Question

Notochord develops from

• A. Primary ectoderm
• B. Primary endoderm
• C. Primary mesoderm
• D. Both A and B

Answer 1

The correct option is C Primary mesoderm

The inner cell mass of the blastocyst after implantation differentiates into an outer ectoderm, middle mesoderm and inner endoderm. These layers then develop into tissues and organs of the embryo. Endoderm gives rise to certain organs including the colon, stomach, intestines, liver, lungs and pancreas. Mesoderm gives rise to heart, kidneys, gonads, genital ducts, cartilage, bones, muscles, blood cells, and other structures. Ectoderm forms the outer linings like the epithelium, brain, spinal cord, nerves, ears, nails and hair. So the notochord which later forms the spine develops from the mesoderm.

So the correct answer is C.