Chapter 11: The Muscular System – Appendicular Musculature Study Notes

Appendicular Musculature: Introduction

Overview of Appendicular Muscles

The appendicular musculature consists of muscles that stabilize and move the pectoral and pelvic girdles, as well as the upper and lower limbs. These muscles play essential roles in locomotion, shock absorption, and joint stabilization.

• Stabilization: Maintains the integrity of the pectoral and pelvic girdles.

• Movement: Responsible for moving the limbs.

• Shock Absorption: Absorbs impacts during activities such as walking, running, or jumping.

• Joint Strengthening: Reinforces joint areas to prevent injury.

Major Groups of Appendicular Muscles

• Pectoral girdle and upper limbs

• Pelvic girdle and lower limbs

Factors Affecting Appendicular Muscle Function

Action Lines of the Shoulder Joint

Action lines describe the direction of muscle pull and help determine the movement produced at a joint.

• Direction of Pull: The orientation of muscle fibers relative to the joint.

• Flexion/Extension: Movement that decreases/increases the angle at the shoulder.

• Adduction/Abduction: Movement toward/away from the midline.

• Medial/Lateral Rotation: Rotation toward/away from the body's midline.

Example: Deltoid Muscle

• Entire deltoid: Abduction at the shoulder

• Clavicular deltoid: Flexion and medial rotation

• Scapular deltoid: Extension and lateral rotation

Spurt and Shunt Muscles

Muscles are classified based on their insertion relative to the joint axis:

• Spurt Muscles: Insert close to the joint; produce rapid movement and torque (e.g., biceps brachii).

• Shunt Muscles: Insert farther from the joint; provide joint stability (e.g., brachioradialis).

Action Lines at the Hip Joint

• Flexion/Extension: Movement of the thigh forward/backward.

• Abduction/Adduction: Movement of the thigh away/toward the midline.

• Medial/Lateral Rotation: Rotation of the thigh inward/outward.

Muscles of the Pectoral Girdle and Upper Limbs

Functional Groups

• Muscles that position the pectoral girdle

• Muscles that move the arm

• Muscles that move the forearm and hand

• Muscles that move the hand and fingers

Muscles That Position the Pectoral Girdle

• Trapezius: Rotates scapula, extends neck

• Rhomboid: Adducts scapula

• Levator scapulae: Elevates scapula

• Pectoralis minor: Protracts shoulder

• Serratus anterior: Protracts scapula

• Subclavius: Protracts scapula

Muscles That Move the Arm

• Deltoid: Abducts arm

• Supraspinatus: Abduction at shoulder

• Infraspinatus: Lateral rotation at shoulder

• Subscapularis: Medial rotation at shoulder

• Teres major: Extension and medial rotation at shoulder

• Teres minor: Lateral rotation and adduction at shoulder

• Coracobrachialis: Adduction and flexion at shoulder

• Pectoralis major: Adducts, flexes, and medially rotates arm

• Latissimus dorsi: Extension, adduction, medial rotation at shoulder

• Rotator cuff: Supraspinatus, infraspinatus, subscapularis, teres minor

Muscles That Move the Forearm and Hand

• Extensor carpi ulnaris: Extension and adduction at wrist

• Triceps brachii: Extension at elbow

• Biceps brachii: Flexion at elbow, supinates forearm

• Brachialis: Flexion at elbow

• Brachioradialis: Flexion at elbow

• Anconeus: Extension at elbow

• Pronator teres: Pronates forearm

• Supinator: Supinates forearm

• Flexor carpi ulnaris: Flexion and adduction at wrist

• Flexor carpi radialis: Flexion and abduction at wrist

• Palmaris longus: Flexion at wrist

• Extensor carpi radialis longus/brevis: Extension and abduction at wrist

• Pronator quadratus: Pronates forearm and hand

Muscles That Move the Hand and Fingers

Extrinsic Muscles of the Hand

• Located mostly in the forearm

• Include: abductor pollicis longus, extensor digitorum, extensor pollicis brevis/longus, extensor indicis, extensor digiti minimi, flexor digitorum superficialis/profundus, flexor pollicis longus

• Tendons pass through synovial tendon sheaths in the wrist

Intrinsic Muscles of the Hand

• Located in the palm or dorsum of the hand

• Include: adductor pollicis, opponens pollicis, palmaris brevis, abductor digiti minimi, abductor pollicis brevis, flexor pollicis brevis, flexor digiti minimi brevis, opponens digiti minimi, lumbrical, dorsal interossei, palmar interossei

Compartments and Sectional Anatomy of the Arm and Forearm

Upper Arm Compartments

The deep fascia separates the soft tissues into compartments, each containing specific muscle groups.

