Muscles of the Neck, Shoulders, Chest and Thorax

Muscles of the Neck, Shoulders, Chest and Thorax Sternocleidomastoid Platysma Trapezius Subscapularis Deltoid Pectoralis minor Pectoralis major Coracobrachialis Serratus anterior Biceps brachii Serratus anterior External oblique Rectus abdominus External oblique Linea alba Internal oblique Transversus abdominus Rectus abdominus Linea alba Muscles of the Neck, Shoulders, Chest and Thorax l. Superficial Muscles of the Neck, Shoulders and Upper Arm 1) Platysma (grimace muscle): a. Actions: helps depress the mandible b. Innervation: Facial Nerve (Vll) c. Origin: from skin over clavicle and fascia of pectoral and deltoid muscles d. Insertion: to margin of mandible 2) Sternocleidomastoid: a. Actions: head flexion and rotation b. Innervation: Accessory Nerve (Xl) c. Origin: from top of sternum (manubrium) and medial end of clavicle d. Insertion: to mastoid process of skull (temporal bone) 3) Trapezius (posterior): a. Actions: stabilizes, raises, retracts and rotates scapula abducts upper limbs b. Innervation: Accessory Nerve (Xl) c. Origin: from occipital bone down spinous processes through the thorax (ligamentum nuchae) d. Insertion: along the acromion and spine of the scapula and later end of clavicle 4) Deltoid (antagonist of Pectoralis major and Latissimus dorsi) (arm swinging): a. Actions: anterior fibers flex and medially rotate arm, posterior fibers extend and laterally rotate arm b. Innervation: Accessory Nerve (Xl) c. Origin: from the lateral end of the clavicle and the acromium and spine of scapula d. Insertion: to deltoid tuberosity on the humerus 1 4 5 2 3 8 7 10 9 6 11 12 13 14 5) Biceps brachii a. Actions: flexes and supinates forearm (supinate rotates forearm laterally) – these act together for pulling tissue from tissue box, also a minor arm flexor b. Innervation: Musculocutaneous nerve c. Origin: from coracoid process and supraglenoid tubercle on scapula d. Insertion: through intertubercular groove of humerus to insert on radial tuberosity l. Muscles of the Shoulders and Chest 6) Serratus anterior (boxer’s muscle): a. Actions: holds scapula to chest wall and rotates it for arm abduction and forward motion (punching and pushing) b. Innervation: Long Thoracic Nerve (C5-7) c. Origin: from ribs 1-8 d. Insertion: to anterior surface of inside border (vertebral) of scapula 7) Pectoralis major (climbing, throwing pushing, forcing inspiration muscle): a. Actions: arm flexion, medial rotation, adducts arm (against resistance), 1 pulls ribcage down b. Innervation: Pectoral Nerve c. Origin: from clavicle, sternum, costal cartilage of ribs 1-6 4 d. Insertion: to greater tubercle of the humerus 2 8 7 8) Pectoralis minor: a. Actions: moves scapula down or ribcage up b. Innervation: Medial Pectoral Nerve (C6-8) c. Origin: from anterior of ribs 3-5 (beneath Pec. major) d. Insertion: to coracoid process of scapula 9) Coracobrachialis: a. Actions: flexion and adduction of humerus (like Pec. major) b. Innervation: Musculocutaneous Nerve c. Origin: from coracoid process of scapula d. Insertion: to medial surface of shaft of humerus 10) Subscapularis: a. Actions: medial rotator of humerus, stabilizes shoulder joint (holds the head of the humerus in the glenoid cavity) b. Innervation: Subscapular Nerve (C5-6) c. Origin: from subscapular fossa of the scapula d. Insertion: to lesser tubercle of the humerus 5 6 11 12 13 3 14 10 9 l. Muscles of the Chest and Thorax 11) External oblique (fibers run like hands in your pockets – down toward the center of the body): a. Actions: both sides together assists rectus abdominus in trunk flexion and compressing abdominal wall, individually does rotation and lateral flexion of trunk b. Innervation: Intercostal Nerves (T1-12) c. Origin: from outer surfaces of lower eight ribs d. Insertion: to linea alba via aponeurosis, pubic crest, tubercle, iliac crest 12) Internal oblique (fibers run opposite to External obliques): a. Actions: assists rectus abdominus in trunk flexion and compressing abdominal wall, acting alone rotates trunk b. Innervation: Intercostal Nerves (T1-12, L1) c. Origin: from iliac crest and inguinal ligament d. Insertion: to linea alba via aponeurosis and last 3 ribs 13) Transversus abdominus (fibers run horizontally): a. Actions: compresses abdominal cavity and organs inside b. Innervation: Intercostal Nerves (T7-12, L1) c. Origin: from inguinal ligament, iliac crest, lumbodorsal fascia and the cartilages of the last six ribs d. Insertion: to linea alba via aponeurosis and pubic crest 14) Rectus abdominus): a. Actions: trunk flexion (lumbar region), stabilizes pelvis during walking, increases intra-abdominal pressure, fixes and depresses ribs b. Innervation: Intercostal Nerves (T6-12) c. Origin: from pubic crest and symphysis d. Insertion: to xiphoid process, costal cartilages of ribs 5-7 1 4 5 2 8 7 6 11 12 13 3 14 10 9