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    Related Topics

    From Musculoskeletal System

    Flexor and Extensor Groups
    Muscles responsible for flexing and extending the hand and wrist.
    Rectus Abdominis
    Abs muscle that flexes the trunk.
    Tibialis Anterior
    Muscle that dorsiflexes and inverts the foot.
    Ball-and-Socket Joints
    e.g., shoulder, hip
    Trapezius
    Muscle responsible for moving, rotating, and stabilizing the scapula.
    Coracoacromial Ligament
    Ligament that connects the acromion to the coracoid process.
    Sacroiliac Ligaments
    Ligaments connecting the sacrum to the iliac bones.
    Soleus
    Calf muscle responsible for plantarflexion of the foot.
    Sartorius
    Longest muscle in the body responsible for hip flexion.
    Extensor Tendons
    Tendons that help extend the fingers and toes.
    Anterior Cruciate Ligament (ACL)
    Knee ligament that stabilizes the joint.
    Rotator Cuff Tendons
    Tendons of the rotator cuff muscles.
    Metatarsals (5 bones)
    5 bones forming the mid-foot.
    Anterior Longitudinal Ligament
    Spinal ligament running along the front of the vertebral column.
    Wormian Bones
    Sutural bones in the skull.
    Levator Ani
    Pelvic floor muscle responsible for lifting the anus.
    Metacarpals (5 bones)
    5 bones forming the palm of the hand.
    Achilles Tendon
    Tendon connecting the calf muscle to the heel bone.
    Humerus
    Upper arm bone connecting the shoulder to the elbow.
    Gomphoses
    Fibrous joints where a peg fits into a socket (e.g., teeth in jaw).
    Temporal Bones
    Bones forming the lower sides of the skull and housing the ears.
    Brachioradialis
    Muscle responsible for forearm flexion.
    Radius
    Forearm bone on the thumb side.
    Ribs (12 Pairs)
    12 pairs of bones that form the sides of the thoracic cage.
    Ligamentum Flavum
    Spinal ligament connecting the laminae of adjacent vertebrae.

    Pectoralis Major

    Reviewed by our medical team

    Chest muscle responsible for shoulder movement.

    1. Overview

    The pectoralis major is a large, fan-shaped, superficial muscle located on the anterior chest wall. It is one of the most powerful muscles of the upper body and plays a primary role in movements of the shoulder joint, particularly adduction and medial rotation of the humerus. It contributes to the contour of the chest and is significant in both functional movement and aesthetic musculature.

    2. Location

    The pectoralis major is found on the anterior thoracic wall:

    • Medially: Originates from the sternum and the medial portion of the clavicle.

    • Laterally: Inserts into the upper humerus (intertubercular sulcus).

    • Superficial to: The pectoralis minor and the upper ribs.

    • Forms: The anterior wall of the axilla (armpit).

    3. Structure

    The pectoralis major is a thick, triangular muscle composed of two heads:

    • Clavicular head: Originates from the medial half of the clavicle.

    • Sternocostal head: Originates from the anterior surface of the sternum, costal cartilages of ribs 1–6 (or 1–7), and the aponeurosis of the external oblique muscle.

    • Insertion: Both heads converge to insert on the lateral lip of the intertubercular groove (bicipital groove) of the humerus.

    • Innervation: Lateral and medial pectoral nerves (C5–T1).

    • Blood supply: Primarily from the thoracoacromial artery and lateral thoracic artery.

    4. Function

    The pectoralis major has several primary functions involving the upper limb:

    • Adduction of the humerus: Brings the arm toward the midline of the body.

    • Medial (internal) rotation: Rotates the humerus inward.

    • Flexion of the humerus: Especially by the clavicular head; assists in lifting the arm forward.

    • Extension of the flexed humerus: The sternocostal head helps bring the arm back to the anatomical position from a flexed position.

    5. Physiological role(s)

    Beyond basic movement, the pectoralis major supports several functional processes:

    • Assists in respiration: Can act as an accessory muscle of inspiration when the arms are fixed, helping expand the thoracic cage.

    • Stabilizes the shoulder joint: Works with surrounding musculature to hold the humeral head in place.

    • Contributes to posture: Influences scapular and thoracic positioning during static and dynamic activity.

    • Enables pushing strength: Essential for activities like pushing open a door, performing push-ups, or throwing.

    6. Clinical Significance

    The pectoralis major can be involved in a variety of medical and athletic conditions:

    • Muscle tear or rupture:

      • Most commonly occurs in weightlifters during eccentric loading (e.g., bench press).

      • Presents with pain, bruising, weakness in arm adduction, and visible deformity of the chest wall.

      • Complete ruptures often require surgical repair.

    • Poland syndrome:

      • A congenital condition involving underdevelopment or absence of the pectoralis major (usually unilateral), often with ipsilateral hand abnormalities.

    • Pectoral muscle tightness:

      • Shortening of the muscle from poor posture or overuse can lead to shoulder protraction and upper-crossed syndrome.

    • Electromyography (EMG) testing:

      • Used to assess nerve conduction and muscle activity in cases of brachial plexus injuries or thoracic outlet syndrome.

    • Surgical reconstruction:

      • May be used as a flap in reconstructive surgeries (e.g., pectoralis major flap in head and neck surgery).

    Did you know? Your thumb has two phalanges, whereas other fingers have three.