Terminology related with general embryology

Terminology related to general embryology

Gestational period: The whole gestation period is subdivided into three stages:

a)       Germinal period : it extends from 1^st to 3^rd week of development

b)       Embryonic period : it extends from the 4^th to 8^th week

c)       Foetal period: it extends from the third month up to termination of pregnancy  

Oocyte: the female germ or sex cell produced in the ovaries

Sperm: the male germ cell produced in the testes.

Blastocyst : after the morula enters the uterus from the uterine tube , a fluid filled cavity –  the blastocyst cavity –develops inside it . This change converts the morula into a blastocytes

Implantation: the process during which the blastocyst attaches to the endometrium and subsequently embeds in it. It occurs at 6 days after fertilization.

Gastrulation : formation of three layered embryonic germ disc

Embryo:   the developing human during its early stages of development. It extends to the end of the eighth week

Conceptus: the embryo and its adnexa or associated membranes

Fetus: after the embryonic period the developing human is called a fetus.

Gemetogenesis: it is the process of formation and development of male and female gametes

Zygote: Definition:this cell formed by the union of an oocyte and a sperm during fertilization

Cleavage: is a series of mitotic divisions that results in an increase in cells, blastomeres, which become smaller with each division.

Morula : the 12-16 cell stage of the early embryo at 3 days post conception

Menopause: the permanent cessation of the menses

Length of the pregnancy: from 1^st day of last menstrual period: 280 days or 40 weeks

                                            After fertilization: 266 days or 38 weeks

Embryonic period /period of organogenesis: most major organ and organs systems are formed during the third to eighth weeks and this period is called embryonic period or period of organogenesis.

Growth: means increase in bulk which takes place by cells division, increasing cell size or increased accumulation of intercellular substance

Differentiation: is a complicated process in which groups of cells assume special characteristics and functions

Totipotent cells: are able to produce a separate embryo under favorable conditions

Pluripotent cells: are groups of cells which produce specific type of tissue