Anatomy

56

The Muscular System

Objectives • Describe the arrangement of fascicles in various muscle types • Describe the classes of levers and how they relate to muscle function • Predict the actions of muscles based on their origins and insertions • Explain how muscles interact to produce or oppose movement • Explain how the muscle name can help identify its location, appearance, or function • Identify origin, insertion and action of selected skeletal muscles

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 called 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

57

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

58

List of Muscles and Function

Region View Muscle Function Facial Anterior/Oblique Occipitofrontalis front belly Raises eyebrows

Orbicularis oculi Closes eye Orbicularis oris Purses lips Zygomaticus minor/major Elevates & retracts lip and mouth Buccinator Compresses cheeks Depressor anguli oris Depress corner of mouth

Facial Lateral Masseter Elevate mandible/close jaw

Principle masticator Temporalis Elevates jaw, masticator

Neck Anterior Platysma Depress mandible, tense neck

Sternocleidomastoid Flex neck together Rotate head to opposite side alone

Anterior Omohyoid Depress hyoid & larynx deep section

Sternohyoid Depress hyoid & larynx Abdomen Anterior Rectus abdominis Vertebral flexion/compression

External oblique Vertebral flexion/rotation/comp deep section Internal oblique Vertebral flexion/rotation/comp deep section Transversus abdominis Compress abdomen deep section Diaphragm Quiet respiration

Shoulder Posterior Trapezius Elev/depress/adduct/up.rotation Girdle Serratus anterior Abduction, upward rotation

Rhomboid major/minor Adduction, downward rotation Anterior deep section Pectoralis minor Abduction, downward rotation

Shoulder Posterior Latissimus dorsi Adduct, inward rotation, extension Joint Teres major Adduct, inward rotation, extension

*Supraspinatus Abduction and stabilization *Infraspinatus Adduction, outward rotation *Teres minor Adduction, outward rotation

Anterior ribs removed *Subscapularis Adduction, inward rotation *Above four comprise the Rotator Cuff

Anterior Pectoralis major Flexion, inward rotation, Coracobrachialis Adduction, flexion Biceps brachii Flexion Triceps brachii long head Extension

Post/Lat/Ant Deltoid all fibers Abduct, ant. fibers in.rot/flex post. fibers outrot/flex Elbow Joint Anterior Biceps brachii Flexion, supination of hand

Brachialis Flexion Brachioradialis Flexion. Pro/supination to midpos.

Posterior Triceps brachii Extension

59

Region View Muscle Function Wrist & Hand Anterior Long Flexors

Flexor carpi radialis Flexion of wrist and hand Palmaris longus Flexion of wrist and hand Flexor carpi ulnaris Flexion of wrist and hand

Posterior Long Extensors Extensor carpi radialis long. Extension of wrist and hand Extensor digitorum Extension of wrist and hand Extensor carpi ulnaris Extension of wrist and hand

Hip Joint Anterior Iliopsoas

deep section Iliacus Flexion, outward rotation Psoas major Flexion, outward rotation

Quadriceps femoris Rectus femoris only Flexion

Sartorius Flexion, outward rotation Medial Gracilis Adduction

Pectineus Flexion, adduction Adductor longus Adduction, flexion

Posterior Gluteus maximus Extension, lateral rotation Hamstrings

Semitendinosus Extension Semimembranosus Extension Biceps femoris long head Extension

Lateral Tensor fasciae latae Iliotibial tract Flexion, stabilizes knee Gluteus medius Abduction

Knee Joint Anterior Quadriceps femoris

Rectus femoris Extension Vastus lateralis Extension Vastus medialis Extension

deep section Vastus intermedius Extension Posterior Hamstrings

Semitendinosus Flexion Semimembranosus Flexion Biceps femoris both heads Flexion

Sartorius Flexion Gracilis Flexion Gastrocmenius Flexion

Ankle Joint Anterior Tibialis anterior Dorsiflexion

Lateral Fibularis longus Eversion Posterior Gastrocnemius Plantarflexion

Soleus Plantarflexion

Be able to identify all of the above muscles on charts and models

60

Be able to identify actions for all of the above muscles Be able to also list the attachments (origin and insertion) for Bolded Muscles

Attachments are listed below

Principle Skeletal Muscles

Thoracic Muscles

Rectus Abdominus Origin: Pubis & Symphysis Pubis Insertion: Ribs & Sternum Action: Compresses abdomen, flexes vertebral column

External Obliques Origin: Lateral Ribs Insertion: Ilium & linea alba Action: Compress abdomen, rotates & laterally flexes

vertebral column

Internal Obliques Origin: Ilium & inguinal ligament Insertion: Lower ribs Action: Compresses abdomen, rotates & laterally flexes

vertebral column

Transverse Abdominus Origin: Ilium & lower ribs Insertion: Sternum, Linea alba, pubis Action: Compresses Abdomen for: forced experation,

micturition, defecation, emesis, & parturition

Diaphragm Origin: Dome shaped sheet, vertebrae, ribs & sternum Insertion: Central tendon Action: Floor of thoracic cavity

Resperation: contracts & flattens=inspiration Relaxes & rises=exhalation

Shoulder Girdle Muscles

Trapezius Flat sheet of muscle on upper back. Four muscles Origin: Occipital bone, ligamentum nuchae, C7-T12 spinous processes Insertion: Outer clavicle, spine & acromion of scapula Action: Elevation, Depression, Adduction & Up. Rot. of Scap.

