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Posterior triangle


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Posterior triangle

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