ap 10 muscular system

8/12/2019 AP 10 Muscular System

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THE MUSCULAR SYSTEM


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INTERACTIONS OF SKELETAL

MUSCLES IN THE BODY Muscles only pull; they are not capable of pushing

Generally as a muscle shortens, its insertion(attachment on the movable bone)moves toward itsorigin(its fixed or immovable point of attachment)

Muscles can be classified into four functional groups: 1.Prime Movers:

The muscle that provides the major force for the specific movementis called theprime mover or the agonist, of that movement

The biceps brachii muscle, which fleshes out the anterior arm (and inserts on the radius), is aprime mover of elbow flexion

2.Antagonists: Muscles that oppose or reverse a particular movement

When a prime mover is active, the antagonist muscles are often stretched and may berelaxed

Can also help to regulate the action of a prime mover by contracting to provide someresistance, thus helping to prevent overshoot or to slow or stop the movement

Prime mover and its antagonist are located on opposite sides of the joint acrosswhich they act

Antagonists can also be prime movers in their own right Example: flexion of the forearm by the biceps brachii muscle of the arm is antagonized by the

triceps brachii, the prime mover for extending the forearm


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MUSCLES IN THE BODY

3.Synergists: Help the prime movers by:

Adding a little extra force to the same movement

Or reducing undesirable or unnecessary movements that

might occur as the prime mover contracts When a muscle crosses two or more joints, its contraction

causes movement at all of the spanned joints unless othermuscles act as joint stabilizers

Example: the finger flexor muscles cross both the wristand the phalangeal joints, but you can make a fist without

bending your wrist because synergistic muscles stabilizethe wrist

As some flexors act, undesirable rotation movements occur

Synergists can prevent this, allowing all of the primemovers force to be exerted in the desired direction


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MUSCLES IN THE BODY

4.Fixators: when synergists immobilize

a bone, or a muscles origin, they are

more specifically called fixators

Examples:

Scapula is held to the axial skeleton only by

muscles and is quite freely movable

The fixator muscles that run from the axial skeleton to the

scapula can immobilize the scapula so that only the

desired movements occur at the mobile shoulder joint

Muscles that help to maintain upright posture


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MUSCLES IN THE BODY

Although prime movers seem to get all thecredit for causing certain movements,antagonistic and synergistic muscles are

also important in producing smooth,coordinated, and precise movements

A muscle may act as a prime mover inone movement, an antagonist foranother movement, a synergist for athird movement, and so on


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NAMING SKELETAL MUSCLES

1. Location of the muscle: Some muscle names indicate the bone orbody region with which the muscle is associated Example:

Temporalis muscle overlies the temporal bone

Intercostal muscles run between the ribs

2. Shape of the muscle: Some muscles are named for their shape Example:

Deltoid muscle is roughly triangular

Together the right and left trapezius muscles form a trapezoid

3. Relative size of the muscle: Terms such as maximus (largest),minimus (smallest), longus (long), and brevis (short) are often usedin muscle names to indicate relative size of the muscle Example:

Gluteus maximus

Gluteus minimus


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4. Direction of muscle fibers: The names ofsome muscles indicate the direction in whichtheir fibers (and fascicles) run in reference tosome imaginary line, usually the midline of the

body or the longitudinal axis of a limb bone Examples:

Rectus(straight): fibers run parallel to that imaginary line(axis)

Rectus femoris: straight muscle of the thigh, or femur)

Transversus(right angle): muscle fibers run at right angles Transversus abdominis: transverse muscle of the abdomen

Oblique(oblique angle): muscle fibers run at oblique angles External oblique: oblique muscle of the abdomen


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5. Number of origins: The number of

origins a muscle has may be indicated by

the word biceps, triceps, or quadriceps

Example:

Biceps brachii: muscle of the arm has two origins

(heads)


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6. Location of the attachments: Some

muscles are named according to the

location of their origin and insertion

Origin is always named first

Example:

Sternocleidomastoid: muscle of the neck

Has a dual origin on the sternum (sterno) and

clavicle (cleido), and it inserts on the mastoid

process of the temporal bone


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7. Action: A muscle may be named for its actionby using such words as flexor (flex), extensor(extend), adductor (brought toward), or supinate(bend backward) in its name Example:

