The spinal crd is the lower elongated, cylindrical part of the CNS. It occupies the upper 2/3 of the vertebral canal. It extends ffrom the level of the upper border of the atlas to the lower border of L1 or upper of L2. It is about 45sm long. The loer end is conus medullaris, a terminal filum terminal. It has 2 thickenings-cervical and lumbar enlargments which give large nerves for the limbs. The spinal cord gives off 31 pairs of spinal nerves. Internal structure-Transverse section od S.C.forms H shaped mass of the grey matter. In the grey matter we can see horns: ant, post, and lateral. The white matter of the spinal cord is divisible into right and left halves, in front by a deep ant.median fissure, and behind by the post med.fissure. In each white half matter is divided into the post white column, lat white column, ant.white column. Each spinal nerve arises by 2 roots: ant/ventral and dorsal/post. 1 spinal nerve constitutes one spinal segment. Tracts of spinal cord- a collection of fibers that connects 2 matters of grey matter within the CNS is called a tract: ascending and descendeing. The meninges- The brain and spinal cord are enclosed by the 3 membraneous covering or meninges. These are from outside dura mter, the pia mater, and arachnid mater.Arahnoid mater- is thin transparent membrane. It separates from dura by subdural space containing cerebrospinal fluid. Pia mater-is thin vascular membrane, dipping into various sulci and other irregularities of its space.
69. Topographical anatomy of the facial department of the Head: parotid, masseteric and buccal regions. The parotid salivary gland: structure, topography, excretory duct, blood & nerve supply, lymphatic drainage. Sublingual & submandibular salivary glands: structure, topography, excretory duct, blood & nerve supply, lymphatic drainage.