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University of Toronto Scarborough
Biological Sciences
Connie Soros

1 Lecture 6 The Muscular System Axial & Appendicular Musculature Introduction The skeletal muscle of the body can be subdivided into: Axial musculature Muscles that position the head and vertebral column Muscles that move the rib cage Appendicular musculature Muscles that stabilize or move the appendicular skeleton The Axial Musculature The axial muscles can be placed into four groups based on location or function Muscles of the head and neck Muscles of the vertebral column Oblique and rectus muscles Muscles of the pelvic floor Muscles of the Head and Neck Can be subdivided into several different groups Muscles of facial expression (mouth, eye, nose, scalp, neck) Extraocular muscles (muscles that control eye movement) Muscles of mastication (chewing) Masseter – elevates mandible and closes aws, assists in protracting nd retracting mandible and moving mandible from side to side (for mastication) Temporalis – elevates mandible and closed jaws, assists in retracting and moving mandible from side to side (right over the temporal bone) Medial Pterygoid – elevates the mandible and closes the jawa, or moves the mandible side to side • Lateral Pterygoid – opens jaws, protrudes mandible, or moves mandible side to side Muscles of the tongue Muscles of the pharynx (pharyngeal constrictors, laryngeal elevators, palatal muscles) Muscles of the anterior neck Digastric – depresses mandible, opening mouth, and/or elevates larynx Sternocleidomastoid –together they flex the neck, alone one side bends neck toward shoulder and turns face to the opposite side Sternohyoid – depresses hyoid bone and larynx Sternothyroid – depresses hyoid bone and larynx Thyrohyoid – elevates larynx depresses hyoid bone Stylohyloid – elevates larynx Muscles of the Vertebral Column Back muscles form three distinct layers Superficial layer (extrinsic back muscles): move the neck Trapezius – extends neck (will come back to more actions for this muscle) Latissimus dorsi – extension, adduction and medial rotation at shoulder, “swimmer’s muscle” Levator scapulae – elevates scapula Rhomboid muscles – adduct ad perform downward rotation of scapula © 2012 Pearson Education, Inc. 2 Intermediate layer (extrinsic back muscles): move the vertebral column Serratus posterior – Superior – elevates ribs, enlarges thoracic cavity; Inferior – pulls ribs inferiorly, also pulls outward opposing the diaphragm Deep layer (intrinsic back muscles): interconnect the vertebrae Can be further subdivided into: Superficial intrinsic Splenius muscles – two sides Act together to extend neck; either alone rotates and laterally flexes the neck to that side Intermediate intrinsic Erector spinae (group of three muscles) Spinalis group (most medial of the three) - extend neck and vertebral column Longissimus group - extend neck, rotate and laterally flex neck and extend vertebral column Iliocostalis group (most lateral of the three) – extend or laterally flex neck, elevate or depress ribs, stabilize and extend vertebral column Deep intrinsic Semispinalis – extend neck, turns head to opposite side and extend vertebral column and rotates toward opposite side Multifidus – same as above Rotatores – same as above Interspinales – extends vertebral column Intertransversarii – lateral flexion of vertebral column Oblique and Rectus Muscles These muscles can be grouped in this manner: Cervical oblique muscles (don’t need to know location) Scalene muscles (anterior, middle, and posterior scalenes) Elevate the ribs and also flex the neck Thoracic oblique muscles External intercostals: elevate the ribs, increase thoracic cavity and fills lungs Internal intercostals: depress the ribs, decrease thoracic cavity to help force air out of lungs Transversus thoracis: depresses the ribs Serratus posterior Superior serratus posterior: elevates ribs and enlarges thoracic cavity Inferior serratus posterior: depresses ribs and opposes diaphragm contract
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