Final answer:
During weeks 13-16 of fetal development, sensory organ development includes eye and ear formation, blinking and sucking motions, hair growth on the scalp, and development of the excretory system with well-formed kidneys and accumulation of meconium in the intestines.
Step-by-step explanation:
Fetal Development: Weeks 13-16
During weeks 13-16 of fetal development, several critical developments occur. One of the key changes is in the area of sensory organ development. The eyes, which previously were positioned on the sides of the head, move closer together and start exhibiting blinking motions, despite remaining sealed shut. The formation of the lips advances to where they show sucking motions, which is crucial for feeding after birth.
The ears undergo significant changes as well, moving upward on the head and lying flatter against the head, representing advanced development. Additionally, the scalp commences to grow hair, which is an early stage of the fetus's hair development. Furthermore, this period is critical for the excretory system; the kidneys become well-formed, and meconium starts to gather in the intestines, a substance comprising ingested amniotic fluid, cellular debris, mucus, and bile.