In adult spinal cord normally ends at ?

Ans. is 'a' i.e., Lower border of LI The spinal cord is an elongated cylidrical lower pa of CNS occupying upper two thirds of veebral canal.It is enveloped by three meningeal layers - dura, arachnoid and pia maters.Spinal cord gives origin to 31 pairs of spinal nerves (8 cervical , 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal). The spinal cord begins as a continuation of medulla oblongata at the level of upper border of atlas (C1 veebra) andends at lower border of Ll in adults.In newborn its termination is at L3 level.Spinal cord is as long as veebral canal till 3rd month of intrauterine life and therefore veebral column grows more rapidly so that at bih the level of termination lies at L3 level.Inferiorly spinal cord terminates as conus medullaris.It is 18 inches (45 cm) long in adult male and 42 cm long in adult female.It is not uniformly cylindrical but shows two enlargements : cervical (C3-T2) and lumbar. (L1-S3).