Muscles of the Shoulder, Arm, Forearm, and Hand

Exercise 15: Muscles of the Shoulder, Arm, Forearm, and Hand

Overview

• Muscular structure is crucial for movement and stabilization of the shoulder, arm, forearm, and hand.

1. Shoulder, Arm, Forearm, and Hand Models

• Anatomical models displaying:
  • Lateral view
  • Dorsal view
  • Medial view
  • Ventral view

2. Muscles Acting on the Shoulder

2.1. Anterior Thoracic Group

• Muscles:
  • Deltoid
  • Pectoralis major
  • Latissimus dorsi
  • Long head
  • Short head
  • Biceps brachii
  • Long head
  • Short head
  • Coracobrachialis
  • Subclavius
  • Subscapularis
  • Pectoralis minor
  • Trapezius
  • Serratus anterior
  • Teres major
• View: Anterior view
• Muscles cut for visibility in the diagram:
  • Deltoid, Pectoralis major

2.2. Posterior Thoracic Group

• Muscles:
  • Deltoid
  • Teres minor
  • Teres major
  • Latissimus dorsi
  • Trapezius
  • Levator scapulae
  • Rhomboideus minor
  • Rhomboideus major
• Other Muscles:
  • Supraspinatus
  • Infraspinatus
• View: Posterior view

3. Actions, Origins, Insertions, and Innervations of Shoulder Muscles

3.1. Table 15.1: Actions, Origins, Insertions, and Innervations

• Pectoralis Minor

  • Action: Protracts and depresses the scapula.
  • Origin: Ribs 3-5.
  • Insertion: Coracoid process of scapula.
  • Innervation: Medial and lateral pectoral nerve (C8-T1).

• Serratus Anterior

  • Action: Rotates and stabilizes the scapula.
  • Origin: Ribs 1-8.
  • Insertion: Medial border of scapula.
  • Innervation: Long thoracic nerve.

• Trapezius

  • Action: Elevates, retracts, and rotates the scapula.
  • Origin: Superior nuchal line of occipital bone; spinous processes of C7-T3.
  • Insertion: Acromion, spine of the scapula; lateral one-third of clavicle.
  • Innervation: Cranial Nerve XI and anterior rami of C3-C4.

• Rhomboideus Major & Minor

  • Action: Stabilizes scapula and lifts it.
  • Origin: C7 to T5.
  • Insertion: Medial border of scapula.
  • Innervation: Posterior scapular nerve.

4. Muscles Acting on the Arm

4.1. Muscles Overview

• Major muscles include:
  • Deltoid
  • Coracobrachialis
  • Biceps brachii
  • Long head
  • Short head
  • Triceps brachii
  • Brachialis
  • Brachioradialis
  • Latissimus dorsi

4.2. Actions, Origins, Insertions, and Innervations: Table 15.2

• Deltoid

  • Action: Abducts, flexes, and medially rotates arm.
  • Origin: Lateral third of the clavicle; acromion; spine of scapula.
  • Insertion: Deltoid tuberosity of humerus.
  • Innervation: Axillary nerve (C5-C6).

• Pectoralis Major

  • Action: Flexes, adducts, and medially rotates the humerus.
  • Origin: medial clavicle; costal cartilages of ribs 2-6; body of the sternum.
  • Insertion: Lateral intertubercular sulcus of humerus.
  • Innervation: Medial and lateral pectoral nerves.

• Biceps Brachii

  • Action: Flexes elbow, supinates forearm, slight shoulder flexion.
  • Origin: Short head from coracoid process; long head from superior margin of glenoid cavity.
  • Insertion: Radial tuberosity.
  • Innervation: Musculocutaneous nerve (C5-C6).

• Triceps Brachii

  • Action: Prime mover of elbow extension.
  • Origin: Long head from glenoid cavity; lateral head from proximal humerus; medial head from the entire shaft of humerus.
  • Insertion: Olecranon; fascia of forearm.
  • Innervation: Radial nerve.

5. Muscles with Bellies in the Arm (Brachium)

5.1. Major Muscles Overview

• Brachialis
  • Function: Prime mover of elbow flexion.
• Biceps brachii
  • Function: Synergist in elbow flexion;
• Triceps brachii
  • Function: Extends and adducts the arm.

5.2. Detailed Actions and Innervations (Table 15.3)

• Brachialis

  • Action: Flexes elbow.
  • Innervation: Musculocutaneous nerve.

• Biceps Brachii

  • Action: Flexes elbow, slight shoulder flexion, supinates forearm.
  • Innervation: Musculocutaneous nerve (C5-C6).

• Triceps Brachii

  • Action: Prime mover of elbow extension; extends and adducts arm.
  • Innervation: Radial nerve.

6. Muscles Acting on the Wrist and Hand

6.1. Compartment Overview

• Anterior (Flexor) Compartment:
  • Flexor carpi radialis
  • Flexor carpi ulnaris
  • Flexor digitorum superficialis
  • Flexor pollicis longus

6.2. Posterior (Extensor) Compartment:

• Extensor carpi radialis longus
• Extensor carpi radialis brevis
• Extensor digitorum
• Extensor digiti minimi
• Extensor carpi ulnaris

6.3. Actions, Origins, Insertions, and Innervations (Table 15.4)

• Flexor Carpi Radialis

  • Action: Flexes wrist anteriorly; aids in radial flexion.
  • Origin: Medial epicondyle of humerus.
  • Insertion: Base of metacarpals II-III.
  • Innervation: Median nerve.

• Flexor Carpi Ulnaris

  • Action: Flexes wrist anteriorly; aids in ulnar flexion.
  • Origin: Medial epicondyle.
  • Insertion: Pisiform, hamate, metacarpal V.
  • Innervation: Ulnar nerve.

• Flexor Digitorum Superficialis

  • Action: Flexes wrist, metacarpophalangeal, and interphalangeal joints.
  • Origin: Medial epicondyle of humerus; flexor retinaculum.
  • Insertion: Middle phalanges II-V.
  • Innervation: Median nerve.

7. Carpal Tunnel Syndrome

7.1. Description

• Narrow passageway situated on the palm side of the wrist.

7.2. Symptoms and Related Structures

• Related to flexor tendons, median nerve, and potential compression from swelling or structural abnormalities.

8. Intrinsic Muscles of the Hand

8.1. Major Groups

• Thenar Group: Responsible for thumb movements.
• Hypothenar Group: Responsible for movements of the little finger.
• Midpalmar Group: Responsible for movements of the fingers.

8.2. Actions, Origins, Insertions, and Innervations (Table 15.5)

• Adductor Pollicis

  • Action: Draws thumb toward palm.
  • Innervation: Ulnar nerve.

• Opponens Pollicis

  • Action: Opposes the thumb to fingertips.
  • Innervation: Median nerve.

• Dorsal Interosseous Muscles

  • Function: Abduct fingers; important for grip strength.
  • Innervation: Ulnar nerve.

Conclusion

• Detailed understanding of the intricate muscles of the shoulder, arm, forearm, and hand is essential for recognizing their functional roles and potential pathologies.