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Anatomy Unit 5
Muscular System
| Term | Definition |
|---|---|
| Origin | attachment of a muscle's tendon to the stationary bone; usually proximal to the limbs |
| Insertion | attachment of a muscle's tendon to the movable bone; usually distal on the limbs |
| insertion; origin | _____ moves toward the ________ when the muscle contracts |
| muscle belly | thick, fleshy portion of the muscle between its tendons |
| action | main movements that occur when a muscle contracts |
| reverse muscle action | during some moments the usual roles switch; insertion stays fixed and origin moves |
| lever | rigid structure that moves around a fixed point; bones |
| Fulcrum | fixed point (joint) |
| effort | force that causes movement (muscle contraction) |
| load | resistance being moved (body part + any weight) |
| first class levers | fulcrum (e-f-l) |
| second class levers | load (f-l-e) |
| third class levers | effort (f-e-l) |
| parallel arrangement | fascicles run parallel to long axis of muscle |
| fusiform arrangement | fascicles nearly parallel to the long axis of the muscle |
| circular arrangement | fascicles are in concentric circles |
| triangular (convergent) arrangement | fascicles spread over a broad area and converge on a thick central tendon |
| pennate arrangement | short fascicles relative to total muscle length; tendon extends nearly the entire length of the muscle |
| unipennate arrangement | fascicles on only 1 side of the tendon |
| bipennate arrangement | fascicles on both sides of a centrally positioned tendon |
| multipennate arrangement | fascicles attach obliquely from many directions to several tendons |
| medial half of clavicle, sternum, and costal cartilages of ribs 2-6 | pectoralis major-origin |
| greater tubercle and lateral lip of inter tubercular sulcus of humerus | pectoralis major-insertion |
| adducts and medially rotates arm at shoulder | pectoralis major-action |
| medial and lateral pectoral nerves | pectoralis major-innervation |
| superior nuchal line of occipital bone, ligaments niche, spines of C7-T12 | trapezius-origin |
| lateral 3rd of clavicle, acromion, and spine of scapula | trapezius-insertion |
| superior fibers elevate scapula and help extend the head; middle fibers retract(adduct) scapula; inferior fibers depress scapula; superior and inferior fibers rotate scapula upward; stabilizes scapula | trapezius-action |
| accessory nerve (CN XI) | trapezius-innervation |
| spines of T7-L5, sacrum, iliac crest and ribs 9-12 (via thoracolumbar fascia) | latissimus dorsi-origin |
| intertubercular sulcus of humerus | latissimus dorsi-insertion |
| extends, adducts, and medially rotates arm at shoulder; draws arm inferiorly and posteriorly | latissimus dorsi-action |
| thoracodorsal nerve | latissimus dorsi-innervation |
| acromial end of clavicle, acromion, and spine of scapula | deltoid-origin |
| deltoid tuberosity of humerus | deltoid-insertion |
| adult arm | deltoid-action (lateral fibers) |
| flex and medially rotates arm | deltoid-action (anterior fibers) |
| extends and laterally rotates arm | deltoid-action (posterior fibers) |
| auxiliary nerve | deltoid-innervation |
| supraglenoid tubercle of scapula | biceps brachii-origin (long head) |
| coracoid process of scapula | biceps brachii-origin (short head) |
| radial tuberosity and bicipital aponeurosis | biceps brachii-insertion |
| flexes forearm at elbow; supinates forearm and flexes arm at shoulder | biceps brachii-action |
| musculocutaneous nerve | biceps brachii-innervation |
| infraglenoid tubercle of scapula | triceps brachii-origin (long head) |
| lateral and posterior surface of humerus | triceps brachii-origin (lateral head) |
| posterior surface of humerus | triceps brachii-origin (medial head) |
| olecranon of ulna | triceps brachii-insertion |
| extends forearm at elbow; long head extends arm at shoulder | triceps brachii-action |
| radial nerve | triceps brachia-innervation |
| Supraspinatus, infraspinatus, teres minor, subscapularis | 4 muscles of rotator cuff |
| supraspinous fossa | supraspinatus-origin |
| greater tubercle of humerus | supraspinatus-insertion |
| abducts arm; stabilizes glenohumeral joint | supraspinatus-action |
| supra scapular nerve | supraspinatus-innervation |
| infraspinous fossa | infraspinatus-origin |
| greater tubercle of humerus | infraspinatus-insertion |
| laterally rotates arm; stabilizes glenohumeral joint | infraspinatus-action |
| supra scapular nerve | infraspinatus-innervation |
| inferior lateral border of scapula | teres minor-origin |
| greater tubercle of humerus | teres minor-insertion |
| laterally rotates and extends arm; stabilizes glenhumeral joint | teres minor-action |
| auxiliary nerve | teres minor-innervation |
| sub scapular fossa | subscapularis-origin |
| lesser tubercle of humerus | subscapularis-insertion |
| medially rotates arm; stabilizes glenohumeral joint | subscapularis-action |
| upper and lower sub scapular nerves | subscapularis-innervation |
| mechanical advantage | load is closer to the fulcrum than the effort |
| mechanical disadvantage | load farther from the fulcrum than the effort |
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auweb921
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