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Human morula (day 2)[1]
Human morula (day 3)[1]

(Latin, morula = mulberry) An early stage in post-fertilization development when cells have rapidly mitotically divided to produce a solid mass of cells (12-15 cells) with a "mulberry" appearance. This stage is followed by formation of a cavity in this cellular mass blastocyst stage.

A key event prior to morula formation is "compaction", where the 8 cell embryo undergoes changes in cell morphology and cell-cell adhesion that initiates the formation of this solid ball of cells.

In humans, morula stage of development occurs during the first days in the first week following fertilization and is described as Carnegie stage 2. This stage is followed by formation of a cavity, the blastocoel, which defines formation of the blastocyst.

ART Preimplantation blastomere biopsy
ART Preimplantation blastomere biopsy[2]

In Assisted Reproductive Technology, the morula stage is when one of the earliest prenatal diagnostic test can be carried out, by removing a single cell (blastomere) and carrying out genetic diagnosis on its DNA.
Links: Carnegie stage 2 | Morula | Mitosis | Blastocyst | Fertilization | Week 1 | Category:Carnegie Stage 2 | Category:Morula

Some Recent Findings

  • Functional genomics of 5- to 8-cell stage human embryos by blastomere single-cell cDNA analysis[3] "Forty-nine blastomeres from 5- to 8-cell human embryos have been investigated following an efficient single-cell cDNA amplification protocol to provide a template for high-density microarray analysis. The previously described markers, characteristic of Inner Cell Mass (ICM) (n = 120), stemness (n = 190) and Trophectoderm (TE) (n = 45), were analyzed, and a housekeeping pattern of 46 genes was established. ...In summary, the global single-cell cDNA amplification microarray analysis of the 5- to 8-cell stage human embryos reveals that blastomere fate is not committed to ICM or TE."
  • Non-invasive imaging of human embryos before embryonic genome activation predicts development to the blastocyst stage[4] "We report studies of preimplantation human embryo development that correlate time-lapse image analysis and gene expression profiling. By examining a large set of zygotes from in vitro fertilization (IVF), we find that success in progression to the blastocyst stage can be predicted with >93% sensitivity and specificity by measuring three dynamic, noninvasive imaging parameters by day 2 after fertilization, before embryonic genome activation (EGA)."
More recent papers
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This table shows an automated computer PubMed search using the listed sub-heading term.
  • Therefore the list of references do not reflect any editorial selection of material based on content or relevance.
  • References appear in this list based upon the date of the actual page viewing.

References listed on the rest of the content page and the associated discussion page (listed under the publication year sub-headings) do include some editorial selection based upon both relevance and availability.

Links: References | Discussion Page | Pubmed Most Recent | Journal Searches

Search term: Morula Development

Gang Li, Nannan He, Haixia Jin, Yan Liu, Yihong Guo, Yingchun Su, Yingpu Sun The Influence of Single Nucleotide Polymorphism Microarray-Based Molecular Karyotype on Preimplantation Embryonic Development Potential. PLoS ONE: 2015, 10(9);e0138234 PubMed 26381524

Jenna Kropp, Hasan Khatib mRNA fragments in in vitro culture media are associated with bovine preimplantation embryonic development. Front Genet: 2015, 6;273 PubMed 26379701

Julian Marcos, Sonia Pérez-Albalá, Amparo Mifsud, Marta Molla, Jose Landeras, Marcos Meseguer Collapse of blastocysts is strongly related to lower implantation success: a time-lapse study. Hum. Reprod.: 2015; PubMed 26355116

Gemma Fabozzi, Alessandra Alteri, Emilia Rega, Maria Flavia Starita, Claudio Piscitelli, Pierluigi Giannini, Antonio Colicchia Morphological assessment on day 4 and its prognostic power in selecting viable embryos for transfer. Zygote: 2015;1-8 PubMed 26350430

J Norhazlin, M N K Nor-Ashikin, B P Hoh, S H Sheikh Abdul Kadir, S Norita, M Mohd-Fazirul, W J Wan-Hafizah, D Razif, M H Rajikin, B Abdullah Effect of DNase treatment on RNA extraction from preimplantation murine embryos. Genet. Mol. Res.: 2015, 14(3);10172-84 PubMed 26345954


Model embryo to 32 cell stage icon.jpg
 ‎‎Morula Model
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Mouse zygote division icon.jpg
 ‎‎Zygote Mitosis
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Mouse zygote division 02 icon.jpg
 ‎‎Early Division
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Parental genome mix 01 icon.jpg
 ‎‎Parental Genomes
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Mouse blastocyst movie icon.jpg
 ‎‎Mouse Blastocyst
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  • E-cadherin mediated adhesion initiates at compaction at the 8-cell stage
  • regulated post-translationally via protein kinase C and other signalling molecules

Blastomere Division

Spindle orientation calculation.[5]

An in vitro study of human blastocyst development[6] showed that those blastomeres that initially divide quickly are more likely to develop to blastocyst stage.

