A
morula (
LatinLatin is an Italic language originally spoken in Latium and Ancient Rome. Through the Roman conquest, Latin spread throughout the Mediterranean and a large part of Europe...
"morus",
mulberryMorus or Mulberry is a genus of 10–16 species of deciduous trees native to warm temperate and subtropical regions of Asia, Africa, Europe, and the Americas, with the majority of the species native to Asia....
) is an
embryoAn embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
at an early stage of embryonic development, consisting of
cellsThe cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of an organism that is classified as living, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos...
(called
blastomereA blastomere is a type of cell produced by division of the egg after fertilization.-Human blastomere:In humans, blastomere formation begins immediately following fertilization and continues through the first week of embryonic development. About 30 hours after fertilization, the zygote divides into...
s) in a solid ball contained within the
zona pellucidaThe zona pellucida is a glycoprotein membrane surrounding the plasma membrane of an oocyte. It is a vital constitutive part of the latter, external but not extraneous to it...
.
Production
The morula is produced by
embryonic cleavageIn embryology, cleavage is the division of cells in the early embryo. The zygotes of many species undergo rapid cell cycles with no significant growth, producing a cluster of cells the same size as the original zygote. The different cells derived from cleavage are called blastomeres and form a...
, the rapid
divisionMitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets in two daughter nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two daughter cells containing...
of the
zygoteA zygote , or zygocyte, is the initial cell formed when a new organism is produced by means of sexual reproduction. A zygote is synthesized from the union of two gametes, and constitutes the first stage in a unique organism's development...
. After reaching the 16-cell stage, the cells of the morula differentiate. The inner blastomeres will become the
inner cell massIn early embryogenesis of most eutherian mammals, the inner cell mass is the mass of cells inside the primordial embryo that will eventually give rise to the definitive structures of the fetus...
and the blastomeres on the surface will later flatten to form the
trophoblastTrophoblasts are cells forming the outer layer of a blastocyst, which provide nutrients to the embryo and develop into a large part of the placenta...
. As this process begins, 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.
Development
In mammals the morula travels to the
uterusThe uterus is a major female hormone-responsive reproductive sex organ of most mammals, including humans. It is within the uterus that the fetus develops during gestation. The term uterus is used consistently within the medical and related professions; the Germanic term, womb is more common in...
around 3–4 days after fertilization, and at about 4 days after fertilization a fluid-filled space called the blastocoel cavity appears and the morula becomes a
blastocystThe blastocyst is a structure formed in the early embryogenesis of mammals, after the formation of the morula, but before implantation. It possesses an inner cell mass , or embryoblast, which subsequently forms the embryo, and an outer layer of cells, or trophoblast, which later forms the placenta...
.