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    Related Topics

    From Musculoskeletal System

    Acromioclavicular Joint
    The acromioclavicular joint connects the clavicle and scapula at the top of the shoulder, enabling smooth scapular motion and stability during arm movements.
    Nasal Bones
    Bones forming the bridge of the nose.
    Gomphoses
    Fibrous joints where a peg fits into a socket (e.g., teeth in jaw).
    Zygomatic Bones
    Cheekbones that form part of the orbit.
    Buccinator
    Muscle that helps with chewing and blowing air out.
    Frontal Bone
    Bone forming the forehead and upper part of the orbits.
    Diaphragm
    Primary muscle for breathing.
    Patella
    Knee cap, protecting the knee joint.
    Cervical Vertebrae (C1 - C7)
    Vertebrae in the neck region (C1-C7).
    Cranial Bones
    Bones of the skull that protect the brain.
    Biceps Brachii
    Muscle responsible for elbow flexion.
    Hyoid Bone
    U-shaped bone in the neck that supports the tongue.
    Humerus
    Upper arm bone connecting the shoulder to the elbow.
    Ethmoid Bone
    Bone forming part of the nasal cavity and the orbit.
    Sphenoid Bone
    Bone forming part of the base of the skull and sides of the orbits.
    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.
    Clavicle
    Collarbone connecting the arm to the body.
    Brachioradialis
    Muscle responsible for forearm flexion.
    Sacrum
    Triangular bone at the base of the spine.
    Maxillae
    Upper jaw bones that house the teeth and form part of the orbit.
    Hamstrings
    Biceps Femoris, Semitendinosus, Semimembranosus.
    Annular Ligament
    The annular ligament is a strong fibrous band encircling the head of the radius, stabilizing the proximal radioulnar joint and allowing smooth rotation of the forearm.
    Ischium
    Part of the pelvis that supports weight while sitting.
    Metacarpals (5 bones)
    5 bones forming the palm of the hand.
    Gastrocnemius
    Calf muscle responsible for plantarflexion of the foot.

    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.