Ch 11 01 Lecture Presentation (1)

© 2014 Pearson Education, Inc.

PowerPoint® Lecture Presentations prepared byLeslie Hendon

University of Alabama, Birmingham

11 PART 1

Muscles of the Body


Muscles of the Body

• Skeletal muscles

• Produce movements

• Blinking the eye, standing on tiptoe, swallowing food, etc.

• General principles of leverage

• Muscles act with or against each other

• Criteria used in naming muscles


Arrangement of Fascicles in Muscles

• Skeletal muscles—consist of fascicles

• Fascicles—arranged in different patterns

• Fascicle arrangement—tells about action of a muscle



• Types of fascicle arrangement

• Convergent

• Origin of the muscle is broad

• Fascicles converge toward the tendon of insertion

• Example—pectoralis major




• Parallel—fascicles run parallel to the long axis of the muscle

• Straplike—sternocleidomastoid

• Fusiform—biceps brachii




• 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



• Circular

• Fascicles are arranged in concentric rings

• Surround external body openings

• Sphincter—general name for a circular muscle

• Examples

• Orbicularis oris and orbicularis oculi


Figure 11.1 Patterns of fascicle arrangement in muscles.

Fusiform(biceps brachii)

Parallel(sartorius)

Convergent(pectoralis major)

Circular(orbicularis oris)

Multipennate(deltoid)

Unipennate(extensor digitorumlongus)

Bipennate(rectus femoris)

(a)

(b)(c)

(d)

(e)

(f)

(g)


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


Figure 11.2a Lever systems operating at a mechanical advantage and a mechanical disadvantage.

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

Mechanical advantage with a power lever

Effort

Effort

1000 kg

Load

LoadFulcrum

Fulcrum

0.25 cm

25 cm

10kg

10 25 1000 0.25 250 250


Figure 11.2b Lever systems operating at a mechanical advantage and a mechanical disadvantage.

Mechanical disadvantage with a speed lever

Effort

Effort

50 kg

Load

Load

Fulcrum Fulcrum

25 cm

50 cm

100 kg

100 25 50 50 2500 2500

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



• Levers allow a given effort to

• Move a heavier load

• Move a load farther

• Mechanical advantage

• Moves a large load over small distances

• Mechanical disadvantage

• Allows a load to be moved over a large distance



• Bones—act as levers

• Joints—act as fulcrums

• Muscle contraction

• Provides effort–applied where muscle attaches to bone

• Load

• Bone, overlying tissue, and anything lifted



• First-class lever

• Effort applied at one end

• Load is at the opposite end

• Fulcrum is located between load and effort

• Examples—seesaws, scissors, and lifting your head off your chest


Figure 11.3a Lever systems.First-class lever

Effort

L

Load

Fulcrum

Arrangement of the elements isload-fulcrum-effort.

Effort

L

Load

Fulcrum

Example: scissors

EffortLoad

Fulcrum

In the body: A first-class lever system raises yourhead off your chest. The posterior neck musclesprovide the effort; the atlanto-occipital joint is thefulcrum; and the weight to be lifted is the facialskeleton.



• Second-class lever

• Effort applied at one end

• Fulcrum is at the opposite end

• Load is between the effort and fulcrum

• Examples—wheelbarrow or standing on tiptoe

• An uncommon type of lever in the body

• Works at a mechanical advantage


Figure 11.3b Lever systems.Second-class lever

Effort

L

Load

Fulcrum

Arrangement of the elements isfulcrum-load-effort.

Effort

L

Load

Fulcrum

Example: wheelbarrow

Effort

Load

Fulcrum

In the body: Second-class leverage is exerted whenyou stand on tip-toe. The effort is exerted by the calfmuscles pulling upward on the heel; the joints of theball of the foot are the fulcrum; and the weight of thebody is the load.



• Third-class lever

• Effort is applied between the load and the fulcrum

• Works speedily

• Always at a mechanical disadvantage


Figure 11.3c Lever systems.Third-class lever

Effort

L

Load

Fulcrum

Arrangement of the elements isload-effort-fulcrum.

