Sternocleidomastoid

• Sternal head

  • Tendinous
  • Arises from superolateral part of front of manubrium sterni, below suprasternal notch
  • Passes upwards, backwards, and laterally in front of sternoclavicular joint
• Clavicular head

  • Flat and musculoaponeurotic
  • Arises from medial third of superior surface of clavicle
  • Passes vertically upwards deep to sternal head and unites with it to form a fusiform belly
• Insertion

  • Thick tendon on lateral surface of mastoid process from tip to base
  • Thin aponeurosis into lateral half of superior nuchal line of occipital bone
• Arterial supply

  • Upper part by occipital and posterior auricular arteries
  • Middle part by superior thyroid artery
  • Lower part by suprascapular artery
• Nerve supply

  Supplied by spinal accessory nerve and ventral rami of C2 and
• When muscle contracts

  1. Tilts head towards same side shoulder

  2. Rotates head so chin turns to opposite side
• When muscles of both sides contract

  Draw head forwards as in lifting head from pillow or bending head during eating
• If head is fixed by prevertebral muscles, the two sternocleidomastoid muscles act as accessory muscles of respiration during forced inspiration
• Superficial relations

  • Skin
  • Platysma
  • 3 cutaneous nerves (great auricular, transverse cervical, medial supraclavicular, lesser occipital)
  • External jugular vein
  • Superficial cervical lymph nodes
  • Parotid gland
• Deep relations - upper part


  • Muscles: Posterior belly of digastric, longissimus capitis, splenius capitis
  • Artery: Occipital artery
• Deep relations - middle part


  • Muscles: Levator scapulae, scalenus anterior, scalenus medius, scalenus posterior, splenius capitis, inferior belly of omohyoid
  • Arteries: Common carotid, internal carotid
  • Veins: Internal jugular, anterior jugular
  • Nerves: Vagus, spinal accessory, cervical plexus, brachial plexus (upper part), ansa cervicalis (inferior root)
  • Glands: Thyroid gland, lymph nodes
• Deep relations - lower part


  • Muscles: Sternohyoid, sternothyroid, scalenus anterior
  • Arteries: Suprascapular, transverse cervical
  • Veins: Anterior jugular
  • Nerves: Brachial plexus (lower part), phrenic nerve