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