Adductor longus: located in the medial thigh

Brings about thigh adduction (toward the main axis of the bodyor a limb)

Supinator muscle:

Supinates the forearm:

Turn the forearm or hand so that the palm faces upward

Supinates the leg and foot:

To rotate the foot and leg outward


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Several criteria are combined in the

naming of some muscles

Example: extensor carpi radialis longus Action of the muscle: the muscles action (extensor)

Location of attachment: joint it acts on (carpi = wrist)

Location of muscle: lies close to the radius of the

forearm (radialis)

Relative size of muscle: relative to other wrist extensormuscles (longus)

Unfor tunately, no t al l musc le names are this

descript ive


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MUSCLE MECHANICS:

IMPORTANCE OF FASCICLE ARRANGEMENT

AND LEVERAGE

In skeletal muscles the common

arrangement of the fascicles varies,

resulting in muscles with different shapes

and functional capabilities


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Arrangement of Fascicles

Fascicle: bundle of

nerve or muscle fibers

(cells) bound together

by connective tissue

All skeletal muscles

consist of fascic les, but

fascicle arrangement

vary, resulting in

muscles with differentshapes and functional

capabilities


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SKELETAL MUSCLE


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(a): Circular pattern: Fascicles arranged in

concentric rings

Muscles with thisarrangement surround

external openings, whichthey close by contracting

General term for thesemuscles is sphincters(squeezers)

Examples:

Orbicularis musclessurrounding the eyes(Orbicularis oculi) andthe mouth (Orbicularisoris)


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(b): Convergent pattern:

Muscle has a broad

origin, and its fascicles

converge toward a single

tendon of insertion Such a muscle is triangular

or fan shaped like the

pectoralis majormuscle

of the anterior thorax


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(c)(f): Parallel pattern: The long axes of the

fascicles run parallel tothe long axis of themuscle

Such muscles are either: straplike (c: parallel)

spindle (f: fusiform)

shaped with anexpanded belly(midsection)

Examples:

Sartoriusof thigh (c)

Biceps brachiimuscle ofthe arm (f)


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(d)(e)(g): Pennate pattern:

In a pennate (feather) pattern ofarrangement the fascicles are short andattach obliquely to a central tendon thatruns the length of the muscle

Types:

Unipennate: d

Fascicles insert into only oneside of the tendon

Example: extensor digitorummuscle of the leg

Bipennate: g

Fascicles insert into the tendonfrom opposite sides (musclegrains resemble a feather)

Example: rectus femoris muscleof the thigh

Multipennate: e

Arrangement looks like many

feathers situated side by side,with all their quills inserted intoone large tendon

Example: deltoid muscle, whichforms the roundness of theshoulder


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FASCICLE ARRANGEMENT

TO

MUSCLE STRUCTURE


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MUSCLE MECHANICS:

IMPORTANCE OF FASCICLE ARRANGEMENT

AND LEVERAGE The operation of most skeletal

muscles involves the use ofleverage and lever systems,partnerships between themuscular and skeletal systems Aleveris a rigid bar thatmoves

on a fixed point, or a fulcrum,

when a force is applied to it The applied force, or effort is used

to move a resistance or load

In your body, yourjoints act asthe fulcrums, the bones as thelevers, and the musclecontraction as the effort (force)

Load (resistance) is the boneitself, along with overlyingtissues and anything else youare trying to move with thatlever


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Lever Systems

A lever allows a given effort(force)to lift a heavier load(resistance),or to move aload (resistance) farther orfaster, than it otherwisecould

(a):First-Class: the load isclose to the fulcrum and theeffort is applied far from thefulcrum

A small effort exerted over arelatively large distance canbe used to move a large load

over a small distance Such a lever is said to

operate at a mechanic aladvantage and iscommonly ca lled a pow erlever


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Lever Systems

(b): Third-Class: Load is far from the

fulcrumand the effort isapplied near the fulcrum,the force exerted by themuscle must be greaterthan the load moved orsupported

This lever system operatesat a mechanicaldisadvantage and is aspeed lever

These levers are usefulbecause they providerapid contract ions wi th awide range of mot ion


