Muscles of the Body Muscles of the Body I. Movement and Leverage - - PowerPoint PPT Presentation

Muscles of the Body

Muscles of the Body

I. Movement and Leverage Systems II. Muscles action III. Fascicle Arrangement IV. Criteria used in naming muscles V. The Muscles (Lab)

2

• I. Movement & Leverage Systems

A. What is and Why use levers?

1. What it is:

a. Physics definition: a rigid bar that pivots about one point and is used to move an object at a second point by a force applied at a third. b. Altered for anatomy: rigid bars (bones) that pivot about a point (joint) and is used to move an object at a second point by a force applied (muscles) at a different point (this point depends on the lever classification).

2. Why use:

a. to gain a mechanical advantage as it relates to movement

• f the body… usually in speed and strength

3

• I. Movement & Leverage Systems

B. Leverage components

1. Leverage systems require at least three components

a. Lever – a rigid bar that moves (bones) b. Fulcrum – a fixed point (joint) c. Effort – applied force (muscles) d. Load – resistance (weight/mass)

C. Classification of levers

1. First Class 2. Second Class 3. Third Class

4

Lever Systems – Mechanical Advantage Example

5

• I. Movement & Leverage Systems
• C. Classification of Lever Systems
• 1. First‐class lever
• Effort applied at one end
• Load is at the opposite end
• Fulcrum is located between load and effort
• Example?

6

• I. Movement & Leverage Systems
• C. Classification of Lever Systems
• 1. Second‐class lever
• Effort applied at one end
• Fulcrum is at the opposite end
• Load is between the effort and

fulcrum

• An uncommon type of lever in the

body

• Work at a mechanical advantage
• Example?

7

• I. Movement & Leverage Systems
• C. Classification of Lever Systems
• 3. Third‐class lever
• Effort is applied between the load and the

fulcrum

• Work speedily
• Always at a mechanical disadvantage (why?)
• Example?

8

II. Muscle Actions

• A. General Principles of Muscle Action
• 1. A muscle cannot reverse the movement it

produces

• a. Remember: muscle tissue when active ONLY

shortens!

• 2. Another muscle must undo the action
• 3. Muscles with opposite actions typically lie on
• pposite sides of a joint (if not, the force is

directed to the opposite side via tendon).

9

II. Muscle Action

A. Muscle Action Terms:

1. Prime mover (agonist)

• has major responsibility for a certain movement
• Example:

2. Antagonist

• pposes or reverses a movement
• Example:

3. Synergist

• helps the prime mover by:

– By adding extra force – By reducing undesirable movements

• Example:

4. Fixator

• a type of synergist that holds a bone firmly in place
• Example:

10

III. Arrangement of Fascicles

• A. General Info to remember:
• 1. Skeletal muscles – consist of fascicles
• 2. Fascicles – arranged in different patterns
• 3. Fascicle arrangement – tells about action
• f a muscle

11

III. Arrangement of Fascicles

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

axis of the muscle

• a. Strap‐like – sternocleidomastoid
• b. Fusiform – biceps brachii
• 2. Convergent
• a. Origin of the muscle is broad
• b. Fascicles converge toward the tendon of

insertion c. Example – pectoralis major

12

III. Arrangement of Fascicles

B. Types of fascicle arrangement cont…

3. Pennate

a. Unipennate – fascicles insert into one side of the tendon b. Bipennate – fascicles insert into the tendon from both sides c. Multipennate – fascicles insert into one large tendon from all sides

4. Circular – fascicles are arranged in concentric rings

a. Surround external body openings b. Sphincter – general name for a circular muscle c. Examples – orbicularis oris and orbicularis oculi

13

III. Arrangement of Fascicles

14

IV. Naming the Skeletal Muscles

A. Location

– Example – the brachialis is located on the arm

B. Shape

– Example – the deltoid is triangular

C. Relative size

– Maximus, minimus, and longus indicate size – Example – gluteus maximus and gluteus minimus

15

IV. Naming the Skeletal Muscles

• D. Direction of fascicles and muscle fibers

– Name tells direction in which fibers run – Example – rectus abdominis or circularis

• culi
• E. Location of attachments – name reveals

point of origin and insertion

– Example – brachioradialis or sternocleidomastoid

16

IV. Naming the Skeletal Muscles

• F. Number of origins – two, three, or four
• rigins

– Indicated by the words biceps, triceps, and quadriceps

• G. Action – the action is part of the muscle’s

name

– Indicates type of muscle movement

• Flexor, extensor, adductor, or abductor

17

• V. Muscles

18

Superficial Muscles of the Body –

Anterior View

19

Superficial Muscles of the Body –

Posterior View

20

Muscles of the Head

Facial Expression

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

nerve

21

Muscles of the Head

Facial Expression

22

Muscles of the Head – Mastication and Tongue Movement

• Four main pairs of muscles involved in

mastication

– Innervated by mandibular division – the trigeminal nerve – Prime movers of jaw closure – masseter and temporalis – Side‐to‐side movement – pterygoid muscles – Compression of cheeks – buccinator muscles

