Anatomy~ Chapter 12

Chapter 12: The Muscular System: Appendicular Musculature

Introduction

• Focuses on appendicular musculature utilized in upper and lower limbs.

• Overview of compartments and muscle functions.

Muscle Groups and Compartments

• Definition: Spaces enclosed by fasciae, known as intermuscular septa.

• Compartment Characteristics:

  • Includes one or more functionally related muscles.

  • Contains nerves and blood vessels.

• Upper Limbs:

  • Anterior and posterior compartments.

• Lower Limbs:

  • Anterior, posterior, medial, and lateral compartments.

Muscles Acting on the Arm (Anterior)

• Pectoralis Major:

  • Functions: Flexes, adducts, and medially rotates the humerus.

• Deltoid:

  • Versatile action: Can flex and medially rotate, abduct, or extend and laterally rotate the arm based on active fibers.

• Coracobrachialis:

  • Function: Flexes the arm and pulls it toward the trunk.

Muscles Acting on the Arm (Posterior)

• Teres Major:

  • Function: Extends and medially rotates the humerus.

• Latissimus Dorsi:

  • Functions: Adducts and medially rotates the humerus, extends the shoulder joint.

Rotator Cuff Muscles

• Muscles Involved:

  • Supraspinatus

  • Infraspinatus

  • Teres Minor

  • Subscapularis

• Mnemonic: Use the acronym SITS to remember these muscles.

Muscles Acting on the Forearm

• Brachialis:

  • Key function: Prime mover of elbow flexion.

• Biceps Brachii:

  • Functions: Supinates forearm and flexes both the elbow and shoulder.

• Brachioradialis:

  • Primary role: Flexes the elbow.

• Triceps Brachii:

  • Function: Extends the elbow.

Actions of the Rotator Muscles on the Forearm

• Supinator and Biceps Brachii:

  • Function: Supinate the forearm.

• Pronator Teres and Pronator Quadratus:

  • Function: Pronate the forearm.

Muscles of the Forearm: Anterior Compartment

• Function: Flex the wrist, fingers, and thumb.

• Key Muscles:

  • Tibialis Anterior

  • Extensor Digitorum Longus

  • Extensor Hallucis Longus

Muscles of the Forearm: Posterior Compartment

• Function: Extend the wrist, fingers, and thumb.

• Key Muscles:

  • Include various muscles involved in extension.

Muscles That Act on the Hip and Femur

• Iliopsoas:

  • Composed of Iliacus and Psoas Major, both responsible for flexing the thigh.

• Medial Compartment:

  • Contains Adductor muscles (magnus, brevis, longus) and Pectineus.

Anterior Muscles of the Thigh

• Quadriceps Femoris:

  • Purpose: Extends the knee.

  • Composed of four muscles:

    • Rectus Femoris

    • Vastus Lateralis

    • Vastus Medialis

    • Vastus Intermedius

• Sartorius:

  • Function: Flexes, weakly abducts, and laterally rotates the thigh.

Posterior Gluteal Muscles

• Gluteus Maximus:

  • Function: Extends and abducts the thigh.

• Gluteus Medius & Minimus:

  • Functions: Abduct and medially rotate the thigh.

Posterior (Flexor) Compartment of the Thigh

• Hamstring Muscles:

  • Function: Flex the knee.

  • Includes:

    • Biceps Femoris

    • Semitendinosus

    • Semimembranosus

Muscles of the Leg: Anterior Compartment

• Key Function: Dorsiflex the foot and extend the toes.

• Muscles:

  • Tibialis Anterior

  • Extensor Digitorum Longus

  • Extensor Hallucis Longus

Superficial Muscles of the Leg: Posterior Compartment

• General Function: Plantar flex the foot and flex the toes.

• Superficial Muscles:

  • Gastrocnemius

  • Soleus

• Deep Muscles:

  • Flexor Hallucis Longus

  • Tibialis Posterior

  • Flexor Digitorum Longus

Deep Muscles of the Leg: Lateral Compartments

• Function: Evert the foot.

• Key Muscles:

  • Fibularis Longus

  • Fibularis Brevis

Muscle Injuries

• Common causes: Sudden intense stress, improper conditioning, inadequate warm-ups.

• Initial Treatment: RICE method (Rest, Ice, Compression, Elevation).

• Example: Pulled hamstring involves strained posterior thigh muscles or partial tendon tears.

Selected Sports Muscle Injuries

• Pitcher’s Arm: Inflammation at wrist flexor attachments.

• Blocker’s Arm: Abnormal calcification due to impact in football.

• Shin Splints: Pain in the crural region, often linked with running activities.

• Tennis (Golfer’s) Elbow: Inflammation at attachment of extensor carpi muscles.