Germ (signpost)

The embryonic period includes the first 8 weeks of intrauterine development, during which individual parts of the body differentiate and the foundations of organs and body systems are formed.

Embryo development:
 * 1st week – fertilization and nesting of the egg;
 * 2nd week – the embryo has 2 layers of cells;
 * 3rd week – the first missed period in the mother, the embryo has 3 layers of cells;
 * 4th week – the embryo already has a human form, the neural tube closes, the bases of the limbs are formed, the embryo measures 4–5 mm;
 * 5th week – the initial mouth and the bases of the fingers are formed;
 * 6th week – the primary nose and palate are formed, the embryo measures 21–23 mm;
 * 7th week – the foundation of the eyelids is formed;
 * 8th week – distinct gonads appear (testes or ovaries).


 * First week of embryo development.
 * Second week of embryo development.
 * Third week of embryo development.
 * Fourth to eighth week of embryo development.

Related Articles

 * Prenatal period: Embryo • Fetus