NEET PG Medical – 2018 – Question – 1

Correct Answer – C
Answer -C. Neural crest
Branchial or pharyngeal arches are masses of mesoderm covered by ectoderm and lined by endoderm. Within these masses, muscular and skeletal components develop, as well as aortic arches and nerve networks. The arches are separated by grooves, visible on the surface of the embryo as pharyngeal clefts and in the interior as the pharyngeal pouches
In the human embryo, the arches are first seen during the 4th week of development.
They appear as a series of outpouchings of mesoderm on both sides of developing pharynx.
The neural crest are bilaterally paired strips of cells arising in the ectoderm at the margins of the neural tube. These cells migrate to many different locations and differentiate into many cell types within the embryo.
Neural Crest Derivatives
A key feature of neural crest is the migration into other embryonic tissues to form specific neural and non-neural populations and structures.
Cranial neural crest migration – dorsolaterally and into pharyngeal archescraniofacial mesenchyme – cartilage, bone, cranial neurons, glia, and connective tissues of the face pharyngeal arches and pouches – thymic cells, tooth odontoblasts, middle ear bones (ossicles), stria vascularis cells, and jaw (mandible)
In the body region, neural crest cells also contribute the peripheral nervous system (both neurons and glia) consisting of sensory
ganglia (dorsal root ganglia), sympathetic and parasympathetic ganglia and neural plexuses within specific tissues/organs.
In the head region, neural crest cells migrate into the pharyngeal arches forming ectomesenchyme contributing tissues which in the body region are typically derived from mesoderm (cartilage, bone,and connective tissue).