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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

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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

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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

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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

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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)

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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

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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

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