Vertebrate development

• notochord is from chordamesoderm
• Amnion


  A thin, fluid-filled membrane that forms a fluid-filled sac around the embryo. It provides protection against mechanical shock and helps maintain a stable environment for the developing embryo
• Chorion


  A membrane that surrounds the amnion and forms the outermost layer of the embryonic membranes. In reptiles, birds, and some mammals, such as humans, the chorion is involved in gas exchange between the embryo and the surrounding environment
• Allantois


  A membrane that forms as an outgrowth of the embryonic gut. It initially serves as a storage organ for waste products produced by the developing embryo but later becomes involved in gas exchange and contributes to the formation of the umbilical cord in mammals
• Yolk sac


  A membranous sac that encloses the yolk, a nutrient-rich substance that provides nourishment to the developing embryo. In species with lecithotrophic development (relying on yolk for nutrition), such as many reptiles and some amphibians, the yolk sac plays a crucial role in providing nutrients to the developing embryo