MUSCLES OF THE BODY Ch 11 Human Anatomy Sonya Schuh-Huerta, Ph.D. Leonardo Da Vinci

MUSCLES OF THE BODY MUSCLES OF THE BODY Ch 11Ch 11

Human AnatomyHuman Anatomy

Sonya Schuh-Huerta, Ph.D.Sonya Schuh-Huerta, Ph.D.

Leonardo Da Vinci

Muscles of the Body

• Skeletal muscles– Produce movements

• General principles of leverage

• Muscles act with or against each other

• Criteria used in naming muscles

Naming the Skeletal Muscles

• Location– Example the brachialis is located on the

arm (brachium)

• Shape– Example the deltoid is triangular

• Relative size– Maximus, minimus, & longus indicate size– Example gluteus maximus is the large one

& gluteus minimus is the small one

Naming the Skeletal Muscles

• Direction of fascicles & muscle fibers– Name tells direction in which fibers run– Example rectus abdominis & transversus

abdominis (rectus = straight up; transverse across or at right angle to midline)

• Location of attachments name reveals point of origin & insertion– Example brachioradialis

Naming the Skeletal Muscles

• Number of origins– 2, 3, or 4 origins – Indicated by the words biceps (2), triceps (3),

& quadriceps (4)

• Action– Action can be part of the muscle’s name– Indicates type of muscle movement

• Flexor, extensor, adductor, or abductor

(ie. extensor digitorum)

Arrangement of Fascicles in Muscles

• Skeletal muscles consist of fascicles– Fascicles arranged in different patterns– Fascicle arrangement tells about action of

a muscle

Arrangement of Fascicles in Muscles

• Types of fascicle arrangement– Parallel fascicles run parallel to the long

axis of the muscle• Strap-like sternocleidomastoid• Fusiform biceps brachii

Arrangement of Fascicles in Muscles

• Types of fascicle arrangement– Convergent

• Origin of the muscle is broad• Fascicles converge toward the tendon of insertion• Example Pectoralis major

Arrangement of Fascicles in Muscles

• Types of fascicle arrangement– Pennate

• Unipennate fascicles insert into one side of the tendon

• Bipennate fascicles insert into the tendon from both sides

• Multipennate fascicles insert into one large tendon from all sides

Arrangement of Fascicles in Muscles

• Circular– Fascicles are arranged in concentric rings

• Surround external body openings• Sphincter general name for a circular muscle• Examples

– Orbicularis oris & orbicularis oculi

(f) Bipennate (rectus femoris)

(a)

(b)

(c)

(f)

(g)

(e)

(d)

(a) Circular (orbicularis oris)

(b) Convergent (pectoralis major)

(d) Parallel (sartorius)

(c) Fusiform (biceps brachii)

(g) Unipennate (extensor digitorum longus)

(e) Multipennate (deltoid)

Arrangement of Fascicles in Muscles

Lever Systems: Bone-Muscle Relationships

• Movement of skeletal muscles involves leverage– Lever a rigid bar that moves – Fulcrum a fixed point– Effort applied force– Load resistance

Lever Systems

Load

Effort

Load

Effort

10kg

1000 kg

Fulcrum

10 x 25 = 1000 x 0.25 250 = 250

Effort x length of effort arm = load x length of load arm (force x distance) = (resistance x distance)

(a) Mechanical advantage with a power lever

Fulcrum

25 cm

0.25 cm

Lever Systems: Bone-Muscle Relationships

• Bones act as levers

• Joints act as fulcrums

• Muscle contraction provides effort– Applies force where muscle attaches to bone

• Load bone, overlying tissue, & anything being lifted

Lever Systems: Bone-Muscle Relationships

• Levers allow a given effort to– Move a heavier load– Move a load farther

Lever Systems: Bone-Muscle Relationships

• First-class lever– Effort applied at one end– Load is at the opposite end– Fulcrum is located between load & effort

(a) First-class lever

Arrangement of the elements isload-fulcrum-effort.

L

L

Example: scissors

Load

Fulcrum

Load Effort

Effort

Fulcrum

(a) First-class lever

Arrangement of the elements isload-fulcrum-effort.

