Upper Limbs

Transition from Lower Limb to Upper Limb

  • Move from lower limb musculoskeletal discussion to upper limb

  • Focus on shoulder muscles and muscles that move the humerus

  • Plan to cover shoulder muscles first, then muscles acting on humerus moving towards the elbow

Complexity of Upper Limb Musculature

  • The upper limb musculature is considered more complex than that of the lower limb due to three main reasons:

    • Attachment to the Axial Skeleton:

      • Direct attachment only at the clavicle to the sternum.

    • Muscle Flexibility:

      • Wide range of motion necessitates more complex muscle formations.

      • Muscles often perform multiple actions for scapula stability and movement.

    • Brachial Plexus:

      • Innervation complexity with five terminal nerves, making quadrant classification of nerves challenging.

Current Focus on Scapula Movements

  • Scapula movements include:

    • Elevation

    • Depression

    • Protraction

    • Retraction

    • Superior rotation

    • Inferior rotation

Combination of Muscular Actions

  • Simultaneous Contraction:

    • All muscles attach to scapula contract together to stabilize the scapula resulting in little to no movement.

  • Isolated Contraction:

    • Specific muscles contract for singular actions demonstrating synergism among muscles.

  • Sequential Contraction:

    • Muscles contract in an ordered sequence, essential for specific movements of the scapula.

Chart for Scapula Movements

  • Elevation:

    • Action: Elevate;

    • Muscles: Trapezius (upper), Levator Scapulae, Rhomboids

  • Depression:

    • Action: Depress;

    • Muscles: Trapezius (lower), Pectoralis Minor

  • Protraction:

    • Action: Protract;

    • Muscles: Serratus Anterior, Pectoralis Minor

  • Retraction:

    • Action: Retract;

    • Muscles: Trapezius (middle), Rhomboids

  • Superior Rotation:

    • Action: Superiorly rotate scapula;

    • Muscles: Upper Trapezius, Lower Trapezius, Serratus Anterior

  • Inferior Rotation:

    • Action: Inferiorly rotate scapula;

    • Muscles: Rhomboids, Levator Scapulae, Pectoralis Minor

Individual Muscles of the Scapula

  • Trapezius:

    • Shape: Trapezoid, has attachment points from the occipital bone to spine of the scapula.

    • Functions:

    • Extension of the neck

    • Elevates, retracts, depresses, and superiorly rotates scapula.

    • Innervation:

    • Cranial Nerve XI (Spinal Accessory).

  • Serratus Anterior:

    • Appearance: Serrated knife shape, located from ribs 1 to 9.

    • Functions:

    • Protraction and some depression of scapula.

  • Levator Scapulae:

    • Origin: Transverse processes of cervical vertebrae.

    • Functions:

    • Elevates scapula.

  • Rhomboids (Major and Minor):

    • Attach from spinous process to medial border of scapula.

    • Functions:

    • Elevate and retract scapula, assist in inferior rotation.

  • Pectoralis Minor:

    • Location: Beneath Pectoralis Major, from ribs 3-5 to coracoid process.

    • Functions:

    • Protracts, depresses, and aids in inferior rotation of scapula.

Rotator Cuff Muscles

  • Rotator Cuff Overview:

    • Stabilizes and facilitates rotation of humerus; muscles attach to scapula but move humerus.

  • Muscle List (SITS):

    • Supraspinatus:

    • Action: Abduction of humerus.

    • Innervation: Suprascapular nerve.

    • Infraspinatus:

    • Action: Lateral rotation of humerus.

    • Innervation: Suprascapular nerve.

    • Teres Minor:

    • Action: Lateral rotation of humerus.

    • Innervation: Axillary nerve.

    • Subscapularis:

    • Action: Medial rotation of humerus.

    • Innervation: Subscapular nerve.

Shoulder and Elbow Movement Nerves

  • Innervating Nerves of Brachial Plexus:

    • Ventral Nerves (Flexors):

    • Musculocutaneous, Median, Ulnar nerves.

    • Dorsal Nerves (Extensors):

    • Radial and Axillary nerves.

  • Quadrant System:

    • Utilize actions to classify muscles rather than by nerve integration due to complexity.

  • Muscle Actions at the Shoulder:

    • Medial: Adduction

    • Lateral: Abduction

    • Anterior: Flexion

    • Posterior: Extension

Transition to Humerus Movement

  • Transition focus to muscles assisting elbow and shoulder movements.

  • Detailed plans to fill out quadrant charts concentrating on synergistic muscle actions and anatomical attachments.