1. Membranous structure that functions as the circulatory system in mammalian embryos until the heart becomes functional
   - vitelline sac, umbilical vesicle, vesicula umbilicus 
2. Membranous structure enclosing the yolk of eggs in birds, reptiles, marsupials, and some fishes; circulates nutrients to the developing embryo

Derived forms: yolk sacs

Type of: sac

Encyclopedia: Yolk sac

• rotor shaft
• rotoscope
• rotovator
• rotted
• rotten
• rotten borough
• rottenly
• rottenness
• rottenstone
• rotter
• Rotterdam
• rotting
• Rottweiler
• rotund
• rotunda
• rotundity
• rotundly
• rotundness
• roturier
• rouble
• rouge
• rouge et noir
• rouge plant
• rougeberry
• rouged