Definition is a rhetorical mode that can be used in something smaller or shorter than a full paper. You can use extended definition for several paragraphs only in a paper of much greater length. You also can add to a paper a one-paragraph definition--like a brief encyclopedia definition.
Depending upon location, neural crest cells give rise to most of the peripheral nervous system, as well as various non-neural tissues, like craniofacial bone and cartilage, the thymus and parathyroid glands, and the cardiac outflow tract â in short, all of the tissues that are affected in DiGeorge syndrome.
Elizabeth TePas, MD, MS. DiGeorge syndrome (DGS) is a constellation of signs and symptoms associated with defective development of the pharyngeal pouch system. Most cases are caused by a heterozygous chromosomal deletion at 22q11.2. The classic triad of features of DGS on presentation is conotruncal cardiac anomalies, hypoplastic thymus, and hypocalcemia (resulting from parathyroid hypoplasia). Thymic hypoplasia in DGS results in a range of T cell deficits.