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MUSCLE LEVERAGE


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Lever Systems

All levers follow the same basic principle: Effort fartherthan load from fulcrum = mechanical

advantage

Effort nearerthan load to fulcrum = mechanical

disadvantage Lever systems that operate at a mechanical

disadvantage (speed levers),force is lost butspeed and range of movement are gained,and this c an be a dist in ct benef i t

Lever systems that operate at a mechanicaladvantage (power levers) are slower, morestable, and used where streng th is a pr ior i ty


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Lever Systems

There are three

types of levers:

First-class

Second-class

Third-class


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Lever Systems

First-Class Levers (a): Effort is applied at one

end of the lever and the loadis at the other, with thefulcrum somewhere between

Examples:

Seesaws Scissors

Lift your head off your chest

Some operate at amechanical advantage

Others operate at amechanical disadvantage

Action of the triceps muscle inextending the forearm againstresistance (pushing)


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Lever Systems

Second-Class Levers (b): Effort is applied at one end

of the lever and the fulcrum islocated at the other, with theload between them

All second-class levers in the bodywork at a mechanical advantagebecause the muscle insertion(effort) is always farther from thefulcrum than is the load to bemoved

Levers of strength, but speedand range are sacrificed for thatstrength

Examples: Wheelbarrow

Uncommon in the human body Best example is the act of

standing on your toes


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Lever Systems

Third-Class Levers (c): Effort is applied between

the load and the fulcrum

Operate with great speed andalways at a mechanicaldisadvantage

Most skeletal muscles of the

body Tend to be thicker and more

powerful

Permits a muscle to be insertedvery close to the joint acrosswhich movement occurs

Allows rapid, extensivemovements with relatively little

shortening of the muscle Examples:

Tweezers (forceps)

biceps


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MUSCLE LEVERAGE


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Skeletal Muscles

Over 600

Book only list approximately 125 pairs of them


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ANTERIOR SUPERFICIAL

MUSCLES


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DIAGRAMMATIC VIEW

OF

ANTERIOR MUSCLES


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POSTERIOR VIEW

OF

SUPERFICIAL MUSCLES


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DIAGRAMMATIC VIEW

OF

POSTERIOR MUSCLES


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Facial Muscles

Muscles of the Head: Facial

Expression

Muscles of the scalp include

the epicranius consisting of

the frontalisand the

occipitalis Muscles of the face include

corrugator supercilii,

orbicularis oculi,

zygomaticus, risorius, levator

labii superioris, depressor labii

inferioris, depressor angulioris, orbicularis oris,

mentalis, buccinator, and

platysma


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MAJOR SKELETAL MUSCLES

OF

THE FACE Frontalis:cranial (facial nerve)

VII Raises the eyebrows (as in

surprise)

Wrinkles forehead skinhorixzontally

Cranial nerve VII

Orbicularis oculi:cranial (facialnerve) VII Protects eyes from intense light

and injury

Produces blinking, squinting

Draws the eyebrows inferiorly

Orbicularis oris:cranial (facialnerve) VII Closes lips

Purses (pucker) and protrudes(stick out) lips

Kissing and whistling muscle


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HEAD MUSCLES


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Muscles of the Head

Mastication and Tongue

Movement:

Muscles of mastication

include the masseter,

temporalis, medialpterygoid, lateral pterygoid,

and the buccinator

Muscles promoting tongue

movement are the

genioglossus,hypoglossus, and the

styloglossus


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Mastication Muscles

Masseter:Temporalis:cranial(trigeminal) nerve V

Prime mover of jaw closure

Elevates mandible

Temporalis:cranial (trigeminal)

nerve V Closes jaw

Elevates and retractsmandible

Buccinator:cranial (facial)nerve VII

Trampoline-like action

Keeps food between grindingsurfaces of teeth duringchewing


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Mastication Muscles


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HEAD MUSCLES


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Mastication Muscles


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Tongue Muscles

Genioglossus:cranial

(hypoglossal) nerve

XII

Primarily protrudestongue, but in concert

with other extrinsic

muscles to retract

tongue


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TONGUE MUSCLES



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OF

THE BODY

Muscles of the AnteriorNeck and Throat:Swallowing Suprahyoid muscles

include digastric,stylohyoid, mylohyoid, andgeniohyoid

Infrahyoid muscles includesternohyoid, sternothyroid,omohyoid, thyrohyoid, and

the pharyngealconstrictor muscles(superior, middle, andinferior)


