Title: Fetal Development – Anatomy and Physiology
Headings: Fetal Development
Fetal Development
Learning Objectives
Sexual Differentiation
The Fetal Circulatory System
Other Organ Systems
Interactive Link Questions
Critical Thinking Questions
Glossary
ductus arteriosus

Content: The eyes are well-developed by this stage, but the eyelids are fused shut. The fingers and toes begin to develop nails. By the end of week 12, the fetus measures approximately 9 cm (3.5 in) from crown to rump. Weeks 13–16 are marked by sensory organ development. The eyes move closer together; blinking motions begin, although the eyes remain sealed shut. The lips exhibit sucking motions. The ears move upward and lie flatter against the head. The scalp begins to grow hair. The excretory system is also developing: