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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




      Circular muscle (sphincter)



      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



      Muscles can be classified by action

    Agonist (prime mover)





Names of skeletal muscles

      Names give clues to muscle characteristics


    Fascicle organization

    Relative position




    Origin and insertion



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


    Occipitofrontalis muscles



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)






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





Muscles of the vertebral column

      Neck region

    Longus capitus

    Longus colli

      Lumbar region

    Quadratus lumborum


Oblique and rectus muscles


    Scalene muscles

    Intercostal muscles

    Transverses muscles

      External and internal intercostals



Muscles of the pelvic floor


    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


    Deltoid muscles

    Supraspinatus muscles

      Medial rotators

    Subscapularis muscles

    Teres major muscles

      Lateral rotation

    Infraspinatus muscles

    Teres minor muscles


More shoulder movements

      Flexion and adduction


      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