Question

Upper limb development begins 2 to 4 days _____ lower limb development.

1) before
2) after
3) alongside
4) simultaneously

Answer 1

Upper limb development commences 2 to 4 days before lower limb development, with both starting as limb buds in the fourth week of embryonic development.

Step-by-step explanation:

Upper limb development begins 2 to 4 days before lower limb development. The upper limb bud first appears near the end of the fourth week of embryonic development, with the lower limb bud developing shortly thereafter. Both limbs initially develop as a small bulge known as a limb bud on the lateral side of the embryo. Following their appearance, limb buds undergo significant changes, including the rotation of the limbs and the formation of the handplate or footplate. By understanding these developmental processes, students grasp how the lower limb development lags slightly behind the upper limb development.