar bodies. a. Two-cell stage. b. Four-cell stage. c. Eight-cell stage. d, e. Morula stage.
Gray's p.46
Days 3
Precursor Zygote
Gives rise to Blastula, Blastocyst
Code TE E2.

A morula (Latin, morus: mulberry) is an embryo at an early stage of embryonic development, consisting of cells (called blastomeres) in a solid ball contained within the zona pellucida.[1]

The morula is produced by embryonic cleavage, the division of the zygote. Once the zygote has divided into 16 cells, it begins to resemble a mulberry, hence the name morula (Latin, morus: mulberry).[2] Within a few days after fertilization, cells on the outer part of the morula become bound tightly together with the formation of desmosomes and gap junctions, becoming nearly indistinguishable. This process is known as compaction.[3][4] Compaction provides adaptive benefits for various species, including Copidosoma floridanum; in the morula-stage, C. floridanum embryo invades the embryo of the host, utilizing adherent junctions to host cells. The cells of the morula then secrete a viscous liquid[specify], causing a central cavity to be formed, forming a hollow ball of cells known as the blastocyst.[5][6] The blastocyst's outer cells will become the first embryonic epithelium (the trophectoderm). Some cells, however, will remain trapped in the interior and will become the inner cell mass (ICM), and are pluripotent. In mammals (except monotremes), the ICM will ultimately form the "embryo proper", while the trophectoderm will form the placenta and other extra-embryonic tissues. However, reptiles have a different ICM. The stages are longer and divided in 4 parts.[7][8][9][10]

See also[edit]


  1. ^ Boklage, Charles E. (2009). How New Humans Are Made: Cells and Embryos, Twins and Chimeras, Left and Right, Mind/Self/Soul, Sex, and Schizophrenia. World Scientific. p. 217. ISBN 978-981-283-513-0. 
  2. ^ Sherman, Lawrence S. et al., ed. (2001). Human embryology (3rd ed.). Elsevier Health Sciences. p. 20. ISBN 978-0-443-06583-5. 
  3. ^ Chard, Tim & Lilford, Richard (1995). Basic sciences for obstetrics and gynaecology. Springer. p. 18. ISBN 978-3-540-19903-8. 
  4. ^ Mercader, Amparo et al. (2008). "Human embryo culture". In Lanza, Robert & Klimanskaya, Irina. Essential stem cell methods. Academic Press. p. 343. ISBN 978-0-12-374741-9. 
  5. ^ Patestas, Maria Antoniou & Gartner, Leslie P. (2006). A textbook of neuroanatomy. Wiley-Blackwell. p. 11. ISBN 978-1-4051-0340-4. 
  6. ^ Geisert, R.D. & Malayer, J.R. (2000). "Implantation: Blastocyst formation". In Hafez, B. & Hafez, Elsayed S.E. Reproduction in farm animals. Wiley-Blackwell. p. 118. ISBN 978-0-683-30577-7. 
  7. ^ Morali, Olivier G. et al. (2005). "Epithelium-Mesenchyme Transitions are Crucial Morphogenetic Events Occurring During Early Development". In Savagner, Pierre. Rise and fall of epithelial phenotype: concepts of epithelial-mesenchymal transition. Springer. p. 16. ISBN 978-0-306-48239-7. 
  8. ^ Birchmeier, Carmen et al. (1997). "Morphogenesis of epithelial cells". In Paul, Leendert C. & Issekutz, Thomas B. Adhesion molecules in health and disease. CRC Press. p. 208. ISBN 978-0-8247-9824-6. 
  9. ^ Nagy, András (2003). Manipulating the mouse embryo: a laboratory manual. CSHL Press. pp. 60–61. ISBN 978-0-87969-591-0. 
  10. ^ Connell, R.J. & Cutner, A. (2001). "Basic Embryology". In Cardozo, Linda & Staskin, David. Textbook of female urology and urogynaecology. Taylor & Francis. p. 92. ISBN 978-1-901865-05-9. 

Further reading[edit]