The waxy, protective substance secreted by fetal sebaceous glands that coats and moisturizes the skin is called:

1. During weeks 16-20 of fetal development, the skin needs protection from prolonged exposure to amniotic fluid. 2. Sebaceous glands secrete a substance that coats the skin for this purpose. 3. This substance is called vernix caseosa. 4. Lanugo, by contrast, is the fine silky hair that also covers the skin during this period, a separate structure from the waxy coating. 5. Meconium is fetal stool accumulating in the intestines, and surfactant is a lung substance, so neither is a skin coating. 6. So vernix caseosa is correct. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 28 "Development and Inheritance", p.1340 §Other Organ Systems_