23

Muscles of the Head

Mastication and Tongue Movement

24

Muscles of the Head

Mastication and Tongue Movement

• Extrinsic muscles of the tongue
• Move tongue:

– Laterally – Anteriorly – Posteriorly

• All innervated by cranial nerve XII – the

hypoglossal nerve

25

Muscles of the Head

Mastication and Tongue Movement

26

Muscles of the Anterior Neck and Throat

Swallowing

• The neck is divided into anterior and posterior

triangles

• Anterior triangle

– Divided into suprahyoid and infrahyoid muscles – Participate in swallowing

• Pharyngeal constrictors – squeeze food into

the esophagus

27

Muscles of the Anterior Neck and Throat

Swallowing

28

Muscles of the Anterior Neck and Throat

Swallowing

29

Muscles of the Neck and Vertebral Column

• Head movement

– Sternocleidomastoid – Splenius capitis and splenius cervicis

30

Muscles of the Neck and 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

31

Muscles of the Neck and Vertebral Column

32

Deep Muscles of the Thorax – Breathing

• Deep muscles provide movements for breathing

– External intercostal muscles

• Lift the ribcage

– Internal intercostal muscles

• May aid expiration during heavy breathing
• Diaphragm – most important muscle of respiration

– Flattens as it contracts – increases the volume of the thoracic cavity

33

Deep Muscles of the Thorax – Breathing

34

Figure 11.10a

Deep Muscles of the Thorax – Breathing

35

Muscles of the Abdominal Wall

• Lateral and anterior abdominal wall

– Formed from three flat muscle sheets

• External oblique
• Internal oblique
• Transversus abdominis

– Fourth muscle pair

• Rectus abdominis – inserts at linea alba

36

Muscles of the Abdominal Wall

37

Muscles of the Pelvic Floor

• Pelvic floor (pelvic diaphragm)
• Sheet of two muscles – both support pelvic
• rgans

– Levator ani – formed from iliococcygeus, puborectalis, and pubococcygeus – Coccygeus

38

Muscles of the Pelvic Floor

39

Muscles of the Perineum

• Inferior to the muscles of the pelvic floor
• Urogenital diaphragm formed from:

– Sphincter urethrae and the deep transverse perineus

40

Figure 11.12b

Muscles of the Perineum

• Muscles of the superficial perineal space

– Ischiocavernosus – Bulbospongiosus – Superficial transverse perineus

41

Superficial Muscles of the Anterior Thorax

• Movements of

the scapula

– Pectoralis major – Pectoralis minor – Serratus anterior – Subclavius

42

Superficial Muscles of the Posterior Thorax

• Movements of the scapula

– Trapezius – Levator scapulae – Rhomboid major – Rhomboid minor

43

Muscles Crossing the Shoulder Joint

• Movements of the arm

– Deltoid – Pectoralis major

44

Muscles Crossing the Shoulder Joint

• Movements of the arm

– Latissimus dorsi – Supraspinatus – Infraspinatus – Teres minor – Teres major – Coracobrachialis – Subscapularis

45

Muscles Crossing the Elbow Joint

• Posterior muscles –

extensors of the forearm

– Triceps brachii – Anconeus

• Anterior muscles –

flexors of the forearm

– Biceps brachii – also supinates the forearm – Brachialis – Brachioradialis

46

Muscles of the Forearm

• Movements of the wrist, hand, and fingers

– Tendons are anchored by

• Flexor and extensor retinacula

– Most forearm muscles arise from the distal humerus – Movements at the wrist include:

• Flexion, extension, abduction, and adduction

– Wrist and fingers are “operated” by muscles in the forearm

47

Muscles of the Forearm

• Flexors – anterior flexor compartment

– Innervated by median and ulnar nerves

• Originate from a common tendon

– Medial epicondyle of the humerus

48

Superficial Anterior Muscles of the Forearm

• Pronator teres
• Flexor carpi radialis
• Palmaris longus
• Flexor carpi ulnaris
• Flexor digitorum

superficialis

49

Deep Anterior Muscles of the Forearm

• Flexor pollicis

longus

• Flexor digitorum

profundus

• Pronator

quadratus

50

Muscles of the Forearm

• Extensors – posterior compartment

– Innervated by the radial nerve – Originate at a common tendon

• Lateral epicondyle of the humerus

51

Superficial Posterior Muscles of the Forearm

• Brachioradialis –

flexes forearm

• Extensor carpi

radialis longus

• Extensor carpi

radialis brevis

• Extensor digitorum
• Extensor carpi ulnaris

52

Deep Posterior Muscles of the Forearm

• Supinator –

supinates forearm

• Abductor pollicis

longus

• Extensor pollicis

brevis and longus

• Extensor indicus

53

Summary of Actions of the Muscles

• f the Arm and Forearm

54

Summary of Actions of the Muscles

• f the Arm and Forearm

55

Intrinsic Muscles of the Hand

• Fine movement of the fingers
• All located in the palm
• Control precise movements
• Include muscles of:

