Learning Modules - Medical Gross Anatomy
Spinal Cord and Spinal Nerve - Page 6 of 14

    
Another important feature of the spinal cord, which relates directly to its function, is its external shape. The spinal cord is shaped something like a glass soda-bottle. It has a cervical enlargement which begins at roughly C4 and extends to roughly T1 and a lumbar enlargement that extends from roughly the T11 vertebra through the L1 vertebral level. The cervical enlargement is the site of the cell bodies of the motor neurons that innervate the upper limbs, as well as the site where the sensory nerves from the upper limbs synapse. The lumbar enlargement is the site of the cell bodies of the motor neurons that innervate the lower limbs and the site where the sensory nerves from the lower limbs synapse. These segments of spinal cord are enlarged because of the extensive sensory input from the limbs, especially from the hands and fingers, as well as the complex and fine musculature of the limbs which requires significantly more innervation to control.

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