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Posterior triangle

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  • 1. Posterior Triangle of the Neck Maribel G. Castro-Enano, M.D. CPU College of Medicine
  • 2. Surface Anatomy of the Neck
    • Spinous process of the axis – first bony prominence that can be felt in the median plane
    • Spinous process of the vertebra prominens (C7) – easily palpable when the neck is flexed
    • Thyroid cartilage (Adam’s apple) – at the level of C4; contains 2 quadrilateral plates called laminae
    • Hyoid bone – u-shaped bone at the level of the body of C3; lie superior to the thyroid cartilage
    • Transverse process of the atlas – felt by deep palpation between the angle of the mandible and a point about 1cm anteroinferior to the tip of the mastoid process
  • 3. Surface Anatomy of the Neck
    • Cricoid cartilage – inferior to the thyroid cartilage; lies at the level of C6
    • Tracheal rings – palpable in the inferior part of the neck; moves superiorly during swallowing
    • Jugular notch – depression in the manubrium of the sternum; easily palpable between the medial ends of the clavicle
    • Sternocleidomastoid muscle – has sternal and clavicular heads; divides lateral side of the neck into anterior and posterior triangles
    • Supraclavicular fossa – triangular depression between the sternal and clavicular heads of the SCM; contains the pressure point for the subclavian artery
  • 4. Surface Anatomy of the Neck
    • Medial ends of the clavicle – clearly visible at the root of the neck
    • Inferior margin of the mandible , the mastoid process of the temporal bone, and the external occipital protuberance – bony landmarks of the superior limit of the neck
  • 5. Superficial Structures
    • Superficial Fascia – contains the platysma
    • Platysma – wide, thin subcutaneous sheet of striated muscle that ascends to the face from the anterior part of the neck
    • - covers the superior part of the anterior cervical triangle and the anteroinferior part of the posterior cervical triangle
    • Inferior Attachment – fascia and skin over the pectoralis major (second rib) and deltoid muscles
    • Superior Attachment – inferior border of mandible and skin of the lower face
    • Innervation – cervical branch of CN VII
    • Action – muscle of facial exrpression; tense the subcutaneous tissue of the neck and assist in depressing the lower lip
    • - produces skin ridges in the neck, releasing pressure of the skin on the the underlying veins
  • 6. Superficial Structures
    • 1. Superficial or Enveloping Layer
    • - surrounds the whole neck
    • - starts off at the back where it is attached to the ligamentum nuchae
    • - encloses the trapezius and SCM muscles
    • - contains the accessory nerve as it passes posteriorly and inferiorly from the SCM to the trapezius
  • 7. Superficial Structures
    • 2. Prevertebral Fascia
    • - part of the fascia that envelopes the vertebral column
    • - envelopes the prevertebral and postvertebral muscles of the neck
    • - covers the subclavian vessels and the roots of the brachial plexus
    • - drawn into the axilla on the brachial plexus and subclavian artery as the axillary sheath
    • * provides an anatomical course for infections within the posterior compartment of the neck to travel into the axilla
  • 8. Superficial Structures
    • 3. Carotid Sheath
    • - anterior to the prevertebral fascia
    • - invests the common and internal carotid arteries, the internal jugular vein and the vagus nerve
  • 9. Superficial Structures
    • 5. Infrahyoid Fascia
    • - encloses the infrahyoid muscles ( sternothyroid, sternohyoid, thyrohoid and cricohyoid m.)
    • - attaches above either into the hyoid or thyroid muscles and below into the posterior aspect of the manubrium
  • 10. Fascial Layers
  • 11. Superficial Structures
    • 4. Pretracheal Fascia
    • - has 2 layers, the anterior and posterior layers
    • a. anterior layer – superiorly attached to the hyoid bone up to the border of the mandible
    • - inferiorly found anterior to the larynx, trachea and thyroid gland and end in front of the great vessels
    • b. posterior layer – posterior to the pharynx and esophagus
    • - covers the posterior aspect of the esophagus
    • - the anterior and posterior layers are both attached the the skull
  • 12. Posterior Triangle of the Neck
    • A. Boundaries
    • - bounded by the middle one-third of the clavicle, SCM muscle and the trapezius muscle
    • - roof : investing fascia
    • - floor: levator scapulae – middle position
    • splenius – superior to levator scapulae
    • scalenes – inferior to levator scapulae
    • semispinalis capitis – may appear at the apex of the post. triangle
  • 13.  
