SCALENE

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SCALENE PREVERTEBRAL MUSCLES CERVICAL PLEXUS

• Dr. Mujahid Khan

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Scalenus Anterior Muscle

• The scalenus anterior muscle is a key muscle in
  understanding the root of the neck
• It is deeply placed
• It descends almost vertically from the vertebral
  column to the first rib

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Anterior Relation

• Related to the carotid arteries, the vagus nerve,
  the internal jugular vein, and the deep cervical
  lymph nodes
• The transverse cervical and suprascapular
  arteries and the prevertebral layer of deep
  cervical fascia bind the phrenic nerve to the
  muscle

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Posterior Relation

• Related to the pleura, the origin of the brachial
  plexus, and the second part of the subclavian
  artery
• The scalenus medius muscle lies behind the
  scalenus anterior muscle

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Medially

• Related to the vertebral artery and vein and the
  sympathetic trunk
• On the left side, the medial border is related to
  the thoracic duct

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Laterally

• Related to the emerging branches of the cervical
  plexus, the roots of the brachial plexus, and the
  third part of the subclavian artery

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Scalenus Anterior Muscle

• Origin
• Transverse processes of third, fourth, fifth, and
  sixth cervical vertebrae
• Insertion
• First rib
• Action
• Elevates first rib, laterally flexes and rotates
  cervical part of vertebral column

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Scalenus Medius

• It lies behind the scalenus anterior
• It extends from the transverse process of the
  atlas and the transverse processes of the next
  five cervical vertebrae
• Inserted into the upper surface of the first rib
  behind the groove for the subclavian artery
• The muscle lies behind the roots of the brachial
  plexus and the subclavian artery

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Scalenus Posterior

• Origin
• Transverse processes of lower cervical vertebrae
• Insertion
• Second rib
• Action
• Elevates second rib, laterally flexes and rotates
  cervical part of vertebral column

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Longus Colli Muscle

• Origin
• Anterior tubercle of C1, bodies of C1 to C3 and
  transverse processes of C3 to C6 vertebrae
• Insertion
• Bodies of C5 to T3 vertebrae, transverse
  processes of C3 to C5 vertebrae
• Action
• Flexes neck with rotation to opposite side

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Longus Capitis Muscle

• Origin
• Basilar part of occipital bone
• Insertion
• Anterior tubercles of C3 to C6 transverse
  processes
• Action
• Flexes the head

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Rectus Capitis Anterior

• Origin
• Base of the skull, just anterior to the occipital
  condyle
• Insertion
• Anterior surface of lateral mass of atlas
• Action
• Flexes the head

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Rectus Capitis Lateralis

• Origin
• Jugular process of occipital bone
• Insertion
• Transverse process of atlas
• Action
• Flexes head and helps stabilize it

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Splenius Capitis

• Origin
• Inferior half of nuchal ligament and spinous
  processes of superior 6 thoracic vertebrae
• Insertion
• Lateral aspect of mastoid process and lateral
  third of superior nuchal line
• Action
• Laterally flexes and rotates head and neck to
  same side, extend head and neck

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Cervical Plexus

• The cervical plexus is formed by the anterior
  rami of the first four cervical nerves
• The rami are joined by connecting branches, which
  form loops that lie in front of the origins of
  the levator scapulae and the scalenus medius
  muscles

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Cervical Plexus

• The plexus is covered in front by the
  prevertebral layer of deep cervical fascia
• Is related to the internal jugular vein within
  the carotid sheath
• The cervical plexus supplies the skin and the
  muscles of the head, the neck, and the shoulders

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Cutaneous Branches

• The lesser occipital nerve (C2)
• Supplies the back of the scalp and the auricle
• The greater auricular nerve (C2 and3)
• Supplies the skin over the angle of the mandible
• The transverse cervical nerve (C2 and 3)
• Supplies the skin over the front of the neck

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Cutaneous Branches

• The supraclavicular nerves (C3 and 4)
• The medial, and intermediate, and lateral
  branches supply the skin over the shoulder region
• These nerves are important clinically, because
  pain may be referred along them from the phrenic
  nerve (gallbladder disease)

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Muscular Branches

• Prevertebral muscles, sternocleidomastoid
  (proprioceptive, C2 and 3), levator scapulae (C3
  and 4), and trapezius (proprioceptive, C3 and 4)
• A branch from C1 joins the hypoglossal nerve
• Some of these C1 fibers later leave the
  hypoglossal as the descending branch, which
  unites with the descending cervical nerve (C2 and
  3), to form the ansa cervicalis

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Muscular Branches

• The first, second, and third cervical nerve
  fibers within the ansa cervicalis supply the
  omohyoid, sternohyoid, and sternothyroid muscles
• Other C1 fibers within the hypoglossal nerve
  leave it as the nerve to the thyrohyoid and
  geniohyoid

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Phrenic Nerve

• It arises in the neck from the third, fourth, and
  fifth cervical nerves of the cervical plexus
• It runs vertically downward across the front of
  the scalenus anterior muscle
• Enters the thorax by passing in front of the
  subclavian artery

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Phrenic Nerve

• The phrenic nerve is the only motor nerve supply
  to the diaphragm
• It also sends sensory branches to the
  pericardium, the mediastinal parietal pleura, and
  the pleura and peritoneum covering the upper and
  lower surfaces of the central part of the
  diaphragm