A recent study in mice showed that there was no specific orientation of the mitotic spindle during cell division in the 8 to 16 cell stage transition.[5] This suggests no predetermined cleavage pattern (pre-patterned) at the 8 cell stage and only modulated by the extent of cell rounding up during mitosis. In other species, such as the worm C.elegans and ascidians, have specific patterns of spindle orientation from the zygote stage.

Model Human Morula Development

The following figure is from a recent study[4] using video and genetic analysis of in vitro human development during week 1 following fertilization.

Model human blastocyst development.jpg

  • EGA - embryonic genome activation
  • ESSP - embryonic stage–specific pattern, four unique embryonic stage–specific patterns (1-4)
Links: Figure with legend

Morulas in Other Species

Mouse Morula

Links: Mouse Development

Sea Urchin Morula

Sea Urchin- early embryo cleavage pattern.jpg

Sea Urchin early embryo cleavage pattern (SDB Gallery Images)

Links: Sea Urchin Development

Bovine Morula

Bovine morula 01.jpg

Bovine Morula[7]

  • Image shows DNA staining (white) and f-actin filaments (orange) at day 4. Scale bars represent 100 µm.
  • Pale staining round nuclei are at interphase.
  • Arrow shows single nucleus at prophase.
  • A single nucleus is seen at metaphase.
  • Condensed bright nuclei are apoptotic.

Links: Bovine Development | Mitosis


  1. 1.0 1.1 Pu Zhang, Marco Zucchelli, Sara Bruce, Fredwell Hambiliki, Anneli Stavreus-Evers, Lev Levkov, Heli Skottman, Erja Kerkelä, Juha Kere, Outi Hovatta Transcriptome profiling of human pre-implantation development. PLoS ONE: 2009, 4(11);e7844 PubMed 19924284 | PMC2773928 | PLoS One
  2. Tanya Milachich New advances of preimplantation and prenatal genetic screening and noninvasive testing as a potential predictor of health status of babies. Biomed Res Int: 2014, 2014;306505 PubMed 24783200 | PMC3982254 | Biomed Res Int.
  3. Galán A, Montaner D, Póo ME, Valbuena D, Ruiz V, Aguilar C, Dopazo J, Simón C. Functional genomics of 5- to 8-cell stage human embryos by blastomere single-cell cDNA analysis. PLoS One. 2010 Oct 26;5(10):e13615. PMID21049019 | PLoS One.
  4. 4.0 4.1 Connie C Wong, Kevin E Loewke, Nancy L Bossert, Barry Behr, Christopher J De Jonge, Thomas M Baer, Renee A Reijo Pera Non-invasive imaging of human embryos before embryonic genome activation predicts development to the blastocyst stage. Nat. Biotechnol.: 2010, 28(10);1115-21 PubMed 20890283 | Nat Biotechnol.
  5. 5.0 5.1 Nicolas Dard, Sophie Louvet-Vallée, Bernard Maro Orientation of mitotic spindles during the 8- to 16-cell stage transition in mouse embryos. PLoS ONE: 2009, 4(12);e8171 PubMed 19997595 | PLoS One.
  6. J Fenwick, P Platteau, A P Murdoch, M Herbert Time from insemination to first cleavage predicts developmental competence of human preimplantation embryos in vitro. Hum. Reprod.: 2002, 17(2);407-12 PubMed 11821286
  7. Sandra Leidenfrost, Marc Boelhauve, Myriam Reichenbach, Tuna Güngör, Horst-Dieter Reichenbach, Fred Sinowatz, Eckhard Wolf, Felix A Habermann Cell arrest and cell death in mammalian preimplantation development: lessons from the bovine model. PLoS ONE: 2011, 6(7);e22121 PubMed 21811561 | PLoS One.


Bette J Dzamba, Karoly R Jakab, Mungo Marsden, Martin A Schwartz, Douglas W DeSimone Cadherin adhesion, tissue tension, and noncanonical Wnt signaling regulate fibronectin matrix organization. Dev. Cell: 2009, 16(3);421-32 PubMed 19289087

Joana Santos, C Filipe Pereira, Aida Di-Gregorio, Thomas Spruce, Olivia Alder, Tristan Rodriguez, Véronique Azuara, Matthias Merkenschlager, Amanda G Fisher Differences in the epigenetic and reprogramming properties of pluripotent and extra-embryonic stem cells implicate chromatin remodelling as an important early event in the developing mouse embryo. Epigenetics Chromatin: 2010, 3;1 PubMed 20157423

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Cite this page: Hill, M.A. (2015) Embryology Morula. Retrieved October 5, 2015, from

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© Dr Mark Hill 2015, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G