– Adduction, abduction, and opposition

56

Intrinsic Muscles of the Hand

• Thenar muscles – ball of thumb

– Abductor pollicis brevis – Flexor pollicis brevis – Opponens pollicis – Adductor pollicis

• Hypothenar muscles

– Abductor digiti minimi – Flexor digiti minimi – Opponens pollicis

57

Intrinsic Muscles of the Hand

58

Intrinsic Muscles of the Hand

• Midpalmar muscles

– Lumbricals – Palmar interossei – Dorsal interossei

59

Intrinsic Muscles of the Hand

60

Figure 11.18c

Muscles Crossing the Hip and Knee Joints

Thigh and leg movements

• Anterior muscles

– Flex the thigh and extend the leg at the knee

• Posterior muscles

– Extend the thigh and flex the leg

• Adductor muscles – on medial aspect of thigh

– Adduct the thigh only

• Deep fascia of the thigh

– Surrounds and encloses all three groups

61

Muscles Crossing the Hip and Knee Joints

Movements at the hip joint

• Muscles that flex the thigh

– Originate on vertebral column or pelvis

• Muscles that extend the thigh

– Arise posterior to the hip joint

• Adductors originate medial to the hip joint
• Abductors originate lateral to the hip joint

62

Anterior and Medial Muscles

• Origin on pelvis or

vertebral column

– Iliacus – Psoas major – Sartorius

• Muscles of the medial

compartment

– Adductor longus – Adductor brevis – Adductor magnus – Pectineus – Gracilis

63

Muscles of the Anterior Compartment of the Thigh

• Quadriceps femoris –

four separate heads

– Have a common insertion at the quadriceps tendon – Powerful knee extensors

• Rectus femoris
• Vastus lateralis
• Vastus medialis
• Vastus intermedius

– Tensor fasciae latae

64

Posterior Muscles

• Origin on pelvis or sacrum

– Gluteus maximus – Gluteus medius – Gluteus minimus

• Lateral rotators

– Piriformis – Obturator externus – Obturator internus – Superior and inferior gemellus – Quadratus femoris

65

Muscles of the Posterior Compartment of the Thigh

• Hamstrings
• Biceps femoris
• Semitendinosus
• Semimembranosus

66

Muscles of the Leg

• Fascia lata of the leg surrounds muscles

– Tightly binds muscles – Prevents swelling during exercise – Aids venous return – Divides leg into three compartments

• Tendons are held in place by:

– Extensor, fibular, and flexor retinacula

• Muscle movement at ankle and intertarsal

joints

67

Muscles of the Anterior Compartment

• Tibialis anterior
• Extensor digitorum

longus

• Fibularis (peroneus)

tertius

• Extensor hallucis

longus

68

Muscles of the Lateral Compartment

• Fibularis (peroneus)

longus

• Fibularis (peroneus)

brevis

69

Muscles of the Lateral Compartment

70

Muscles of the Posterior Compartment

• Superficial

muscles

– Triceps surae

• Gastrocnemius
• Soleus

– Plantaris

71

Muscles of the Posterior Compartment

• Deep muscles

– Popliteus – Flexor digitorum longus – Flexor hallucis longus – Tibialis posterior

72

Summary of Actions of Muscles of the Thigh and Leg

73

Summary of Actions of Muscles of the Thigh and Leg

74

Intrinsic Muscles of the Foot

• Toe movement and foot support

– Help to flex, extend, abduct, and adduct the toes – Support the arches of the foot – Single muscle on dorsal aspect of the foot – Many muscles on the plantar aspect

75

Intrinsic Muscles of the Foot

• Muscle on the dorsum of

the foot

– Extensor digitorum brevis

• Muscles on the sole of

the foot

– First layer

• Flexor digitorum brevis
• Abductor hallucis
• Abductor digiti minimi

76

Figure 11.25a

Intrinsic Muscles of the Foot

• Second layer

– Flexor accessorius – Lumbricals

77

Figure 11.25b

Intrinsic Muscles of the Foot

• Third layer

– Flexor hallucis brevis – Adductor hallucis – Flexor digiti minimi brevis

• Fourth layer

– Plantar and dorsal interossei

78

Intrinsic Muscles of the Foot

79

Lever Systems – Mechanical Advantage Example

80