2b PT 500 Back Muscles.pdf

1 PT 500 Human Anatomy Muscles of the Trunk 1. Overview: Trunk muscles can be described by their function and their layering...

1 PT 500 Human Anatomy Muscles of the Trunk 1. Overview: Trunk muscles can be described by their function and their layering a. Intrinsic Muscles: act primarily on the spine (usually deeper) b. Extrinsic Muscles: act on the upper limb or as respiratory muscles (more superficial) 2. Posterior Extrinsic Muscles a. Superficial Posterior Extrinsics (Shoulder Girdle): vertebral column to upper extremity (do not focus on these now. They will come with the shoulder) i. Trapezius ii. Lattisimus dorsi iii. Rhomboids (major and minor) iv. Levator scapula Section 1  2 b. Intermediate Extrinsics (posterior respiratory muscles): vertebral column to ribs (don’t memorize the attachments, just know general location) i. Serratus posterior superior ii. Serratus posterior inferior Muscle Origin Insertion Action Innervation Serratus Post Nuchal Ligament Superior border Proprioceptive 2nd-5th Superior SP C7-T3 ribs 2-4 May elevate ribs intercostal nn Serratus Post Inferior border R Proprioceptive: SP T11-L2 APRs T9-T12 Inferior 8-12 near angle May depress ribs Section 1  3 3. Superficial Anterior Extrinsics: Thoracic cage to upper extremity (details will come with upper extremity) a. Pectoralis major b. Pectoralis minor c. Serratus anterior How can these muscles act on the trunk versus the upper extremity? What role can these muscle play in respiration? Section 1  4 4. Muscles of the Thoracic Cage a. Intercostal Muscles i. External intercostals 1. Extend from tubercles of ribs to costochondral junctions 2. Run inferoanteriorly from superior rib to inferior rib 3. Continuous with external oblique abdominal muscle anteriorly 4. Incomplete anteriorly ii. Internal intercostals 1. Run deep to and at 90° angle form external intercostals 2. From ribs and costal cartilages to sternum 3. Continuous with internal oblique abdominal muscle anteriorly 4. Incomplete posteriorly Section 2  5 iii. Innermost intercostals 1. Separated from internal intercostals by the intercostal neurovascular bundle 2. Span the internal surfaces of adjacent ribs iv. Subcostalis 1. Spans 2-3 levels, originates near angle of lower ribs 2. Deep to innermost v. Transverse thoracis 1. Continuous inferiorly with transverse abdominus muscle vi. Levator costarum (is typically included with the intrinsic back muscles, see next section) Know the location and layering of these muscles. Do NOT worry about specifics of attachments Section 2  6 b. Neurovascular Supply to Intercostals i. The neurovascular supply runs between the internal and innermost layers of the intercostals in the costal groove. 1. From superior to inferior the structures are vein, artery, nerve (VAN) ii. Innervation: Segmental APRs iii. Arterial Supply 1. Space 1-2: Superior/supreme intercostal aa (off 1st part of axillary) 2. Spaces 3-7: intercostal arteries 3. Inferior to rib 8: musculophrenic (off internal thoracic) iv. Venus Drainage: intercostal veins Section 2  7 5. Intrinsic Back Muscles a. Superficial Intrinsics i. Splenius Cervicis ii. Splenius Capitus Muscle Origin Insertion Action Innervation Mastoid Process (temporal bone) Lateral flexion Splenius Lig Nuche Segmental Lat 1/3 sup nuchal line (occipital Ipsi rotation Capitus SP C7-T4 PPRs bone) (B) -> ext Lateral flexion Splenius Lig Nuche Post tubercles of Segmental Ipsi rotation Cervicis SP T3-T6 TPs C1-C4 PPRs (B) -> ext Section 3  8 b. Intermediate Intrinsics: Errector Spinae They arise from a common aponeurotic origin (part of the thoracolumbar fascia) that attaches to the iliac crest, sacrum, sacroiliac ligaments, and inferior lumbar and sacral spinous processes. The iliocostalis inserts into the angles of the ribs, the longissimus into the tips of the thoracic transverse processes and the spinalis the thoracic spinous processes and superior thoracic transverse processes. i. Iliocostalis (most lateral) 1. Lumborum 2. Thoracis 3. Cervicis ii. Longissimus (middle) 1. Thoracis 2. Cervicis 3. Capitus iii. Spinalis (most medial) 1. Thoracis 2. Cervicis 3. Capitus Section 3  9 Section 3  10 Erector Spinae (Intermediate Intrinsic Back Muscles) Muscle Origin Insertion Action Innervation angles of lower ribs and Bilateral: Iliocostalis cervical transverse Concentrically: processes Extend Arise by broad tendon vertebral from posterior part column and ribs between tubercles and iliac crest, posterior head against angles; surface of sacrum, gravity PPRs of transverse processes in Longissimus sacroiliac ligaments, Eccentrically: spinal thoracic and cervical supraspinous ligament Controls rate nerves region; and to mastoid and spinous processes of trunk flexion process of sacral and lower Isometrically: lumbar vertebrae Maintains spinous processes in the erect posture. Spinalis upper thoracic region and Unilateral: laterally flex to cranium trunk Section 3  11 Section 3  12 c. Deep Intrinsics: Transversospinal muscles i. Semispinalis: Spans 4-6 vertebral segments 1. Semispinalis thoracis 2. Semispinalis cervicis 3. Semispinalis capitus ii. Multifidus: spans 2-4 vertebral segments iii. Rotatores: spans 1-2 vertebral segments Deep Intrinsic Back Muscles Muscle Origin Insertion Action Innervation occipital bone and SP’s in PPRs of TP’s of C4-T12 thoracic and cervical Extension Semispinalis spinal vertebrae regions. Contralateral rotation nerves Span 4-6 segments posterior sacrum, PSIS, aponeurosis of erector Extension PPRs of Multifidus spinae, sacroiliac lig, SPs 2-4 segments superior Contralateral rotation spinal mamillary process of Stabilizes nerves lumbar vert Contralateral rotation PPRs of Lamina 1-2 segments Rotatores TPs Stabilizes spinal superior Proprioception? nerves superior aspect of SP’s Inferior aspect of SP’s PPRs of Aide in extension Interspinales in cervical and lumbar above spinal Proprioception? vertebrae nerves PPRs and Intertransver TP’s of cervical and TP’s of adjacent vertebrae Aide in lateral flexion APRs of sarii lumbar vert. Stabilizes spinal nerves Elevate ribs, assist with Levator Tips of TP’s of C7, T1- rib between tubercle and respiration, assist with PPRs C8-T11 Costarum T11 angle lat flexion Section 4  13 Section 4  14 d. Minor Deep Layer i. Interspinales: between SPs of adjacent segments ii. Intertransverserii: between TPs of adjacent segments iii. Levator costarum: TP to rib below 1. Assist with raising rib during inspiration Section 4  15 e. Actions of the Back Muscles i. Consider the actions of each muscle including its ability to rotate (contralateral or ipsilateral) and sidebend ii. Also think about how the muscles act eccentrically during functional activities 6. Anterior Muscles of the Vertebral Column (Prevertebral Muscles) a. Addressed in more detail with the neck and abdominal wall Section 4  16 7. Thoracolumbar Fascia: multiple layers of connective tissue a. Superficial i. Subcutaneous, may contain varying amounts of adipose tissue ii. Connected to deep fascia via fibrous septae b. Deep: Thoracolumbar Fascia i. Blends with the gluteal fascia and is continuous with the aponeuroses of the internal oblique abdominis and transversus abdominus muscles. ii. Composed of two to three laminae that envelope the intrinsic muscles of the back 1. Attachments from SPs and TP of vertebra: merge at lateral boarder of erector spinae 2. some also include the fascia surrounding the quadratus lumborum muscle as a division of the thoracolumbar fascia. iii. The functional significance of this thick layer of connective tissue is that it confers stability to the lumbar spine. As the back extensors contract, tension is transmitted to the thoracolumbar fascia as the muscles thicken. Section 5  17 Section 5  18 8. Innervation to the Back a. Muscles i. Extrinsics: 1. Muscles acting on the UE are innervated APRs via branches of the brachial plexus 2. Serratus posterior superior and inferior mm are innervated by ventral rami (APR’s) T2-5 and T9-12 ii. Intrinsics: 1. Innervated by segmental PPRs (other than the lateral portion intertransverserii which receive APRs) b. Connective Tissue i. Most connective tissue structures in the back and spine are innervated by segmental PPRs ii. Sinuvertebral nerves (recurrent meningeal nerves) innervate the outer portions of the intervertebral discs and related connective tissue Section 6