embryonic stage

in human prenatal development, the roughly 6-week period in which the three-layered embryo (gastrula) develops. The embryonic stage follows the 2-week germinal stage and precedes the fetal stage, which begins in the 3rd month of pregnancy. The term is, however, sometimes used to refer to the full first 8 weeks of pregnancy.

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Psychology term of the day

December 22nd 2024

retinal image

the inverted picture of an external object formed on the retina of the eye. The resolution of the image varies with the diameter of the pupil, the focus becoming sharper as illumination of the object increases and the aperture of the pupil decreases.