In the body: A first-class lever systemraises your head off your chest. Theposterior neck muscles provide the effort;the atlanto-occipital joint is the fulcrum;and the weight to be lifted is the facialskeleton.

Load

Fulcrum

Effort

Lever Systems: Bone-Muscle Relationships

• Third-class lever– Effort is applied between the load & fulcrum– Work speedily– Always at a mechanical disadvantage

(c) Third-class lever

Arrangement of the elements isload-effort-fulcrum.

L

L

Example: tweezers or forceps

Fulcrum

Load

Load

Effort

Effort

Fulcrum

(c) Third-class lever

Arrangement of the elements isload-effort-fulcrum.

In the body: Flexing the forearm by thebiceps brachii muscle exemplifiesthird-class leverage. The effort is exertedon the proximal radius of the forearm; thefulcrum is the elbow joint; and the load isthe hand and distal end of the forearm.

Load

Effort

Fulcrum

Embryonic Development of the Muscles

• Muscles organized into 4 groups– Musculature of the visceral organs– Pharyngeal arch muscles– Axial muscles– Limb muscles

• Musculature of the visceral organs– Includes smooth & cardiac muscle– Develops from splanchnic mesoderm

• Pharyngeal arch muscles – Includes

• Skeletal muscles of the pharynx • Muscles of the head & neck

– Develop from the 4th to 7th somitomeres

Embryonic Development of the Muscles

Development of the Muscles

Limb bud

Myotomes

Limb bud

(a) 6-week embryo

Pharynx

Eye

First (occipital)myotomes

Somitomeres

(c) Pharyngeal arch (branchiomeric) muscles: 4th–7th somitomeres

Pharynx

Muscles of facial expressione.g., orbicularis oculi

Chewing musclese.g., temporalis, masseter

Suprahyoid muscles (most)

Pharyngeal constrictors(key swallowing muscles)

Trapezius

Pharyngeal Arch Muscles

Axial Muscles

• Lie anterior & posterior to the body axis

• Muscles of the: – Thorax, abdomen, & pelvis

• And many muscles of the:– Neck & some of the head

• Function to move the trunk & maintain posture

Deep muscles of the backe.g., erector spinae

Extrinsic musclesof the eye

Tonguemuscles

(d) Axial muscles: 1st–3rd somitomeres and myotomes

Tongue

Muscles of the anterior& lateral trunke.g., 1. infrahyoid muscles (neck) 2. intercostal muscles (thorax) 3. external & internal obliques (abdomen) 4. muscles of the pelvic floor

Axial Muscles

Limb Muscles

• Limb muscles arise from lateral parts of nearby myotomes

• Extensors– Muscle mass dorsal to limb bones

• Flexors– Muscle mass ventral to limb bones

Limb MusclesExtensorse.g., triceps brachii, extensor digitorum

Flexorse.g., biceps brachii, flexor carpi radialis

Extensorse.g., quadriceps femoris, tibialis anterior

Flexorse.g., hamstrings, gastrocnemius(e) Limb muscles: From myotomes

Extensors

Flexors

Muscle Actions & Interactions

• A muscle cannot reverse the movement it produces

• Another muscle must undo the action

• Muscles with opposite actions lie on opposite sides of a joint

Muscle Actions & Interactions

• Prime mover (= agonist)– Has major responsibility for a certain movement

• Antagonist– Opposes or reverses a movement

• Synergist helps the prime mover – By adding extra force – By reducing undesirable movements

Muscle Actions & Interactions

Example:Pectoralis major(anterior view)

(a) A muscle that crosses on the anterior side of a joint produces flexion*

*These generalities do not apply to the knee and ankle because the lower limb is rotated during development. The muscles that cross these joints posteriorly produce flexion, and those that cross anteriorly produce extension.

Example:Latissimus dorsi(posterior view)

(b) A muscle that crosses on the posterior side of a joint produces extension*

*These generalities do not apply to the knee and ankle because the lower limb is rotated during development. The muscles that cross these joints posteriorly produce flexion, and those that cross anteriorly produce extension.

