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