Final answer:
Human fetuses develop fingers and toes between 28 and 54 days after conception through a process of tissue separation. By the eighth week, major brain structures and facial features develop, and the fetus is approximately 3 cm in size.
Step-by-step explanation:
During the sixth week of development, the distal ends of the upper and lower limb buds expand and flatten into a paddle shape. This region will become the hand or foot. Within the paddle, areas of tissue undergo cell death, producing separations between the growing fingers and toes. By week 7, the facial structure includes nostrils, outer ears, and lenses. By the eighth week, the head is nearly as large as the rest of the embryo's body, and major brain structures are in place. By the end of the embryonic period, the fetus is approximately 3 cm from crown to rump and weighs approximately 8 g.