GENERAL HISTOLOGY

Detailed explanation-1: -The ectoderm is also sub-specialized to form the (2) neural ectoderm, which gives rise to the neural tube and neural crest, which subsequently give rise to the brain, spinal cord, and peripheral nerves. The endoderm gives rise to the lining of the gastrointestinal and respiratory systems.

Detailed explanation-2: -The nervous system develops from the ectoderm following an inductive signal from the mesoderm. The initial mesodermal cells condense to form the notochord, which elongates under the primitive streak along the anterior-posterior axis of the developing embryo.

Detailed explanation-3: -It is the outermost layer, and is superficial to the mesoderm (the middle layer) and endoderm (the innermost layer). It emerges and originates from the outer layer of germ cells. The word ectoderm comes from the Greek ektos meaning “outside", and derma meaning “skin". Organs derived from ectoderm.

Detailed explanation-4: -The ectoderm gives rise to the skin and the nervous system. The mesoderm specifies the development of several cell types such as bone, muscle, and connective tissue. Cells in the endoderm layer become the linings of the digestive and respiratory system, and form organs such as the liver and pancreas.

Detailed explanation-5: -Although derived from the ectoderm, the neural crest has sometimes been called the fourth germ layer because of its importance. It has even been said, perhaps hyperbolically, that “the only interesting thing about vertebrates is the neural crest” (quoted in Thorogood 1989).