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

• fish knife
• fish ladder
• fish loaf
• fish louse
• fish lure
• fish meal
• fish mousse
• fish oil
• fish scale
• fish slice
• fish species
• fish steak
• fish stew
• fish stick
• fish tank
• fish-liver oil
• fish-worship
• fishbone
• fishbowl
• fisher
• fisher cat
• fisherman
• fisherman's bend
• fisherman's knot
• fisherman's lure