The Muscular System

Muscle Organization and Function

Muscular system

• Includes all skeletal muscle tissue that can be controlled voluntarily

Organization of skeletal muscle fibers

• Parallel muscle

• Convergent muscle

• Pennate muscle

• Unipennate

• Bipennate

• Multipennate

• Circular muscle (sphincter)

Levers

• Rigid structure that moves on a fixed point, the fulcrum

• Changes direction and strength of applied force

• Changes distance and speed of movement

• Three classes

• First class

• Second class

• Third class

• Most common in the body

Muscle Terminology

Origins and Insertions

• Muscles can be identified by origin, insertion and action

• Origin = stationary end

• Insertion = movable end

Actions

• Muscles can be classified by action

• Agonist (prime mover)

• Antagonist

• Synergist

• Fixator

Names of skeletal muscles

• Names give clues to muscle characteristics

• Location

• Fascicle organization

• Relative position

• Structure

• Size

• Shape

• Origin and insertion

• Action

Axial and Appendicular Muscles

• Axial musculature arises on axial skeleton

• Positions head and spinal column and moves the rib cage

• Appendicular musculature moves and stabilizes components of the appendicular skeleton

The Axial Muscles

Axial muscles

• Logical groupings based on location and/or function

• Head and neck

• Vertebral column

• Oblique and rectus muscles

• Pelvic floor

Muscles of the head and neck

• Facial expression muscles

• Orbicularis oris

• Buccinator

• Occipitofrontalis muscles

• Platysma

Extrinsic eye muscles
(oculomotor or extra-ocular muscles)

• Inferior and superior rectus muscles

• Lateral and medial rectus muscles

• Inferior and superior oblique muscles

Muscles of mastication

• Masseter muscles

• Temporalis muscles

• Pterygoid muscles

Muscles of the tongue
(speech, swallowing and mastication)

• Genioglossus

• Hypoglossus

• Palatoglossus

• Styloglossus

Muscle of the pharynx

• Pharyngeal constrictors

• Laryngeal elevators

• Palatal muscles

Muscle of the neck

• Control the position of the larynx

• Depress the mandible

• Provide a foundation for the muscles of the tongue

• Digastric and sternocleidomastoid muscles

• Seven muscles that originate or insert on the hyoid

Muscles of the vertebral column

• Superficial muscles of the spine

• Spinalis

• Longissimus

• Iliocostalis

Muscles of the vertebral column

• Neck region

• Longus capitus

• Longus colli

• Lumbar region

• Quadratus lumborum

Oblique and rectus muscles

• Oblique

• Scalene muscles

• Intercostal muscles

• Transverses muscles

• External and internal intercostals

• Diaphragm

Muscles of the pelvic floor

• Perineum

• Anterior urogenital triangle

• Posterior anal triangle

• Pelvic floor

• Urogenital diaphragm

• Pelvic diaphragm

The Appendicular Muscles

Muscles of the shoulders and upper arms

• Trapezius muscles

• Affect the position of the shoulder girdle, head and neck

• Muscles inserting on the scapula

• Rhomboid muscles

• Levator scapulae muscles

• Serratus anterior muscles

• Subclavius muscles

• Pectoralis minor muscles

• Adductors

• Deltoid muscles

• Supraspinatus muscles

• Medial rotators

• Subscapularis muscles

• Teres major muscles

• Lateral rotation

• Infraspinatus muscles

• Teres minor muscles

More shoulder movements

• Flexion and adduction

• Coracobrachialis

• Flexion of the shoulder joint

• Pectoralis major muscles

• Extension of the shoulder joint

• Latissimus dorsi muscles

Muscles that affect the elbow

• Biceps brachii muscle

• Triceps brachii muscle

• Brachialis and brachioradialis flex the elbow

• Aconeus muscle extends the elbow

Muscles that affect the wrist

• Flexion of the wrist

• Flexor carpi ulnaris

• Flexor carpi radialis

• Palmaris longus

• Extension of the wrist

• Extensor carpi radialis

• Extensor carpi ulnaris

Muscles that affect the forearm

• Pronation of the forearm

• Pronator teres muscle

• Pronator quadratus muscle

• Supination of the forearm

• Supinator muscle

Muscles of the pelvis and lower limbs

• Gluteal muscles cover the lateral surfaces of the ilia

• Gluteus maximus (shares an insertion with the tensor fasciae latea)

• Pulls on the iliotibial tract

Lateral rotators of the leg

• Piriformis muscle

• Obturator muscles

Adductors perform a variety of functions

Iliopsoas muscle

• Formed from the merging of the psoas major and the iliacus muscles

• Powerful flexor of the hip

Flexors of the knee

• The hamstrings

• Biceps femoris muscles

• Semimembranosus muscles

• Semitendinosis muscles

• Popliteus muscle unlocks the knee joint

Extensors of the knee

• Quadriceps femoris

• Three vastus muscles

• Rectus femoris muscle

Movements at the ankle

• Plantar flexion

• Gastrocnemius muscle

• Soleus muscle

• Eversion and plantar flexion

• Fibularis muscle

• Foot position and toe movement is accomplished by muscles originating on the talus and metatarsal bones

Aging and the Muscular System

With aging

• Power and size of muscle tissue decrease

• Skeletal muscles undergo fibrolysis

• Tolerance for exercise decreases

• Repair of injuries slows