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Neck and Throat Muscles

Mylohyoid:cranial

(trigeminal) nerve V

Elevates hyoid bone

and floor of mouth Enables the tongue to

exert backward and

upward pressure that

forces food bolus into

pharynx


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Neck and Throat Muscles

Pharyngealconstrictor muscles(superior, middle, andinferior):cranial

(vagus) nerve X Working as a group

and in sequence, allconstrict pharynx

during swallowing Propels food bolus

to esophagus peristalsis


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NECK MUSCLES


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NECK MUSCLES



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OF

THE BODY

Muscles of the Neck and Vertebral

Column: Head and Trunk Movement

Anterolateral neck muscles include the

sternocleidomastoid, and scalenes(anterior, middle, and posterior)

Intrinsic muscles of the back include splenius

capitis, erector spinae or sacrospinalis,iliocostals, longissimus, spinalis, semispinalis,

and the quadratus lumborum


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Neck Muscles

Sternocleidomastoid:cranial

(accessory) nerve XI and

branches of cervical nerves 2-

4:

Prime mover of head

flexion

Neck flexion

Head movement side-to-

side

NECK AND VERTEBRAL


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NECK AND VERTEBRAL

COLUMN MUSCLES

NECK AND VERTEBRAL


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NECK AND VERTEBRAL

COLUMN MUSCLES

NECK AND VERTEBRAL


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NECK AND VERTEBRAL

COLUMN MUSCLES


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Neck and Vertebral Column Muscles

Longissimus:

thoracis, cervicis, and

capitis: spinal nerves:

Capitis: extends headand turns face side to

side

Thoracis and

cervicis: extend

vertabral column side

to side

NECK AND VERTEBRAL


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NECK AND VERTEBRAL

COLUMN MUSCLES


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Thorax and Abdominal Muscles

Muscles of the Thorax: Breathing Muscles of the thorax include the external

intercostals, internal intercostals,and thediaphragm

Muscles of the Abdominal Wall: TrunkMovement and Compression of AbdominalViscera

Muscles of the anterolateral abdominal wallinclude the rectus abdominis, externaloblique, and the transversus abdominis


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Thorax Muscles

External intercostals:

intercostal nerves:

Elevate rib cage

Aids in inspiration

Internal intercostals:intercostal nerves:

Depress rib cage

Aids in expiration

Diaphragm:cervical(phrenic) nerve (C3-C5)

Breathing


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RESPIRATORY MUSCLES


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RESPIRATORY MUSCLES


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Abdominal Muscles

Rectus abdominis:Intercostal (thoracic)nerves: Flex and rotate lumbar

region

External oblique:Intercostal (thoracic)nerves: Compression of abdominal

wall

Transversus abdominis:Intercostal (thoracic)nerves: Compression of abdominal

wall


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ABDOMINAL MUSCLES


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ABDOMINAL MUSCLES



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OF

THE BODY

Muscles of the Pelvic Floor and Perineum:Support of Abdominopelvic Organs:

Muscles of the pelvic diaphragm include the

levator ani and the coccygeus Muscles of the urogenital diaphragm include

the deep transverse perineus and thesphincter urethrae

Muscles of the superficial space include theischiocavernosus, bulbospongiosus, andthe superficial transverse perineus

PELVIC FLOOR


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PELVIC FLOOR

AND

PERINEUM MUSCLES


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Pelvic Floor Muscles

Ischiocavernosus:pudendal (sacral) nerve:

Retards venou s d rainage

and maintains erect ion o f

penis or c l i tor is Bulbospongiosus:

pudendal (sacral) nerve:

