1. Membranous structure that functions as the circulatory system in mammalian embryos until the heart becomes functional
   - yolk sac, umbilical vesicle, vesicula umbilicus

Derived forms: vitelline sacs

Type of: sac

• choroid plexus
• choroid vein
• choroidal artery
• choropleth map
• chortle
• chorus
• chorus frog
• chorus girl
• chorus line
• chosen
• chosen people
• chou
• Chou dynasty
• Chou En-lai
• chough
• chouse
• chicken Marengo
• chicken mousse
• chicken out
• chicken paprika
• chicken paprikash
• chicken provencale
• chicken purloo
• chicken roundworm
• chicken run