Question

Which one develops from ectoderm?
A. Liver and heart
B. Notochord and vertebral column
C. Spinal cord and brain
D. Eye and skin

Answer 1

The body of vertebrates is made up of three layers. These are arranged in successive order as follows. The endoderm is the innermost layer, mesoderm is the middle layer, and ectoderm is the outermost layer. These layers form specific organs of the body based on the cells they contain.

Complete answer: Post fertilization, the zygote is formed that develops into three embryonic layers, which later form all the organs of the baby. The outermost layer is called the ectoderm, which is the first to form. The outer germ cells of the embryo make the ectoderm and it is found in the very early embryo. Mesoderm and endoderm are later to develop. The mesoderm is the middle layer of the body of the embryo and the endoderm is the innermost layer. The endoderm forms the innermost organs of the baby like the stomach, intestines, colon, lungs, liver and pancreas. The mesoderm forms the heart, gonads, kidneys, cartilage, muscles, blood cells, genital ducts and other organs of the baby. The outermost layer which is ectoderm forms the epithelium (skin), spinal cord, brain, nerves, ears, hair, and nails. The early embryo consists of four parts of the ectoderm. They are the external ectoderm which forms the surface of the skin, the neural plate and the neural crest which together form the neuroectoderm. The last part is the neurogenic placodes. The neuroectoderm and the neurogenic placodes receive certain cell signals from underlying mesodermal cells which initiate brain and spinal cord development.
Hence, the correct answer is option C.

Note: The 5 days old embryo is called the blastula which contains an outer layer called trophoblast and an inner layer of 150 to 200 cells called embryoblast. It is the embryoblast that initiates the division into three embryonic layers. The embryoblast layer is called the animal hemisphere. The trophoblast forms the placenta.