Compartment	Muscles
Anterior compartment	Biceps brachii, Brachialis, Coracobrachialis
Posterior compartment	Triceps brachii

Forearm Compartments

Compartment	Muscles
Superficial anterior	Flexor carpi radialis, Flexor carpi ulnaris, Flexor digitorum superficialis, Palmaris longus, Pronator teres
Deep anterior	Flexor digitorum profundus, Flexor pollicis longus, Pronator quadratus
Lateral	Brachioradialis, Extensor carpi radialis brevis/longus
Posterior	Abductor pollicis longus, Anconeus, Extensor carpi ulnaris, Extensor digitorum, Extensor digiti minimi, Extensor indicis, Extensor pollicis brevis/longus, Supinator

Muscles of the Pelvic Girdle and Lower Limb

Overview

Lower limb muscles are larger and more powerful, divided into three groups:

• Muscles that move the thigh

• Muscles that move the leg

• Muscles that move the foot and toes

Muscles That Move the Thigh

• Gluteal group: Gluteus maximus (extension/lateral rotation), gluteus medius/minimus (abduction/medial rotation), tensor fasciae latae (extension of knee/lateral rotation of leg)

• Lateral rotator group: Obturator muscles, piriformis, gemelli, quadratus femoris (lateral rotation/abduction)

• Adductor group: Adductor brevis/longus/magnus, pectineus, gracilis (adduction, flexion, medial rotation)

• Iliopsoas group: Iliacus, psoas major (flexion at hip)

Muscles That Move the Leg

• Extensors of the knee (Quadriceps femoris): Vastus intermedius/lateralis/medialis, rectus femoris (extension at knee, flexion at hip)

• Flexors of the knee (Hamstrings): Biceps femoris, semimembranosus, semitendinosus (flexion at knee, extension at hip)

• Other flexors: Sartorius (flexes, abducts, laterally rotates hip), popliteus (medially rotates hip)

Muscles That Move the Foot and Toes

Extrinsic Muscles of the Foot

• Tibialis anterior: Dorsiflexion, inversion

• Gastrocnemius: Plantar flexion

• Fibularis brevis/longus: Plantar flexion, eversion

• Plantaris, soleus, tibialis posterior: Plantar flexion, inversion

• Flexor digitorum longus: Flexion of toes 2-5

• Flexor hallucis longus: Flexion of hallux

• Extensor digitorum longus: Extension of toes 2-5

• Extensor hallucis longus: Extension of hallux

Intrinsic Muscles of the Foot

• Abductor hallucis: Abduction of hallux

• Flexor digitorum brevis: Flexion of toes 2-5

• Abductor digiti minimi: Abduction of little toe

• Lumbricals: Extension of toes 2-5

• Flexor hallucis brevis: Flexion of hallux

• Flexor digiti minimi brevis: Flexion of little toe

• Quadratus plantae: Flexion of toes 2-5

• Adductor hallucis: Adduction of hallux

• Plantar interossei: Adduction of toes 3-5

• Extensor digitorum brevis: Extension of toes 1-4

• Dorsal interossei: Abduction of toes 3 and 4, extension of toes 2-4

Compartments and Sectional Anatomy of the Thigh and Leg

Thigh Compartments

• Anterior compartment

• Posterior compartment

• Medial compartment

Leg Compartments

• Anterior compartment

• Lateral compartment

• Superficial posterior compartment

• Deep posterior compartment

Additional info: The organization of muscles into compartments is clinically important for understanding compartment syndromes and the functional grouping of muscles for movement and stabilization.