Question

Notochord originates from
A. Mesoderm
B. Ectoderm
C. Endoderm
D. None of these

Answer 1

Hint: A notochord is the characteristic feature of all chordate animals. It is a tiff rod-like structure that runs along the body internally. It is initially ventral to the ectoderm. The ectoderm, mesoderm, and endoderm are three layers of the body in vertebrates.

Complete answer: The notochord is the key defining feature of the animal phylum Chordata. The other characteristic features of chordates are the presence of a dorsal nerve cord, post-anal tail and pharyngeal slits. The notochord is a rod-shaped longitudinal structure that extends along the length of the body of chordates internally. Among sub-groups of vertebrate chordates, the notochord becomes the spine. In aquatic chordates, the notochord helps the organism to swim by acting as a flexible tail structure.

The body of a chordate is made up of three distinct layers each giving rise to different organs of the body. These layers are arranged dorsal to ventral as ectoderm, mesoderm, and endoderm respectively. Thus, the ectoderm forms the external layer, the mesoderm forms the middle layer and the endodermis is the innermost layer. The notochord develops ventral to ectoderm and this means it originates from mesoderm. First, it lies below the ectoderm then below the neural plate, and finally under the neural tube. The notochord's form is three weeks in humans and contributes to the formation of the vertebral column. It starts developing from the middle of the embryo and then extends towards both caudal and cranial directions. Deformation of the notochord in human embryo development may lead to many birth defects.
Hence, the correct answer is option A.

Note: The embryonic patterning in humans is majorly influenced by notochord development. The notochord is formed by material similar to cartilage. The main function of the notochord is to act as midline tissue that provides directional signals to growing tissues in its surrounding. Various growth factors are released by notochord that assists in embryonic development.