At the end of the embryonic period (eighth week of development), all of the major external features (ears, eyes, mouth, upper and lower limbs, fingers, and toes) are formed and the major organ systems are nearing completion.
||Neural tube, primitive body cavities and cardiovascular system form
||Heart is beating; upper limb buds and primitive ears visible; lower limb buds and primitive eye lenses appear shortly after ears
||Brain develops rapidly; head grows disproportionately; hand plates develop
||Limb buds differentiate noticeably; retinal pigment accentuates eyes
||Limbs differentiate rapidly
||Embryo appears human; external ears are visible; fingers, toes lengthen; external genitalia are visible, but are not distinctly male or female