Muscles of the trunk: Origin, Insertion, Action
Deltoid Origin: Scapula & Clavicle Insertion: Deltoid tuberosity of humerus Action: Abduction at shoulder
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Diaphragm Origin: Xiphoid process, cartilage of ribs 4-10, anterior surfaces of lumbar vertebrae Insertion: Central tendinous sheet Action: Contraction expands thoracic cavity, compresses abdominopelvic cavity
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Erector spinae Origin: vertebral transverse & spinous processes, superior rib borders, iliac & sacral crests Insertion: vertebral transverse & spinous processes, upper ribs Action: stabilize & extend vertebral column
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External oblique Origin: Lower eight ribs Insertion: Linea alba & Iliac crest Action: Compresses abdomen, depresses ribs, flexes or laterally flexes vertebral column
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Infraspinatus Origin: Infraspinous fossa at scapula Insertion: Greater tubercle of humerus Action: Lateral rotation at shoulder
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Intercostals (External) Origin: Inferior border of each rib Insertion: Superior border of each rib Action: Elevates ribs
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Intercostals (Internal) Origin: Superior border of each rib Insertion: Inferior border of each rib Action: Depresses ribs
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Internal oblique Origin: Iliac crest and adjacent connective tissue Insertion: Lower ribs, xiphoid of sternum, and linea alba Action: Compresses abdomen, depresses ribs, flexes or laterall flexes vertebral column
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Latissimus dorsi Origin: Spinous process of lower thoracic vertebrae, ribs, and lumbar vertebrae Insertion: Intertubercular groove of humerus Action: Extension, adduction, and medial rotation of shoulder
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Pectoralis major Origin: Cartilages of the ribs 2-6, body of sternum, and clavicle Insertion: Greater tubercle of humerus Action: Flexion, adduction, and medial rotation of shoulder
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Rectus abdominus Origin: Superior surface of pubis around symphysis Insertion: Inferior surfaces of costal cartilage (ribs 5-7) and xiphoid process Action: Depresses ribs and flexes vertebral column
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Rhomboids Origin: Spinous process of lower cervical and upper thoracic vertebrae Insertion: Vertebral border of scapula Action: Adducts (retracts) and rotates scapula laterally (downward)
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Serratus anterior Origin: Anterior and superior margins of the ribs 1-9 Insertion: Anterior surface of vertebral border of scapula Action: Protracts shoulder, adducts and medially rotates scapula (upwards)
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Subscapularis Origin: Subscapular fossa at scapula Insertion: Lesser tubercle of humerus Action: Medial rotation at shoulder
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Supraspinatus Origin: Supraspinous fossa of scapula Insertion: Greater tubercle of humerus Action: Abduction at shoulder
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Teres major Origin: Inferior angle of scapula Insertion: Intertubercular groove of humerus Action: Adduction and medial rotation at shoulder
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Teres minor Origin: Lateral border of scapula Insertion: Greater tubercle of humerus Action: Lateral rotation at shoulder
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Transervsus abdominus Origin: Cartilages of lower ribs, iliac crest, & adjacent connective tissue Insertion: Linea alba and pubis Action: Compresses abdomen
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Trapezius Origin: Occipital bone and spinous process of thoracic vertebrae Insertion: Clavicle & Scapula Action: May elevate, adduct, depress, or rotate scapula and/or elevate clavicle; can also extend or hyper extend neck
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