Muscle Actions & Interactions

Example:Teres major(posterolateral view)

(d) A muscle that crosses on the medial side of a joint produces adduction

Example:Medial deltoid(anterolateral view)

(c) A muscle that crosses on the lateral side of a joint produces abduction

Muscle Compartments of the Limbs

• Dense fibrous connective tissue divides limb muscles into compartments

• Muscles in opposing compartments are– Agonist & antagonist pairs

• Each compartment is innervated by one single nerve

Muscle Compartments of Arm & Forearm

• The upper limb has anterior & posterior compartments– Anterior arm compartment muscles:

• Flex the shoulder or arm• Innervation is the musculocutaneous nerve

(we’ll learn later)

– Anterior forearm compartment muscles:• Flex the wrist & digits• Innervation is the median or ulnar nerve (..later)

Tricepsbrachii

Lateralhead

Humerus

Posterior compartmentof arm (extends elbow); innervation: radial nerve

Anterior compartment ofarm (flexes elbow); innervation:musculocutaneous nerve

LongheadMedialhead

(a)

Brachialis

Short headLong head

Biceps brachii

(a) Muscles of the arm

ExtensorsFlexors

Muscle Compartments of the Arm

Muscle Compartments of the Thigh

• Posterior compartment muscles – Extend the hip & flex the knee– Innervation is the tibial branch of the sciatic nerve (later)

• Anterior compartment muscles– Flex the hip & extend the knee– Innervation is the femoral nerve (later)

• Medial compartment– Adduct the thigh– Innervation is the obturator nerve (later)

Adductors

Vastuslateralis

Hamstrings

Posterior compartment ofthigh (flexes leg and extends thigh); innervation: tibial nerve (portion of sciatic nerve)

Medial compartment(adducts thigh); innervation:obturator nerve

Anterior compartment (extends leg); innervated by femoral nerve

Vastusintermedius

Rectus femoris

Femur

Vastus medialis

(a)

(a) Muscles of the thigh

Posterior compartmentmusclesAnterior compartmentmusclesMedial compartmentmuscles of thigh and lateral compartment muscles of leg

Muscle Compartments of the Thigh

Lab Guide for Learning the Muscles

Superficial Muscles of the Body

TrapeziusShoulder

DeltoidArmTriceps brachiiBiceps brachiiBrachialisForearmPronator teresBrachioradialisFlexor carpi radialisPalmaris longusPelvis/thighIliopsoasPectineusThighRectus femorisVastus lateralisVastus medialis

LegFibularis longusExtensor digitorumlongus Tibialis anterior

Head Facial

Temporalis Epicranius, frontal bellyOrbicularis oculiZygomaticusOrbicularis oris

NeckSternohyoidSternocleidomastoid

Thorax

Pectoralis major

Pectoralis minorSerratus anterior

IntercostalsAbdomen

External oblique

Rectus abdominisInternal obliqueTransversus abdominis

Thigh

Sartorius

Tensor fasciaelatae

Adductor longusGracilis

LegGastrocnemiusSoleus

Masseter

Platysma

Neck

Gracilis

Deltoid

ArmTriceps brachiiBrachialis

ForearmBrachioradialis

Extensor carpi ulnaris

Extensor digitorum

Iliotibial tract

LegGastrocnemiusSoleusFibularis longus

Epicranius, occipital bellySternocleidomastoid

Shoulder

HipGluteus mediusGluteus maximus

Thigh

Biceps femoris

Adductor magnus

SemitendinosusSemimembranosus

Hamstrings:

Latissimus dorsi

Rhomboid majorTriangle of auscultation

InfraspinatusTeres major

Flexor carpi ulnaris

Extensor carpi radialislongus

Calcaneal(Achilles) tendon

Trapezius

Superficial Muscles of the Body

Muscles of the Head – Facial Expression

• Muscles of facial expression– Lie in the face & scalp– Thin & variable in shape– Often insert in the skin not on bones– (Innervated by cranial nerve VII the facial

nerve)

