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Muscles of the Body Chapter 11.

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1 Muscles of the Body Chapter 11

2 Interactions of Skeletal Muscles
The arrangement of body muscles permits them to work either together or in opposition to achieve a movement As muscle contract they can only pull on the skeleton; they can never push If you are pushing an object it is the contraction of some group of muscles in the body that will accomplish it Generally muscles are grouped to “undo” an action done by another group Quadriceps / Hamstrings

3 Working out with Muscles
Muscle contraction causes shortening, not lengthening of a muscle Concentric / shortening against resistance Eccentric / lengthening against resistance Typically as a muscle contracts it moves its insertion toward its origin Lat. bar pull down / Latissimus dorsi However, some muscles can contract and move its origin toward its insertion Pull ups / Latissiums dorsi

4 Functional Muscle Groups
Muscles can be classified into four functional groups Prime movers Antagonists Synergists Fixators

5 Prime Movers A muscle that provides the major force for producing a specific movement is called a prime mover or agonist The biceps brachii is the prime mover of elbow flexion Origin of Biceps Brachii Coracoid Process

6 Antagonist Muscles that oppose a particular movement are called antagonist When a prime mover is active, the antagonist muscles are often stretched and may be in a relaxed state Antagonists also regulate the action of prime mover

7 Synergist Synergists aid agonists by promoting the same movement and by reducing extraneous movements that may be produced when the prime mover acts In two joint muscles synergists stabilize a joint as the muscle acts on the other Synergist can also restrict rotary movement at a joint so the muscle’s full effort be applied to the desired movement

8 Fixator When a synergist immobilize a muscle’s origin they are called fixators Their action serves to stabilize the bone upon which a prime mover acts Serratus anterior holds the scapula against the thorax while a prime mover acts upon the arm

9 Naming Skeletal Muscles
Location of the muscle Intercostal, Temporalis Shape of the muscle Deltoid; Trapezius Relative size of the muscle Maximus; medius; minimus; brevis; longus Direction of muscle fibers Rectus (straight) fibers run parallel to line of pull Transverse; fibers run perpendicular to line Oblique; fibers are oblique to the line

10 Naming of Muscles Number of origins
Biceps; triceps; quadriceps Location of muscle origin and/or insertion Sterno (sternum); cleido (clavicle); mastoid (mastoid process of temporal bone) Action of the muscle Flexor; extensor; adductor, supinator

11 Arrangement of Fascicles
Arrangement of fascicles within a muscle vary Arrangements result in differing shapes and capabilities Common forms are Parallel fusiform Pennate Uni-, bi-, multi- Convergent Circular or sphincteral


13 Parallel Arrangement of Fascicles
In parallel arrange- ment the long axis of the fascicles run parallel to the long axis of the muscle Form long straplike muscles that have greatest potential for shortening Act over a long excursion Not very powerful

14 Pennate Arrangement of Fascicles
Pennate fascicles are short and they attach obliquely to a central tendon Occur as pennate, bipennate and multipennate forms Pennate muscles with the highest concentration of fibers, shorten little, but are very powerful A) Pennate / Ext. digitorum longus B) Bipennate / Rectus Femoris C) Multipennate / Deltoid

15 Convergent Arrangement of Fascicle
A convergent muscle has a broad origin and its fascicles converge toward a single tendon Muscle has a broad triangular shape Muscle can act upon the joint from a variety of positions Pectoralis major

16 Circular Arrangement of Fascicles
Fascicular pattern is arranged in concentric rings Muscles with this arrangement surround external body openings which they close by contracting This type of muscles are called sphincters which literally means squeezers

17 Lever Systems The operation of most skeletal muscles involves the use of levers and lever systems Lever A rigid bar that moves on a fixed point Fulcrum A fixed point of leverage Effort The forced applied to move a resistance Load The resistance to me moved

18 Lever Systems In the human body . . . Levers Fulcrums Effort Load
The bones of the skeleton Fulcrums The joints of the body Effort Applied by the muscles of the body Load Bone, overlying tissue, and other objects to which your body applies force

19 Lever Systems A lever allows a given effort to move a heavier load or to move a load farther or faster that it otherwise could A small difference in the site of a muscle’s insertion can translate into large differences in the amount of force must generate to move a given load

20 Mechanical Advantage A small effort applied over a relatively long distance can be used to move a large load over a small distance Such a lever operates at a mechanical advantage and is commonly called a power lever because it can lift heavy loads

21 Mechanical Disadvantage
When the load is far from the fulcrum and the force is applied near the fulcrum, the force exerted by the muscle must be greater than the load moved These levers are useful because they allow the load to move rapidly through a large distance and are called speed levers

22 Lever Systems Regardless of type, all levers follow the same basic principle: Effort farther than load from fulcrum = mechanical advantage Effort nearer than load to fulcrum = mechanical disadvantage Depending on the relative position of the three elements (effort, fulcrum, load) a lever is classified as either a first, second, or third class lever

