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L05 and L06 - Superficial Back Muscles and Posterior Shoulder with Deep Back Muscles and Suboccipital Triangle Thursday, October 30, 2014 11:00 AM Types of back muscles: – Superficial muscles: extrinsic and move the appendicular muscles Hypaxial differentiation Innervated by ventral motor roots which split into ventral rami – Deep muscles: intrinsic and move the head and the trunk, acting on the spine as principle extensors in lateral flexion and rotation spanning from the pelvis to the skull base Epaxial differentiation Innervated by dorsal sensory root which split into dorsal rami – Movements rarely involve a single muscle, acting in coordinated and synergistic movements Superficial back muscles and associated structures: – Trapezius Scapular movements: ► Elevation and depression ► Superior and inferior rotation ► Protraction and retraction – Latissimus Dorsi: possesses fibers that attach to the scapula as it crosses the inferior angle of the scapula Innervation: thoracodosal nerve -- a branch of the posterior cord of the brachial plexus made of cranial nerve VI, VII, and VIII – Triangle of Auscultation -- created by the superior latissimus dorsi, medial border of the scapula, lateral trapezius – Levator Scapulae – Rhomboid Major – Rhomboid Minor Intermediate back muscles and associated structures: – Serratus Posterior Superior – Serratus Posterior Inferior Posterior shoulder muscles and associated structures: – Teres Major – Deltoid – Bursae -- flat sac of synovial membrane that lubricates the joint Shoulder: Subacromial Head and Subdeltoid Head Anatomy Page 1 Clinical causes of bursitis: ► Calcifying tendinitis -- calcification of the tendon and related degenerative change ► Supraspinatous tendon avulsion -- rotator cuff tear □ Rotator Cuff -- musculotendinous cuff of 4 muscles that adhere to the fibrous capsule of the glenohumerol joint, stabilizing the joint (as the only muscle that inserts on the greater and lesser tubercles of the humerus) Supraspinatus Infraspinatus Teres Minor Subscapularis – Serratus Anterior Innervation: long thoracic nerve that runs along the surface of the muscle – Anatomical spaces formed by muscles near the proximal arm containing neurovasculature: Quadrangular space -- bound by the teres minor, teres major, surgical neck of the humerus, and long head of the triceps ► Contains: posterior circumflex humeral artery, axillary nerve Triangular space -- bound by the teres minor, teres major, and long head of the triceps ► Contains: circumflex scapular artery Other associations: – Cutaneous nerve supply: Posterior cutaneous nerves as medial branches of the dorsal rami and lateral branches of the dorsal rami Lateral cutaneous nerves as posterior branches of the ventral rami – Blood supply: Subclavian artery of the thyrocervical trunk ► Superficial transverse cervical artery ► Deep dorsal scapular artery ► Suprascapular artery Rib 1 Axillary artery Anatomy Page 2 ► Deep dorsal scapular artery ► Suprascapular artery Rib 1 Axillary artery ► Subscapular artery □ Thoracodorsal nerve □ Circumflex scapular artery ► Posterior humeral circumflex artery Scapular anastomosis -- a system connecting certain subclavian artery and their corresponding axillary artery, forming a circulatory anastomosis around the scapular (that allows blood to flow past the joint in the event of occlusion, damage, or pinching of the transverse cervical artery, dorsal scapular artery, suprascapular artery, branches of the subscapular artery, and branches of the thoracic aorta) Deep back muscles: – Thoracolumbar fascia -- dense, tough connective tissue layers, extending from the iliac crest and dorsal sacrum upwards to the thoracic region and neck Tri-laminar (as posterior, middle, and anterior portions) in the lumbar region Functions: invests the intrinsic back muscles in a fascial compartment, serves as attachment points for several muscles (e.g., latissimus dorsi, internal oblique, transversus abdominis), continues into the neck as nuchal fascia – Superficial: Splenius – Intermediate: organized into groups based on attachment and function that are deep to the extrinsic Anatomy Page 3 – Intermediate: organized into groups based on attachment and function that are deep to the extrinsic muscles, innervating from the dorsal (posterior) rami of the spinal nerves with vasculature supply from the posterior branches of the aorta Erector Spinae ("I like spaghetti"): ► Lateral: Iliocostalis ► Less lateral/more medial: longissimus ► Medial: Spinalis □ Spinalis cervicis □ Spinalis thoracis – Deep: Transversospinales -- relatively short muscles that attach to the transverse processes inferiorly and the spinous processes superiorly (in the groove), innervating with the dorsal (posterior) rami with vasculature supply from the posterior branches of the aorta Superficial: Semispinalis ► Semispinalis capitis Less superficial/more deep: Multifidus (prominent in the lumbar region) Deep: Rotatores (prominent in the thoracic region) -- densely loaded with sensory organs, acting as proprioceptive organs Minor muscles: ► Levator costarum □ Innervation: dorsal (posterior) rami ► Intertransversarii □ Innervation: dorsal (posterior) rami (except the anterior cervical intertransversarii) ► Interspinales □ Innervation: dorsal (posterior) rami Suboccipital triangle -- located at the posterior base of the skull (deep to the trapezius, sternocleidomastoid, splenius, and semispinalis muscles), acting principally as postural muscles that assist in stabilizing the upper cervical spine and skull – Includes: C1-C2, 2 small muscle pairs, multiple nerves, and the vertebral artery Rectus Capitis Posterior on the superiomedial border of the triangle ► Major ► Minor Obliquus Capitis on the superlateral and inferior borders of the triangle ► Superior ► Inferior – Landmarks: External occipital protuberance Anatomy Page 4 ► Superior ► Inferior – Landmarks: External occipital protuberance C2 spinous process Inerfior nuchal line Foramen magnum Transverse foramina of C1-C2 – Innervation: Suboccipital nerve -- dorsal rami of C1 spinal nerve that acts primarily in motion to the muscles of the triangle Greater occipital nerve -- dorsal rami of C2 spinal nerve that acts primarily in sensory to the suboccipital region and posterior scalp, emerging inferior to the obliquus capitis inferior Vasculature: vertebral artery -- arises from the subclavian artery in the root of the neck, passing through the transverse foramina of all the cervical vertebra (except C 7) before coming together to form the basilar artery at the foramen magnum Anatomy Page 5