Effort

L

Load

Fulcrum

Example: tweezers or forceps

Effort

Load

Fulcrum

In the body: Flexing the forearm by the bicepsbrachii muscle exemplifies third-class leverage. Theeffort is exerted on the proximal radius of the forearm;the fulcrum is the elbow joint; and the load is the hand and distal end of the forearm.



• Most skeletal muscles are third-class levers

• Example—biceps brachii

• Fulcrum—the elbow joint

• Force—exerted on the proximal region of the radius

• Load—the distal part of the forearm


Organization Scheme Based on Embryonic Development• Groups of muscles organized by

• Embryonic origin

• General function

• Muscles develop from mesoderm

• Myotomes

• Somitomeres

• The first seven myotomes of the head

• Splanchnic mesoderm


Figure 11.4a Development and basic organization of the muscles.

Limb bud

Myotomes

6-week embryo

Limb bud

Pharynx

Eye

Somitomeres

First (occipital)myotomes


Figure 11.4b Development and basic organization of the muscles.

Cross section at level oflower limb buds

Limb bud

Vertebra

Splanchnicmesoderm

Limb skeleton

Dorsal

Gut tube Limb flexion

Limb extension

Flexormusclesof limbs

Neuraltube

Extensormusclesof limbs

Myotome

Somaticmesoderm


Organization Scheme Based on Embryonic Development• Muscles organized into four groups

• Musculature of the visceral organs

• Pharyngeal arch muscles

• Axial muscles

• Limb muscles


Organization Scheme Based on Embryonic Development• Muscle of the visceral organs

• Includes smooth and cardiac muscle

• Develops from splanchnic mesoderm

• Pharyngeal arch muscles

• Includes

• Skeletal muscles of the pharynx

• Muscles of the head and neck

• Develop from the fourth to seventh somitomeres


Figure 11.4c Development and basic organization of the muscles.

Pharynx

Trapezius

Muscles of facial expressione.g., orbicularis oculi

Chewing musclese.g., temporalis, masseter

Suprahyoid muscles (most)

Pharyngeal constrictors(key swallowing muscles)

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


Axial Muscles

• Lie anterior and posterior to the body axis

• Muscles of the

• Thorax, abdomen, and pelvis

• Many muscles of the neck

• Some muscles of the head

• Function to move the trunk and maintain posture


Axial Muscles

• Develop from myotomes and some somitomeres

• Dorsal regions of myotomes—deep muscles of the back

• Ventral regions of myotomes—muscles of the trunk and neck

• Respiratory muscles

• Anterior abdominal wall muscles

• Muscles of the pelvic floor


Figure 11.4d Development and basic organization of the muscles.

Deep muscles of the backe.g., erector spinae

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

Axial muscles: 1st–3rd somitomeres and from myotomes

Extrinsic musclesof the eye

Tongue Tonguemuscles


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 Muscles

• Upper limb

• Extensors on posterior side

• Flexor muscles on anterior side

• Lower limb

• Rotates in embryonic development

• Extensors on anterior side

• Flexor muscles on posterior side


Figure 11.4e Development and basic organization of the muscles.

Limb muscles:From myotomes

Extensors

Flexorse.g., hamstrings,gastrocnemius

Extensorse.g., quadricepsfemoris, tibialisanterior

Flexorse.g., biceps brachii,flexor carpi radialis

Extensorse.g., triceps brachii,extensor digitorum

Flexors


Muscle Actions and 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 and 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

• Fixator

• A type of synergist that holds a bone firmly in place


Figure 11.5 The action of a muscle can be inferred by the position of the muscle relative to the joint it crosses.


Muscle Compartments of the Limbs

• Dense fibrous connective tissue divides limb muscles into compartments

• Muscles in the same compartment

• Have similar actions; act as synergists

• Muscles in opposing compartments are

• Agonist and antagonist pairs

• Each compartment is innervated by a single nerve


Muscle Compartments the Upper Limb

• The upper limb has anterior and posterior compartments

• Anterior arm compartment muscles

• Flex the shoulder or arm

• Innervation is the musculocutaneous nerve

• Anterior forearm compartment muscles

• Flex the wrist and digits

• Innervation is the median or ulnar nerve


Figure 11.6a Superficial muscles of the body.

