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

Type of: sac

• latch
• latch on
• latchet
• latchkey
• latchkey child
• latchstring
• late
• late blight
• Late Greek
• Late Latin
• late purple aster
• late-blooming
• late-flowering
• late-night hour
• late-ripening
• late-spring-blooming
• latecomer
• lated
• lateen
• lateen sail
• lateen-rig
• lateen-rigged
• lately
• latency
• latency period