Definition of terms

Embryology: study of developmental process from a single cell to a baby in months

Embryogenesis: formation and development of an embryo

Ontogeny: Process of development of an organism

Conceptus: Product of conception

Cleavage: series of mitotic cell divisions of the zygote resulting in blastomeres

Morula: a mass of 12 to 32 blastomeres

After a while, the morula develops a cavity and we call it a;

Blastocyst: structure formed after a cavity forms within the morula.

Blastocele: fluid that enters the cavity of blastocyst


Embryoblast: inner cell mass of blastocyst

Trophoblast: outer cell mass of blastocyst

Endometrium: inner epithelial lining of the uterus

Implantation: attachment and embedding of the blastocyst to the endometrium

Decidua: endometrium during pregnancy

Bilaminar disc: 2 layered embryo, occurs during second the 2nd week

Gastrula: trilaminar disc embryo (3 layered embryo)

ie. ectoderm, mesoderm, endoderm

Gastrulation: process of formation of the trilaminar disc, begins on 15th day

Neurulation: process of formation of neural tube, the primordium of the central nervous system

Primordium: beginning or first discernible indication of an organ or structure

Organogenesis: formation of body organs

Morphogenesis: process of shape development

Fetus: unborn offspring

Abortion: expulsion of an embryo or fetus before its viability (capable of living outside the uterus)

Teratology: study of birth defects

Teratogen: an agent that causes congenital (born with) defects

Anomaly: structural abnormality

Malformation: abnormal developmental process

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