====== VERTEBRAL ARTERY ======

    * Vertebral artery 
      *  First part 
          *   Origin of artery to transverse process of 6 th cervical vertebra 
          *  Course 
          *  Runs upwards 
          *  Scalenovertebral triangle 
          *   Present at root of neck 
        *  Boundaries 
          * Lateral Scalenus anterior 
          * Medial : oblique part of  longus colli muscle 
          * Apex : transverse process of cervical vertebra 
          * Base : first part of subclavian artery 
          * Posterior wall : transverse process of C7 , ventral ramus of C8 nerve , neck of first rib 
        * Relations 
          *  Anterior 
            * Carotid sheath with common carotid artery 
            * Vertebral vein 
            * Inferior thyroid artery 
            * Thoracic duct on left side 
          * Posterior 
            * Transverse process of 7 th cervical vertebra 
            * Stellate ganglion 
            * Ventral Rami of nerves C7 , C8 
      * Second part 
        * Runs through foramina transversria of upper 6 cervical vertebra 
        * Finally reaches foramen of atlas 
        * Relations 
          * accompanied by venous plexus and a large branch from stellate ganglion
          * Ventral Rami of second to 6 th cervical nerves 
      * Third part 
        *  Lies in suboccipital triangle 
        * Emerges from atlas 
        * Winds medially around posterior aspect of arch of atlas 
        * Relations 
          *  Medial : ventral ramus of first cervical nerve
          * Lateral : rectus capitis Lateralis 
          * Posterior : semispinalis capitis 
          * Anterior : lateral mass of atlas 
      * Fourth part 
        * Atlantooccipital membrane to pons 
        * Vertebral canal it pierces duramater 
        * At lower border of pons it joins to form basilar artery 
    * Branches
      *  Cervical branches 
        *   Arise from 4 th part 
        *   Anterior spinal artery 
        * Posterior spinal artery 
        * Posterior inferior cerebellar artery 
      * Meningeal branches