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Triangles and Root of the Neck Human Musculoskeletal System Kittikun Viwatpinyo, Ph.D. Neck : Introduction • Neck (Cervical region) ▫ Area in between base of skull to T1 vertebra, clavicle and acromion • Transitional area between head, thorax and upper limb (Drake, Wayne & Mitchell, 2005) Neck : Surface anatomy Superficial structures of neck • Skin • Superficial fascia • Platysma muscle (Tank, 2005) Superficial structures of neck • Cutaneous nerves (Tank, 2005) (Moore, Dalley & Agur, 2010) Superficial structures of neck • Superficial veins : (Moore, Dalley & Agur, 2010) Deep cervical fascia • Investing layer • Prevertebral layer • Pretracheal layer • Carotid sheath (Moore, Dalley & Agur, 2010) Fascial spaces • “Potential spaces” • Pretracheal space • Retropharyngeal space • Prevertebral space (Moore, Dalley & Agur, 2010) Fascial spaces (Drake, Wayne & Mitchell, 2005) Anterior triangle of neck • Area anterior to sternocleidomastoid muscle • Sub-triangles : ▫ ▫ ▫ ▫ Submental Submandibular Carotid Muscular (Moore, Dalley & Agur, 2010) Skeletal landmarks • Hyoid bone • Thyroid cartilage ▫ Thyroid prominence ▫ Oblique line ▫ Thyrohyoid membrane • Cricoid cartilage (Drake, Wayne & Mitchell, 2005) Muscles of anterior triangle • Suprahyoid muscles ▫ Digastric m. ▫ Stylohyoid m. ▫ Mylohyoid m. (Moore, Dalley & Agur, 2010) (Drake, Wayne & Mitchell, 2005) Muscles of anterior triangle • Infrahyoid muscles ▫ ▫ ▫ ▫ Sternohyoid m. Omohyoid m. Sternothyroid m. Thyrohyoid m. (Moore, Dalley & Agur, 2010) Nerves of anterior triangle • Vagus nerve (CN. X) ▫ Located within carotid sheath posterior to vessels ▫ Major branch : Superior laryngeal n. Internal and External laryngeal nerves (Drake, Wayne & Mitchell, 2005) Nerves of anterior triangle • Hypoglossal nerve (CN. XII) ▫ Located anterior to carotid arteries and medial to digastric and stylohyoid muscles ▫ In submandibular triangle : located lateral to hyoglossus muscle (Moore, Dalley & Agur, 2010) Nerves of anterior triangle • Transverse cervical nerve (C2, C3) ▫ Receives sensation from skin of anterior triangle (Tank, 2005) (Drake, Wayne & Mitchell, 2005) Nerves of anterior triangle • Ansa cervicalis ▫ Loop of motor branches of cervical plexus (C1-C3) ▫ Located anterior to carotid sheath ▫ Superior and inferior roots ▫ Supplies infrahyoid muscles (except thyrohyoid m.) (Tank, 2005) Carotid arterial system • Common carotid artery ▫ Bifurcates at level of upper border of thyroid cartilage • Internal carotid artery ▫ Directs into skull ▫ No branches in neck • External carotid artery ▫ Gives many branches to neck and facial structures (Moore, Dalley & Agur, 2010) External carotid artery : branches • Superior thyroid artery Superior laryngeal a. : pierces thyrohyoid membrane to supply larynx Glandular branches : supply thyroid gland (Drake, Wayne & Mitchell, 2005) External carotid artery : branches • Lingual artery ▫ Passes anteriorly and deep to hyoglossus muscle to supply tongue (Drake, Wayne & Mitchell, 2005) External carotid artery : branches • Facial artery ▫ Passes anteriorly and medial to posterior belly of digastric muscle and travels along inf border of mandible ▫ Supplies submandibular salivary gland, submental region and face (Drake, Wayne & Mitchell, 2005) External carotid artery : branches • Occipital artery ▫ Passes posteriorly and medial to posterior belly of digastric muscle ▫ Supplies sternocleidomastoid muscle and posterior part of scalp (Drake, Wayne & Mitchell, 2005) Carotid pulse (Drake, Wayne & Mitchell, 2005) Internal jugular vein • IJV : located lateral to common carotid a. • Joins subclavian vein at venous angle • Major tributaries ▫ Facial vein ▫ Lingual vein ▫ Superior and middle thyroid veins ▫ Occipital vein (Moore, Dalley & Agur, 2010) Lymphatics of the neck • Superficial lymph nodes ▫ Occipital nodes ▫ Mastoid nodes ▫ Parotid nodes ▫ Submental nodes ▫ Submandibular nodes ▫ Superficial cervical nodes (Drake, Wayne & Mitchell, 2005) Lymphatics of the neck • Deep cervical lymph nodes ▫ Superior deep cervical nodes ▫ Inferior deep cervical nodes ▫ Pretracheal and Paratrachel nodes (Moore, Dalley & Agur, 2010) Posterior triangle of neck • Area posterior to sternocleidomastoid muscle • Sub-triangles : ▫ Occipital ▫ Omoclavicular (Moore, Dalley & Agur, 2010) Muscles of posterior triangle • Sternocleidomastoid muscle (SCM) ▫ Origin : Mastoid process and lateral ½ of sup nuchal line ▫ Insertion : medial 1/3 of clavicle and upper manubrium ▫ Nerve : Spinal accessory nerve (CN. XI) (Drake, Wayne & Mitchell, 2005) Muscles of posterior triangle • Sternocleidomastoid muscle : Actions ▫ Extends neck (when in anatomical position) ▫ Flexes neck (when neck is initially flexes) ▫ Rotates neck to opposite side (unilateral) (Moore, Dalley & Agur, 2010) Muscles of posterior triangle • Scalene muscles ▫ Scalenus anterior ▫ Scalenus medius ▫ Scalenus posterior • Main action : Flex neck and elevate ribs 1-2 (Drake, Wayne & Mitchell, 2005) Nerves of posterior triangle • Accessory nerve (CN. XI) ▫ Passes downward and posteriorly to supplies SCM and Trapezius muscles ▫ Just beneath investing fascia frequently injured ▫ “Careful region of the posterior triangle” (Tank, 2005) Nerves of posterior triangle • Cervical plexus : from ventral rami of C1-C4 ▫ Muscular branches : Ansa cervicalis and Phrenic n. ▫ Cutaneous branches Nerves of posterior triangle • Supraclavicular part of brachial plexus (root + trunk level) ▫ Passes between scalenus anterior and medius muscles (Drake, Wayne & Mitchell, 2005) Nerves of posterior triangle • Terminal branches ▫ ▫ ▫ ▫ Dorsal scapular n. (C5) Long thoracic n.(C5 – C7) Suprascapular n. (C5, C6) Nerve to subclavius (C5, C6) (Drake, Wayne & Mitchell, 2005) Arteries of posterior triangle • Branches from Subclavian artery ▫ Suprascapular artery ▫ Transverse cervical artery (Drake, Wayne & Mitchell, 2005) Root of the neck • Deep part of neck that connects with thorax (via superior thoracic aperture) (Drake, Wayne & Mitchell, 2005) Root of the neck • Major contents : Subclavian vessels, Nerves, Lymph trunks, Visceral structures (Moore, Dalley & Agur, 2010) Subclavian artery • From Brachiocephalic trunk (right) and aortic arch (left) ▫ Curves laterally in between Scalenus anterior and medius muscles ▫ Continues as Axillary artery ▫ Three parts (related with scalenus anterior muscle) (Tank, 2005) Subclavian artery : branches • First part : Vertebral a., Internal thoracic a. & Thyrocervical trunk • Vertebral artery ▫ Passes upward and medial to scalenus anterior m. ▫ Penetrates foramen transversarium (mostly C6) (Drake, Wayne & Mitchell, 2005) Subclavian artery : branches • Internal thoracic artery ▫ Pass downward to supply anterior thoracic wall • Thyrocervical trunk ▫ Suprascapular a. ▫ Transverse cervical a. gives superficial and deep branches ▫ Inferior thyroid a. (Moore, Dalley & Agur, 2010) Subclavian artery : branches • Second part : Costocervical trunk ▫ Give rises to Deep cervical artery and Superior thoracic artery Subclavian artery : branches • Third part : ▫ In 1/3 give rises to Dorsal scapular artery (replace deep branch of transverse cervical artery) Subclavian vein • Subclavian vein ▫ Continues from Axillary vein ▫ Passes anterior to scalenus anterior muscle and join IJV at venous angle ▫ Drained into Brachiocephalic vein (Drake, Wayne & Mitchell, 2005) Lymph trunks and nodes • At venous angle, lymph trunks join venous system: ▫ Left side : Thoracic duct ▫ Right side : Rt lymphatic duct • Supraclavicular lymph nodes can be found along subclavian vein (Moore, Dalley & Agur, 2010) Nerves of root of the neck • Vagus nerve ▫ Recurrent laryngeal nerve : passes in tracheo-esophageal groove to supply internal laryngeal muscles (Drake, Wayne & Mitchell, 2005) Nerves of root of the neck • Phrenic nerve (C3-C5) ▫ Passes anterior to scalenus anterior muscle and descends into thorax to supplies diaphragm (Drake, Wayne & Mitchell, 2005) Nerves of root of the neck • Cervical part of sympathetic trunk ▫ A bundle of sympathetic fibers posterior to carotid sheath ▫ Three ganglions (location of postganglionic sympathetic neurons) • Lesion : Horner’s syndrome ▫ loss of sympathetic control in head (Drake, Wayne & Mitchell, 2005) Nerves of root of the neck • Cervical sympathetic ganglions ▫ Superior cervical ganglion : sends symp fibers into head and neck along internal carotid artery ▫ Middle & Inferior cervical ganglions sends symp fibers to heart (Drake, Wayne & Mitchell, 2005)