  • 14. Posterior Triangle of the Neck
    • ACTION:
    • SCM Muscle
    • - flex the head when they contract bilaterally
    • - individually, rotates the head toward the opposite side of the body
    • - accessory muscle of respiration
    • Trapezius Muscle
    • - elevates the shoulder girdle and helps to support the weight of the upper limb
    • - lower fibers draw the scapula toward the vertebral column
  • 15. Posterior Triangle of the Neck
    • A. Boundaries con’t…
    • - the apex of the triangle projects superiorly behind the ear to the level of the superior nuchal line of the occipital bone, where the SCM and trapezius muscles meet
  • 16. Posterior Triangle of the Neck
    • SCM and Trapezius Muscles
    • - have a continuous superior attachment from the mastoid process to the inion along the superior nuchal line
    • - inferior attachments
    • SCM – medial third of clavicle and sternum
    • trapezius – lateral third of clavicle, acromion and spine of the scapula
    • - innervated by CN XI
  • 17. Posterior Triangle of the Neck
    • Contents of the Posterior Triangle
    • 1. Accessory Nerve – divides the fascial roof into a superior portion ( carefree part ) and a lower portion which contains the cutaneous branches of the cervical plexus
    • 2. Cutaneous Cervical Nerves
      • - innervate the skin of the neck and shoulder region
      • - derived from the anterior rami of cervical nerves 2, 3 and 4
  • 18. Posterior Triangle of the Neck
    • Cutaneous Cervical Nerves
    • a. lesser occipital nerve – supplies the skin posterior to the ear and superficial to the mastoid process
    • b. greater auricular nerve – supplies the skin overlying the upper aspect of the SCM, the earlobe and the parotid gland
    • c. transverse cervical nerve – innervates skin of the neck overlying the laryngeal prominence
    • d. supraclavicular nerves – innervate the skin that is superficial to the clavicle and scapula
  • 19. Posterior Triangle of the Neck
    • Contents of the Posterior Triangle con’t…
    • 3. Omohyoid M. – a digastric muscle ( 2 bellies)
    • - inferior belly passes through the lower aspect of the posterior triangle as it inserts into the upper margin of the scapula
    • - superior belly in the anterior triangle
    • - intervening tendon bound to the clavicle by a fascial sling
    • 4. External Jugular Vein – descends subcutaneously across the SCM and pierces the fascia that forms the roof of the post. triangle
    • - terminates in the subclavian or internal jugular vein at the base of the posterior triangle
  • 20. Posterior Triangle of the Neck
    • Contents of the Posterior Triangle con’t…
    • 5. Subclavian Vein – continuation of the axillary vein
    • - begins at the lateral border of the first rib and ends medial to the scalenus anterior m. where it joins the internal jugular vein to form the braciocephalic vein
    • 6. Subclavian Artery – enters the post. triangle posterior to the insertion of scalenus anterior ( arises from the anterior tubercle of the transverse processes of the cervical vertebrae C3-6, inserts into the scalene tubercle of the 1 st rib and separates the subclavian artery and vein at its insertion)
  • 21. Posterior Triangle of the Neck
    • - subclavian artery in the post. triangle may give off a dorsal scapular artery which traverses through the trunks of the brachial plexus to supply the medial border of the scapula and the rhomboids
    • * Important Relationships Around the Subclavian A.
    • 1. Inferiorly – 1st rib and pleura of apex of lung
    • 2. Posteriorly – scalenus medius and lower trunk of brachial plexus
    • 3. Anteriorly – scalenus anterior
  • 22. Posterior Triangle of the Neck
    • 7. Suprascapular Artery – arise from the first part of the subclavian a.
    • - supply the supraspinatus and infraspinatus fossae structures of the scapula
    • 8. Transverse Cervical Artery – arise from the first part of the subclavian a.
    • - innervate the posterior surface of the trapezius through a superficial branch; deep branches supply the rhomboids and medial border of the scapula
  • 23. Posterior Triangle of the Neck
    • 9. Lateral group of the inferior deep cervical lymph nodes
    • - on the posterior margin of the SCM at the level of CN XI
    • - drain the back of the scalp and neck and drain into the jugular lymphatic trunks
    • 10. Brachial Plexus – formed by the ventral rami of C5,6,7,8 and T1 (C4 and T2)
  • 24.  
  • 25. Posterior Triangle of the Neck
    • THE BRACHIAL PLEXUS
    • 1. upper trunk – C5 and C6 anterior and
    • 2. middle trunk – C7 posterior divisions
    • 3. lower trunk – C8 and T1
    • * posterior cord – 3 posterior divisions
    • * lateral cord – anterior divisions of the upper and middle trunks
    • * medial cord – anterior division of the lower trunk
  • 26. The Brachial Plexus
  • 27. Posterior Triangle of the Neck
    • THE BRACHIAL PLEXUS cont……
    • * suprascapular nerve – major nerve that arises from the upper trunk of the brachial plexus (C5,6); passes through the suprascapular notch to innervate and supraspinatus and infraspinatus m.
    • *Branches from the roots of the brachial plexus innervate the following:
    • Rhomboids – dorsal scapular nerve, C5
    • Serratus anterior – long thoracic n., C5,6,7
    • Diaphragm - phrenic n., C3,4,5
    • Adjacent prevertebral muscles
    • * subclavius muscle – branch from the upper trunk of the brachial plexus in the posterior triangle
  • 28. Good Afternoon!