anatomy quiz

• Muscles of the Pectoral Region

  Also known as Anterior Axio-appendicular Muscles / Thoraco-appendicular muscles, move the pectoral girdle, containing the pectoralis major, pectoralis minor, subclavius, and serratus anterior muscles.

  
• Pectoralis Major Muscle


  • Origin: Medial 2/3rd anterior surface of clavicle, anterior surface of sternum, first seven costal cartilages, aponeurosis of external oblique. Insertion: Lateral lip of intertubercular groove. Innervation: Medial and lateral pectoral nerves. Actions: Adduction, medial rotation, and flexion of the humerus at the shoulder joint.

  
• Pectoralis Minor Muscle


  • Origin: Anterior surfaces of the third, fourth and fifth ribs near costal cartilages, and deep fascia overlying the related intercostal spaces. Insertion: Medial border and superior surface Coracoid process of scapula. Innervation: Medial pectoral nerves. Actions: Depresses tip of shoulder; protracts scapula. Stabilizes scapula by drawing it inferiorly and anteriorly against thoracic wall.

  
• Subclavius Muscle


  • Origin: First rib at the junction between rib and costal cartilage. Insertion: Groove on inferior surface of middle third of clavicle. Innervation: Nerve to subclavius. Actions: Pulls clavicle medially to stabilize sternoclavicular joint, anchors and depresses clavicle.
• Serratus Anterior


  • Origin: Lateral surfaces of upper 8-9 ribs and deep fascia overlying the related intercostal spaces. Insertion: Costal surface of medial border of scapula. Innervation: Long thoracic nerve [C5,C6,C7]. Action: Protraction and rotation of the scapula, keeps medial border and inferior angle of scapula opposed to thoracic wall.

  
• Deltoid Muscle


  • Origin: Anterior border of Lateral one third of the clavicle, acromion, spine of scapula. Insertion: Middle of lateral surface of shaft of humerus (Deltoid tuberosity). Nerve Supply: Axillary nerve (C5,6). Action: Abducts arm, anterior fibers flex and medially rotate arm, posterior fibers extend and laterally rotate arm.

  
• Supraspinatus Muscle


  • Origin: Supraspinous fossa of scapula. Insertion: Greater tuberosity of humerus; capsule of shoulder joint. Nerve Supply: Suprascapular nerve (C4, 5,6). Action: Abducts arm and stabilizes shoulder joint.

  
• Infraspinatus Muscle


  • Origin: Infraspinous fossa of scapula. Insertion: Greater tuberosity of humerus; capsule of shoulder joint. Nerve Supply: Suprascapular nerve (C4, 5,6). Action: Laterally rotates arm and stabilizes shoulder joint.

  
• Teres Major Muscle


  • Origin: Lower third of lateral border of scapula. Insertion: Medial lip of bicipital groove of humerus. Nerve Supply: Lower subscapular nerve (C6,7). Action: Medially rotates and adducts arm and stabilizes shoulder joint.

  
• Teres Minor Muscle


  • Origin: Upper two thirds of lateral border of scapula. Insertion: Greater tuberosity of humerus; capsule of shoulder joint. Nerve Supply: Axillary nerve (C4, C5,6). Action: Laterally rotates arm and stabilizes shoulder joint.

  
• Subscapularis Muscle


  • Origin: Subscapular fossa. Insertion: Lesser tuberosity of humerus; capsule of shoulder joint. Nerve Supply: Upper and lower subscapular nerves (C5,6). Action: Medially rotates and adducts arm, stabilizes shoulder joint.

  
• Rotator Cuff Muscles


  The scapulohumeral muscles that form a musculotendinous rotator cuff around the glenohumeral joint, including the supraspinatus, infraspinatus, teres minor, and subscapularis muscles. They reinforce the fibrous layer of the joint capsule and provide stability to the shoulder joint.

  
• Suprascapular Nerve


  Originates from the superior trunk of the brachial plexus, passes posterolaterally through the suprascapular foramen to reach the posterior scapular region, innervates the supraspinatus and infraspinatus muscles.
• Axillary Nerve


  Originates from the posterior cord of the brachial plexus, leaves the axilla through the quadrangular space, enters the posterior scapular region, innervates the deltoid and teres minor muscles, and has a cutaneous branch called the superior lateral cutaneous nerve of the arm.