Question

Which of the following organs develop first?

• A. Liver
• B. Heart
• C. Kidneys
• D. Notochord

Answer 1

The correct option is D Notochord

• The notochord is a flexible rod-like structure of mesodermal cells that is the principal longitudinal structural element of chordates and of the early embryo of vertebrates, in both of which it plays an organizational role in nervous system development.
• In later vertebrate development, it becomes part of the vertebral column.
• The notochord derived during gastrulation (infolding of the blastula, or early embryo) from cells that migrate anteriorly in the midline between the hypoblast and the epiblast (inner and outer layers of the blastula).
• These cells coalesce immediately beneath the developing central nervous system.
  

So the correct option is 'notochord'.