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    Related Topics

    From Musculoskeletal System

    Trapezius
    Muscle responsible for moving, rotating, and stabilizing the scapula.
    Temporal Bones
    Bones forming the lower sides of the skull and housing the ears.
    Frontal Bone
    Bone forming the forehead and upper part of the orbits.
    Diaphragm
    Primary muscle for breathing.
    Gastrocnemius
    Calf muscle responsible for plantarflexion of the foot.
    Vomer Bone
    Bone forming the nasal septum.
    Hamstrings
    Biceps Femoris, Semitendinosus, Semimembranosus.
    Maxillae
    Upper jaw bones that house the teeth and form part of the orbit.
    Cranial Bones
    Bones of the skull that protect the brain.
    Mandible
    Lower jawbone that houses the teeth.
    Pubis
    Part of the pelvis that joins with the opposite side to form the pubic symphysis.
    Brachioradialis
    Muscle responsible for forearm flexion.
    Cervical Vertebrae (C1 - C7)
    Vertebrae in the neck region (C1-C7).
    Sartorius
    Longest muscle in the body responsible for hip flexion.
    Rotator Cuff Muscles
    Supraspinatus, Infraspinatus, Teres Minor, Subscapularis.
    Abductor Digiti Minimi Muscle
    The abductor digiti minimi muscle is a hypothenar muscle that abducts and flexes the little finger, aiding grip and precision in hand movements.
    Ulna
    Forearm bone on the pinky side.
    Flexor and Extensor Groups
    Muscles responsible for flexing and extending the hand and wrist.
    Ellipsoidal (Condyloid) Joints
    e.g., wrist
    Soleus
    Calf muscle responsible for plantarflexion of the foot.
    Anterior Scalene Muscle
    The anterior scalene muscle is a deep neck muscle that elevates the first rib during inspiration and aids in neck flexion and stability, located between key neurovascular structures.
    Fibula
    Smaller bone in the lower leg, located alongside the tibia.
    Pelvic Floor Muscles
    Muscles that support pelvic organs.
    Hinge Joints
    e.g., elbow, knee
    Anterior Longitudinal Ligament
    Spinal ligament running along the front of the vertebral column.

    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? The sternocleidomastoid muscle helps rotate the head.