Final answer:
In human embryological development, limb buds initially form, then elongate, and by the sixth week, differentiate to outline future bones with mesenchyme forming hyaline cartilage. In the seventh week, limbs rotate to reach their final position.
Step-by-step explanation:
The human embryological limb development involves the formation of four surfaces and edges. Initially, during the fourth week of development, limb buds appear, which will give rise to the arms and legs. The outer part, or the apical ectodermal ridge, stimulates the elongation of the limb. By the sixth week, the limb bud expands and flattens at the distal end into a paddle shape, which further divides into fingers and toes due to selective cell death. Within these limb buds, mesenchyme differentiates into hyaline cartilage, creating the primitive models for the bones of the upper and lower limbs. In the seventh week, an important event is the rotation of the limbs: the upper limbs rotate laterally, and the lower limbs rotate medially, establishing their final orientation.