Neck anatomy

Cervical Fascia (Deep)

The deep cervical fascia consists of 3 layers:

  • Investing layer of deep cervical fascia
    • This is the most superficial (of deep fascia) and surrounds the entire neck
    • It splits at points to surround the trapezius muscle and sternoclydomastoid muscle; the submandibular and parotid glands
    • It attaches superiorly to the occiput (sup nuchal line); mastoid process; zygomatic arches; inferior border of mandible; hyoid bone and spinous processes of cervical vertebrae.
    • It attaches inferiorly to the clavicles; acromion and spine of scapulae and the manubrium
      • NB It attaches to the manubrium still split (from ensheathing the SCM- one anteriorly and one posteriorly)- creating a suprasternal space in which lies the anterior jugular veins
  • Pretracheal layer of deep cervical fascia
    • Surrounds the thyroid, trachea and oesophagus
  • Prevertebral layer of deep cervical fascia
    • Surrounds the vertebral column and the muscles associated with it e.g. scalenes and deep cervical muscles.
  • The carotid sheathe surrounds the carotid neurovascular bundle (Common and internal carotids; internal jugular; vagus nerve; some deep cervical lymph nodes; carotid sinus nerve and sympathetic nerve fibres)
    • It blends with the investing layer anteriorly; the pretracheal layer anterolaterally and the prevertebral layer posteriorly

Sternoclydomastoid and Trapezius (superficial muscles)

 

The Prevertebral muscles (deep muscles)

  • The pre-vertebral muscles, deep to the prevertebral fascia, are divided by:
    • neurovascular plane of the cervical & brachial plexuses and subclavian artery
  • The main muscles concerned are the
    • scalenus anterior (anterior vertebral group- in front of the plexuses)
    • scalenus medius and posterior (lateral vertebral group- behind the plexuses)
    • the levator scapulae muscle lies behind the scalenus posterior

Phrenic Nerve (C3, 4, 5)

  • Formed at the lateral borders of the scalenus anteriors and run anterior to it, then deep to the IJVs and SCMs, pass under the prevertebral fascia between subclavian arteries and veins and proceed into the thorax
  • motor supply to the muscle of the diaphragm as well as sensation to much of the diaphragm, the overlying pleura and underlying peritoneum (referred pain). The phrenic also gives sensory supply to the pericardium.

The Jugulars

  • The external jugular
    • begins just behind the angle of the mandible with the union of the retromandibular and posterior auricular veins
    • It passes towards the clavicle and, in doing so, crosses the SCM obliquely.  Once at the base of the neck, it pierces the investing fascia to enter the anteroinferior part of the lateral cervical region.
      • NB because of this ‘piercing’- in any injury above here, the wall of the EJV will be held open and air can be sucked into the vein (air embolus- can be fatal)
  • The internal jugular
    • drains blood from the brain, anterior face, cervical viscera and deep muscles of the neck
    • lies in a line from just below the external acoustic meatus, towards the medial end of the clavicle, deep and between the heads of the SCM.

Lymph nodes

  • Superficial
      • Submental (under the point of the chin)
      • Submandibular (alongside the submandibular gland)
      • Retromandibular or parotid (in the substance of the parotid gland)
      • Retro-auricular or mastoid (over the mastoid process)
      • Occipital (at the superior nuchal line, medially; enlarged in rubella)
    • Head and neck structures either drain to the superficial nodes and then to deep nodes or may drain directly to deep nodes
  • Deep
    • Scattered along the length of the internal jugular vein
    • Inferiorly they drain to the jugular lymph trunk and then to the junction of the internal jugular and subclavian veins. On the left, this is via the thoracic duct.
      • Jugulodigastric nodes are palpable anterior to sternocleidomastoid at the level of the angle of the mandible, usually as a result of nasal, pharyngeal (tonsillar) and ear infections
      • Jugulo-omohyoid nodes are palpable posterior to the lower one-third of sternocleidomastoid

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