Corrugator supercilii

Orbicularis oculiLevator labiisuperioris

Zygomaticusminor and major

BuccinatorRisoriusOrbicularis orisMentalisDepressorlabii inferioris

Depressor anguli oris

Platysma

Galeaaponeurotica

Frontalbelly

Occipitalbelly

Temporalis

Masseter

Sternocleidomastoid

Trapezius

Spleniuscapitis

Epicranius

Muscles of the Face & Head

Muscles of Mastication & Tongue Movement

• 4 main pairs of muscles involved in mastication– Innervated by mandibular division of the trigeminal

nerve (cranial nerve V)– Prime movers of jaw closure

• Masseter & temporalis

– Side-to-side movement• Pterygoid muscles

– Compression of cheeks• Buccinator muscles

PLAYPLAY A&P Flix: Buccinator PLAYPLAY A&P Flix: Masseter PLAYPLAY A&P Flix: Temporalis

Muscles of Mastication & Tongue Movement

Orbicularisoris

Temporalis

Masseter

Buccinator

(a)

Lateralpterygoid

Medialpterygoid

Masseterpulled away

(b)

Muscles of the Anterior Neck & Throat – Swallowing

• The neck is divided into anterior & posterior triangles

• Anterior triangle – Divided into suprahyoid & infrahyoid muscles– Participate in swallowing

• Pharyngeal constrictors– Swallowing muscles squeeze food into

esophagus

Muscles of the Anterior Neck & Throat

Buccinator

Tensor veli palatini

Levator veli palatini

Superior pharyngealconstrictor

Middle pharyngealconstrictor

Hyoid boneThyrohyoidmembrane

Inferiorpharyngealconstrictor

Esophagus

Mandible

Mylohyoid(cut)

Geniohyoid

Hyoglossus

Thyroidcartilageof larynx

Trachea

Styloid process

Muscles of the Neck & Vertebral Column

• Head movement:– Sternocleidomastoid – Splenius muscles – Neck movement – scalenes

1st cervicalvertebra

Sternocleido-mastoid

Base ofoccipitalbone

Middlescalene

Anteriorscalene

Posteriorscalene

(a) Anterior

Mastoidprocess

Splenius capitis

Mastoid process

Spinous processesof the vertebrae

Splenius cervicis

(b) Posterior

Muscles of the Neck & Vertebral Column

Muscles of the Neck & Vertebral Column

• Trunk extension – Deep muscles of the back

• Maintain normal curvatures of the spine• Form a column from sacrum to the skull

– Erector spinae group• Largest of the deep back muscles

Mastoid processof temporal bone

Semispinaliscapitis

Semispinaliscervicis

Multifidus

Quadratuslumborum

Semispinalisthoracis

Longissimus capitis

Iliocostalis cervicis

Longissimus cervicis

Iliocostalis thoracisLongissimus thoracisSpinalis thoracis

Iliocostalis lumborum

External oblique

IliocostalisLongissimusErector spinaeSpinalis

Ligamentumnuchae

Muscles of the Neck & Vertebral Column

PLAYPLAY A&P Flix: Iliocostalis

PLAYPLAY A&P Flix: Longissimus

PLAYPLAY A&P Flix: Spinalis

Deep Muscles of the Thorax –Breathing

• Deep muscles provide movements for breathing – External intercostal muscles

• Lift the rib cage during inhalation

– Internal intercostal muscles • Aid expiration during heavy breathing

Deep Muscles of the Thorax—Breathing

Externalintercostal

Internalintercostal

PLAYPLAY A&P Flix: External intercostal muscles PLAYPLAY A&P Flix: Internal intercostal muscles

Deep Muscles of the Thorax –Breathing

• Diaphragm– Most important muscle of respiration!– Flattens as it contracts

• Increases the volume of the thoracic cavity• How does this aid in breathing?• Innervated by phrenic nerve (your brain controls)

Foramen foresophagus

Costal cartilage

Lumbarvertebra

Diaphragm

Quadratuslumborum

Psoas major

Xiphoid process of sternum

Foramen for inferiorvena cava

Centraltendon ofdiaphragm

Foramenfor aorta

12th rib

Deep Muscles of the Thorax—Breathing

Muscles of the Abdominal Wall

• Lateral & anterior abdominal wall– Formed from 3 flat muscle sheets

• External oblique• Internal oblique • Transversus abdominis

– Fourth muscle pair• Rectus abdominis

– Inserts at the linea alba

Serratusanterior

Pectoralis major

Linea alba

Tendinousintersection

Rectusabdominis

Inguinal ligament(formed by free inferior border of the external oblique aponeurosis)

