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

• Epinephelus adscensionis
• Epinephelus fulvus
• epinephrin
• epinephrine
• epineurium
• Epipactis
• Epipactis gigantea
• Epipactis helleborine
• Epipaleolithic
• epiphany
• Epiphany of Our Lord
• epiphenomenon
• epiphora
• epiphyllum
• epiphyseal
• epiphysial
• epiphysis
• epiphysis cerebri
• epiphyte
• epiphytic
• epiphytic plant
• epiphytotic
• epiplexis
• Epipremnum
• Epipremnum aureum