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

• lacrimation
• lacrimator
• lacrimatory
• lacrosse
• lacrosse ball
• lacrosse player
• Lactaid
• lactalbumin
• Lactarius
• Lactarius delicioso
• lactase
• lactase deficiency
• lactate
• lactating
• lactation
• lacteal
• lactic
• lactic acid
• lactiferous
• lactiferous duct
• lactifuge
• lacto-
• Lactobacillaceae
• lactobacillus
• Lactobacillus acidophilus