Facial

Forearm

Arm

Shoulder

Head

Deltoid

Zygomaticus

Epicranius, frontal belly

Orbicularis oculi

Orbicularis oris

Temporalis

Masseter

Trapezius

Triceps brachiiBiceps brachiiBrachialis

Pronator teres

Palmaris longus

BrachioradialisFlexor carpi radialis

Thigh

Leg

Pelvis/thigh

Tibialis anterior

Iliopsoas

Pectineus

Rectus femoris

Vastus medialis

Fibularis longus

Extensor digitorum longus

Vastus lateralis

Neck

SternohyoidPlatysma

AbdomenRectus abdominis

External oblique

ThoraxSternocleidomastoid

Pectoralis minor

Pectoralis majorSerratus anteriorIntercostals

Internal oblique

Transversus abdominis

ThighTensor fasciae latae

Leg

Sartorius

Adductor longus

Gracilis

Gastrocnemius

Soleus


Forearm

Arm

Shoulder

Hip

DeltoidRhomboid minor

Splenius capitis

Levator scapulae

Epicranius, occipital belly

InfraspinatusTeres major

Trapezius

Triceps brachii

Biceps femoris

Brachialis

Extensor digitorum

Brachioradialis

Flexor carpi ulnaris

Iliotibial tract

Fibularis longus

Calcaneal(Achilles) tendon

Neck

Semitendinosus

Sternocleidomastoid

Latissimus dorsi

Rhomboid majorTriangle of auscultation

Gluteus medius

Thigh

Leg

Hamstrings:

Adductor magnusGracilis

Gastrocnemius

Soleus

Extensor carpi ulnaris

Extensor carpi radialislongus

Splenius cervicis

Rhomboid major

Gluteus maximus

Semimembranosus

Figure 11.6b Superficial muscles of the body, continued.


Muscle Compartments of the Thigh

• Posterior compartment muscles

• Extend the hip and flex the knee

• Innervation is the tibial branch of the sciatic nerve

• Anterior compartment muscles

• Flex the hip and extend the knee

• Innervation is the femoral nerve

• Medial compartment

• Adduct the thigh

• Innervation is the obturator nerve


Figure 11.7a Muscle compartments in the arm and forearm.

Muscles of the arm

Tricepsbrachii

BrachialisExtensors

Lateral head

Flexors

Long head

Medial head

Posterior compartment of arm(extends forearm at elbow);innervation: radial nerve

Humerus

Biceps brachiiShort headLong head

(a)

Anterior compartment of arm(flexes forearm at elbow);innervation: musculocutaneous nerve


Muscle Compartments of the Leg

• Posterior compartment muscles

• Contains digital and plantar flexors

• Innervation is the tibial nerve

• Anterior compartment muscles

• Contains digital extensors and dorsiflexors

• Innervation is the deep fibular nerve

• Lateral compartment muscles

• Plantar flex and evert the foot

• Innervation is the superficial fibular nerve


Figure 11.7b Muscle compartments in the arm and forearm.

Extensors

Pronator teres

Extensors

Abductor pollicislongus

Flexors

Posterior compartment of forearm(extends wrist and fingers);innervation: radial nerve

Radius

Brachioradialis(elbow flexor)

Muscles of the forearm

Flexors

Ulna

Anterior compartment of forearm (flexes wrist and fingers);innervation: median or ulnar nerve

(b)


Naming the Skeletal Muscles

• Location

• Example—the brachialis is located on the arm

• Shape

• Example—the deltoid is triangular

• Relative size

• Maximus, minimus, and longus indicate size

• Example—gluteus maximus and gluteus minimus



• Direction of fascicles and muscle fibers

• Name tells direction in which fibers run

• Example—rectus abdominis and transversus abdominis

• Location of attachments—name reveals point of origin and insertion

• Example—brachioradialis



• Number of origins

• Two, three, or four origins

• Indicated by the words biceps, triceps, and quadriceps

• Action

• The action is part of the muscle’s name

• Indicates type of muscle movement

• Flexor, extensor, adductor, or abductor

Ch 11 01 Lecture Presentation (1)

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