Empties male urethra

Assist in erect ion of

penis in males and of

cl i tor is in females

PELVIC FLOOR


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AND

PERINEUM MUSCLES



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OF

THE BODY

Superficial Muscles of the Anterior and

Posterior Thorax: Movements of the

Scapula

Muscles of the anterior thorax include thepectoralis minor, serratus anterior, and the

subclavius

Muscles of the posterior thorax include thetrapezius, levator scapulae, and the

rhomboids (major and minor)



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OF

THE BODY

Muscles Crossing the Shoulder Joint:

Movement of the Arm

Muscles moving the arm include the

pectoralis major, latissimus dorsi, deltoid,subscapularis, supraspinatous,

infraspinatous, teres minor, teres major, and

the coracobrachialis


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Thorax Muscles

Deltoid: cervical nerves: Prime mover of arm abduction

Antagonists of pectoralis majorand latissimus dorsi

Pectoralis major: cervical andthoracic nerves: Prime mover of arm flexion

Adduction

Trapezius: cervical nerves: Stabilizes, raises, retracts, and

rotates scapula

Latissimus dorsi: cervical nerves Prime mover of arm extension

Powerful arm adductor Striking a blow

Swimming

Rowing


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THORAX MUSCLES


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SHOULDER MUSCLES



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OF

THE BODY

Muscles crossing the Elbow Joint: Flexion

and Extension of the Forearm

Posterior muscles include the t r iceps

brachii, and the anconeus Anterior muscles include the biceps

brach i i , brach ial is , and the b rachioradialis


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SHOULDER MUSCLES

Triceps brachii: cervicalnerves:

Powerful forearm extensor

Biceps brachii: cervicalnerves:

Flexes elbow joint andsupinates forearm

Brachialis: musculocutaneousnerve:

Major forearm flexor

Lifts ulna as biceps lifts the

radius Brachioradialis: radial nerve:

Synergist in forearm flexion


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SHOULDER MUSCLES


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SHOULDER MUSCLES


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O SC S


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ANTERIOR ARM MUSCLES

F M l


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Forearm Muscles

Extensor carpiradialis brevis: radialnerve: Extends and abducts

wrist Extensor digitorum:

branch of radialnerve:

Prime mover of fingerextension

Extends wrist

POSTERIOR ARM MUSCLES


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POSTERIOR ARM MUSCLES

ARM MUSCLES


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ARM MUSCLES

ARM MUSCLE ACTIONS


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ARM MUSCLE ACTIONS

ARM MUSCLE ACTIONS


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ARM MUSCLE ACTIONS



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OF

THE BODY

Muscles of the Forearm: Movements of the Wrist,Hand, and Fingers Anterior superficial muscles include the pronator teres, flexor

carpi radialis, palmaris longus, flexor carpi ulnaris, and the flexordigitorum superficialis

Anterior deep muscles include the flexor pollicis longus, flexordigitorum profundus, and the pronator quadratus

Posterior superficial muscles include the brachioradialis,extensor carpi radialis longus, extensor carpi radialis brevis,extensor digitorum, and the extensor carpi ulnaris

Posterior deep muscles include the supinator, abductor pollicislongus, extensor pollicis longus, and the extensor pollicis brevis



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OF

THE BODY

Intrinsic muscles of the Hand: FineMovements of the Fingers Thenar muscles in ball of thumb include the

abductor pollicis brevis, flexor pollicis brevis,opponnens pollicis, and the adductor pollicis

Hypothenar muscles in ball of little fingerinclude the abductor digiti minimi, flexor digiti

minimi brevis, and the opponens digiti minimi Midpalmar muscles include the lumbricals,

palmar interossei, and the dorsal interossei

H d M l


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Hand Muscles

Abductor pollicisbrevis: median nerve

(cervical.thoracic)

Abducts thumb

Flexor digiti minimi

brevis: ulnar nerve:

Flexes little finger

HAND MUSCLES


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HAND MUSCLES

HAND MUSCLES


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HAND MUSCLES


OF


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OF

THE BODY

Muscles Crossing the Hip and Knee Joints: Movements of the Thighand Leg Anteromedial muscles include the iliopsoas, which is composed of the

iliacus, the psoas major, and the sartorius

Muscles of the medial compartment of the thigh include the adductorgroup, which is made up of the adductor magnus, adductor longus andthe adductor brevis, the pectineus, and the gracilis