Pectoralis Minor Small anterior, upper chest deep to pec major Origin: Ribs 3-5 near costal cartilage Insertion: Coracoid process of scapula Action: Depression, Abduction & Downward Rotation

Serratus Anterior Sawtoothed insertion Origin: Lateral ribs 1-8/9 Insertion: Entire anterior, medial border of scapula Action: Abduct & upward rotation of scapula

61

Shoulder Joint Muscles

Deltoid Origin: Acromion & spine of scapula, clavicle Insertion: Detloid tuberosity of humerus Action: Abducts, flexes, extends (horiz.) rotates (in. & out.)

Supraspinatus Origin: Supraspinous fossa of scapula Insertion: Top of greater tubercle of humerus Action: Abduction of shoulder joint <90°, prevents

dislocation Infraspinatus

Origin: Infraspinus fossa of scapula Insertion: Greater tubercle of humerus Action: Outward rotation, extension (horiz), adduction

Teres Minor Origin: Inferior lateral border of scapula Insertion: Greater tubercle of humerus (w/ infraspinatus) Action: Outward rotation, extension (horiz), adduction

Subscapularis Origin: Subscapular fossa of scapula Insertion: Lesser tubercle of humerus Action : Inward rotation

********** Above four muscles Rotator Cuff **********

Latissimus Dorsi Origin: T7-L5 spinous processes, Post. iliac crest & sacrum, Insertion: Medial border of intertubercular groove of humerus Action: Adduction, extension, inward rotation

Pectoralis Major Origin: Clavicle, Sternum, Costal cartilages of ribs 2 - 6 Insertion: Lateral border of intertubercular groove of humerus Action: Adduction, Extension

Horizontal Flexion

Teres Major Origin: Lateral border to inferior angle of scapula Insertion: Medial border of intertubercular groove of humerus Action: Adduction, Inward rotation, Extension

Elbow Joint Muscles

Biceps Brachii Actions at 3 joints Origin: Long Head: Supraglenoid tubercle of scapula

Short Head: Coracoid process of scapula Insertion: Radial tuberosity ** Display changes in length** Action: Flexes elbow, supinates hand,

Flexes shoulder joint (Long Head)

62

Brachialis "Upper Arm Muscle" Origin: Inferior, anterior humerus Insertion: Below coronoid process on the tuberosity of ulna Action: Flexion of elbow (workhorse of flexors)

Brachioradialis Origin: Lateral inferior humerus Inserton: Styloid process of radius Action: Elbow flexion (strongest at midposition)

Pronation & Supination to midposition

Triceps Brachii Origin: Long Head: Infraglenoid tubercle of humerus

Lateral & Medial Head: Post humerus Insertion: Olecranon of unla Action: Elbow extension

Extension of shoulder joint (long head) Muscles of Forearm of Wrist

Long Flexors Origin: Anterior medial epicondyle of humerus Inserion: Palmar surface of wrist & hand Action: Flexion of wrist & fingers

Long Extensors Origin: Posterior, lateral epicondyle of humerus Insertion: Dorsal surface of wrist & hand Action: Extension of wrist & fingers

Hip Joint Muscles

Iliopsoas Origin: Iliac fossa, sides of bodies T12-L5 vertebrae Insertion: Lesser trochanter of femur Action: Flexion & outward rotation of hip joint

Extension of lumbar vertebrae

Gluteus Maximus Origin: Posterior ilum, sacrum & cocyx Insertion: Lateral femur Action: Flexion & outward rotation of hip joint

Adductors Origin: Pubis Insertion: Medial & posterior femur Action: Adduction & outward rotation

Hamstrings - Biceps Femoris, Semimembranosus &Semitendinosus Origin: Ischial tuberosity Insertion: Biceps Femoris: Head of fibula & lateral tibia

Semimembranosus &Semitendinosus: Medial tibia Action: Extension of hip & flexion of knee

63

Sartorius (Longest) Tailor's Origin: ASIS Insertion: Medial tibial tuberosity Action: Flexes hip & knee

Gracilis

Origin: Symphysis pubis & pubis Inserton: Medial tibia Action: Adduction of hip

Knee Joint Muscles

Quadriceps Origin: Rectus Femoris: AIIS

Vastus Lateralis, Vastus Medialis, Vastus Intermedius: Femur Insertion: Tibial tuberosity via patellar ligament Action: Extension of knee (RF Hip Flex.)

Hamstrings Action: Flexion of knee

Ankle Joint Muscles

Gastrocnemius Origin: Posterior femoral epicondyles Inserton: Calcaneus via Achille's Tendon Action: Plantarflexion, knee flexion

Soleus Origin: Posterior tibia & fibula Insertion; Calcaneus via Achille's Tendon Action: Plantarflexion