Transversusabdominis

Internal oblique

Externaloblique

Aponeurosisof the externaloblique

(a)

Muscles of the Abdominal Wall

PLAYPLAY A&P Flix: Internal obliques PLAYPLAY A&P Flix: External obliques

PLAYPLAY A&P Flix: Transverse abdominis PLAYPLAY A&P Flix: Rectus abdominis

Rectusabdominis

Internal oblique

Externaloblique

Transversusabdominis

Muscles of the Abdominal Wall

Muscles of the Pelvic Floor

• Pelvic floor (pelvic diaphragm)

• Sheet of 2 muscles– Both support pelvic organs

• Levator ani– Formed from iliococcygeus, puborectalis, &

pubococcygeus

• Coccygeus

Muscles of the Pelvic Floor

Pelvicdiaphragm

Symphysis pubis

Levator aniPiriformis

Posterior

Anterior

Coccyx

Coccygeus

Obturatorinternus

IIiococcygeusLevator ani

Pubococcygeus

Urogenital diaphragm

UrethraVaginaAnal canal

Muscles of the Perineum

Male Female

Penis

Midline raphe

Ischiocavernosus

Clitoris

Urethralopening

Anus

Vaginalopening

Bulbospongiosus

Superficialtransverseperineal muscle

Levator ani

Gluteusmaximus

Superficial Muscles of the Anterior Thorax

• Movements of the scapula– Pectoralis major– Pectoralis minor– Serratus anterior– Subclavius

PLAYPLAY A&P Flix: Pectoralis major

PLAYPLAY A&P Flix: Pectoralis minor

PLAYPLAY A&P Flix: Serratus anterior

Superficial Muscles of Anterior Thorax

Sternocleidomastoid

Deltoid

Pectoralismajor

Sternum

Bicepsbrachii

Subclavius

Clavicle

Subscapularis

Pectoralisminor

Coracobrachialis

Serratusanterior

Humerus

Superficial Muscles of the Posterior Thorax

• Movements of the scapula– Trapezius– Levator scapulae– Rhomboid major– Rhomboid minor

PLAYPLAY A&P Flix: Trapezius PLAYPLAY A&P Flix: Levator scapulae

PLAYPLAY A&P Flix: Rhomboid major PLAYPLAY A&P Flix: Rhomboid minor

Trapezius

Levatorscapulae

Supraspinatus

Clavicle

Spine of scapula

Infraspinatus

Teres minor

Humerus

Deltoid

Teresmajor

Latissimusdorsi

Rhomboidminor

Rhomboidmajor

Superficial Muscles of the Posterior Thorax

Muscles Crossing the Shoulder Joint

• Movements of the arm– Deltoid– Pectoralis major

Clavicle

Deltoid

Sternum

Pectoralis major

Lateral headLong head

Medial head

Coracobrachialis

Triceps brachii

Biceps brachii

Brachialis

Brachio-radialis

(a) Anterior view

PLAYPLAY A&P Flix: Deltoid

• Movements of the arm

A&P Flix: Latissimus dorsi

A&P Flix: Supraspinatus

A&P Flix: Infraspinatus

Supraspinatus

Spine of scapula

(b) Posterior view

Deltoid (cut)

Greater tubercleof humerusInfraspinatus

Teres minor

Teres major

Triceps brachii

Latissimus dorsi

Humerus

Olecranon processof ulna

Lateral head Long head

Anconeus

PLAYPLAY

PLAYPLAY

PLAYPLAY

Muscles Crossing the Shoulder Joint

• Movements of arm

A&P Flix: Teres minor

A&P Flix: Teres major

A&P Flix: Subscapularis

Supraspinatus

Spine of scapula

(b) Posterior view

Deltoid (cut)

Greater tubercleof humerusInfraspinatus

Teres minor

Teres major

Triceps brachii

Latissimus dorsi

Humerus

Olecranon processof ulna

Lateral head Long head

Anconeus

PLAYPLAY

PLAYPLAY

PLAYPLAY

Muscles Crossing the Shoulder Joint

Questions…?

What’s Next?Lab: MusclesNext Lecture: Muscles cont… Wed Lab: Finish Muscles & Review