Pectoralis Major and Minor, Serratus Anterior pt1

Overview of Muscles

Focus on the Pectoralis Major, Minor, and Serratus Anterior.

Pectoralis Major

  • Prominent chest muscle, visible in Arnold Schwarzenegger’s physique.

  • Contains divisions:

    • Clavicular fibers: Upper region.

    • Sternal fibers: Central region.

  • Key attachment at the crest of the greater tubercle of the humerus.

Bony Landmarks

  • Understanding the scapula is crucial:

    • Coracoid process: Protrudes near the lungs (1st and 2nd ribs).

    • Lateral & medial borders: Important for attachment of the serratus anterior.

  • Sternum anatomy:

    • Jugular notch: Above the sternoclavicular joint.

    • Manubrium: Uppermost portion of the sternum, separating from the body at the angle of Louis.

    • Xiphoid process: Cartilaginous projection at the base of the sternum, can vary in orientation.

    • Rib relationships: True ribs (1-7), false ribs (8-10), and floating ribs (11-12).

Intercostal Muscles

  • Internally and Externally Located:

    • Assist in respiration during inhalation and exhalation.

    • Important precaution needed when needling these areas to avoid puncturing the pleural cavity.

Muscle Interactions

Pec Major vs. Other Muscles

  • Muscles involved in shoulder movement:

    • Pectoralis major primarily responsible for internal rotation.

    • Competing with teres major/minor and infraspinatus for external rotation effectiveness.

  • Functional actions of the pectoralis major:

    • Upper fibers:

      • Flexion of the shoulder (lifting arm frontward).

      • Horizontal adduction (crossing arms).

    • Lower fibers: Limited shoulder extension capabilities.

Attachment Points

  • Origins:

    • Medial half of the clavicle, sternum, costal cartilages of first to sixth ribs.

  • Insertion: Crest of the greater tubercle of the humerus, facilitating internal rotation.

Palpation Techniques

  • Pectoralis Major:

    • Easily palpated in positions like supine or side-lying.

  • Pectoralis Minor:

    • More difficult to palpate; fibers run perpendicular to pec major fibers.

Clinical Relevance

  • Acupuncture points: Understanding anatomical landmarks necessary for effective treatment delivery.

    • Palpation of the sternum helps locate intercostal spaces.

  • Importance of proper technique while needling in sensitive rib areas to prevent discomfort or injury.