Muscles of the anterior compartment of the thigh include the quadricepsfemoris group, which is made up of the rectus femoris, vastus lateralis,vastus medialis and vastus intermedius, and the tensor fasciae latae

Posterior Muscles: gluteal muscles (origin on pelvis) include the gluteusmaximus, gluteus medius, and the gluteus minimus

Lateral rotators include the piriformis, obturator externus, obturator

internus, gemellus, and the quadratus femoris Muscles of the posterior compartment of the thigh include the hamstring

group, which consist of the biceps femoris, semitendinosus, and thesemimembranosus

Thi h M l


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Thigh Muscles

Adductor longus:obturator nerve: Adducts, flexes, and

medially rotates thigh

Gracilis: obturator nerve: Adducts thigh, flexes, and

medially rotates thigh,especially during walking

Quadriceps femoris: Rectus femoris: femoral

nerve: Extends knee and flexes

thigh at hip

ANTERIOR THIGH MUSCLES


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Hip Muscles


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Hip Muscles

Gluteus maximus:inferior gluteal nerve:

Major extensor of thigh

Complex, powerful, and

most effective when thighis flexed and force is

necessary, as in rising from

a forward flexed position

and in thrusting the thigh

posteriorly in climbing

stairs and running

Inactive during standing

POSTERIOR THIGH MUSCLES


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Hamstrings: sciaticnerve

Biceps femoris

Semitendinosus

Semimembranosus

Extends thigh and

flexes knee



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OF


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OF

THE BODY

Muscles of the Leg: Movements of the Ankle andToes Muscles of the anterior compartment include the tibialis anterior,

extensor digitorum longus, fibularis (peroneus) tertius, and theextensor hallucis longus

Muscles of the lateral compartment include the fibularis(peroneus) longus and the fibularis (peroneus) brevis

Superficial muscles of the posterior compartment include thetriceps surae, which is composed of the gastrocnemius and thesoleus, and the plantaris

Deep muscles of the posterior compartment include thepopliteus, flexor digitorum longus, flexor hallucis longus, and thetibialis posterior

ANTERIOR LEG MUSCLES


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Tibialis anterior: fibularnerve (lumbar): Prime mover of dorsiflexion

Inverts foot

Assists in supporting

medial longitudinal arch offoot

Fibularis longus: fibularnerve (lumbar): Plantar flexes and everts

foot May help keep foot flat on

ground



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LATERAL LEG MUSCLES


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LATERAL LEG MUSCLES

LATERAL LEG MUSCLES


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LATERAL LEG MUSCLES

POSTERIOR LEG MUSCLES


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Gastrocnemius: tibialnerve (sacral): Plantar flexes foot when

knee is extended

Since it also crosses knee

joint, it can flex knee whenfoot is dorsiflexed

Soleus: tibial nerve(sacral): Plantar flexes foot

Important locomotor andpostural muscle duringwalking, running, anddancing



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LEG MUSCLE ACTIONS


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LEG MUSCLE ACTIONS

LEG MUSCLE ACTIONS


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LEG MUSCLE ACTIONS


OF


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OF

THE BODY

Intrinsic Muscles of the Foot: Toe Movement andArch Support The muscle found on the dorsum of the foot is the extensor

digitorum brevis

Muscles on the sole of the foot found in the first layer are the

flexor digitorum brevis, abductor hallucis, and the abductor digitiminimi

Muscles on the sole of the foot found in the second layer are theflexor accessorius (quadratus plantae) and the lumbricals

Muscles of the sole of the foot found in the third layer include theflexor hallicis brevis, adductor hallucis, and the flexor digitiminimi brevis

Muscles of the sole of the foot found in the fourth layer includethe plantar and the dorsal interossei

Foot Muscles


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Dorsum

Extensor digitorumbrevis: fibular nerve

(sacral):

Helps extend toes

Foot Muscles


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Sole

Flexor digitorumbrevis: medial plantar

nerve (sacral):

Helps flex toes

FOOT MUSCLES


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FOOT MUSCLES

FOOT MUSCLES


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FOOT MUSCLES

FOOT MUSCLES


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FOOT MUSCLES

ap 10 muscular system

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