23 First Class Levers In first class levers the effort is applied at one end of the lever and the load is at the other end with the fulcrum in between them (LFE) Extension/flexion of the head, other exist but usually operate at a mechanical disadvantage

24 Second Class Levers In second class levers the effort is applied at one end, the fulcrum is at the other, with the load somewhere in between (FLE) Plantar flexion of the foot

25 Third Class Levers In third class levers, the effort is applied at a point between the load and the fulcrum (LEF) These levers operate with great speed and always at a mechanical disadvantage Most levers of the body are third class levers which permit an insertion close to the joint and allow rapid movement with little shortening of the muscle

26 Which Lever is it? Fulcrum in the middle? 1st Class
Load in the middle? 2nd Class Effort in the middle? 3rd Class

27 Lever Summary Difference in the positioning of the three elements modify muscle activity with respect to Speed on contraction Range of movement Weight of the load that can be lifted Speed levers act at a mechanical disadvantage Force is lost, but speed is gained Power levers act at a mechanical advantage Force is gained, but speed is lost

28 Major Skeletal Muscles
There are over 600 muscles in the body Approximately 125 are presented in text There will be 55 assigned to you to learn As you learn these muscles try to relate to its attachments and position and what joint(s) it acts across The best way to learn muscle actions is to act them out in your body



31 Muscle of Head: Facial Expression
Table 10.1

32 Muscles of Head: Facial Expression
Promote facial expression and non-verbal expression Highly variable in shape and strength Unusual in that they insert into skin or other muscles and not bone Innervated by Cranial nerve VII (facial)

33 Muscles of Head: Mastication

34 Muscles of Head: Mastication
Four pairs of muscles are involved with mastication Chewing and biting Masseter Temporalis Grinding movements Pterygoid Buccinator Trigeminal and Facial nerves

35 Muscles of Head: Tongue Movement
Table 10.2

36 Muscles of Head: Tongue Movement
The extrinsic muscles of the tongue serve to anchor and move the tongue These muscles serve to protrude, depress, and retract the tongue Innervated by the hypoglossal nerve

37 Muscle that Promote Swallowing
Table 10.8

38 Muscles that Promote Swallowing
Lateral view of the constrictor muscles of the pharynx These muscles are shown in their proper anatomical relationship

39 Muscles of Anterior Neck & Throat
Table 10.3

40 Muscles of Anterior Neck & Throat
Most of these muscles are involved with the coordinated action of swallowing which have the following sequence Widening the pharynx and closing the larynx Closing the superior nasal cavity Propulsion of food through the pharynx into the esophagus Return of musculature to normal positioning

41 Muscles of Neck Sternocleidomastoid is a head flexor
Scalenes contribute to lateral flexion of the neck Splenius is a head extensor

42 Muscles of Neck The head is moved by muscles originating from the axial skeleton which include Sternocleidomastoid / head flexors Scalenes / lateral head flexion Splenius / head extension

43 Muscles of Vertebral Column

44 Muscle of the Vertebral Column
Trunk extension is effected by the deep muscles of the back The erector spinae is the largest of the group and consists of three bands Iliocostalis Longissimus Spinalis Other muscles of the vertebral column include Semispinalis / extends head Quadratus lumborum / Lateral flexion

45 Muscle of the Thorax: Breathing

46 External Intercostals
O - Inferior border of rib above I - Superior border of rib below A - Pulls ribs upward to aid in respiration

47 Internal intercostals
O - Superior border of rib below I - Inferior border of rib above Draws ribs together; aids in expiration

48 Muscles of the Thorax: Breathing

49 Diaphragm O - Inferior border of rib cage, costal cartilages of last 6 ribs, and lumber vertabrae I - Central tendon A - Inspiration

50 Muscles of the Abdominal Wall

51 Muscles of Abdominal Wall
The anterior and lateral abdominal wall has no bony reinforcement It is composed of four paired muscles, their investing fasciae and their aponeuroses The muscles of the abdominal wall include Rectus abdominis External oblique Internal oblique Transverse abdominis

52 Muscles of the Abdominal Wall

53 Muscles of the Abdominal Wall
Illustration of how the aponeuroses of the lateral abdominal muscles contribute to the rectus abdominis sheath Enclosure of the Rectus abdominis within the aponeuroses prevents anterior protrusion or bowstringing of the muscle The Linea alba represents the central fusion of the aponeurses along the midline

54 Rectus abdominis O - Pubic crest and symphasis
I - xiphoid process and costal cartilages of ribs 5 - 7 A - Flex and rotate lumbar region of the vertebral column

55 External oblique O - by fleshy strips from outer surfaces of ribs 5-7
I - Linea alba; pubic crest and tubercle via aponeurosis A - flexing vertebral column

56 Internal oblique O -Lumbodorsal fasica, iliac crest and inguinal ligament I - Linea alba, pubic crest and last 3 ribs A - Flex vertebral column

57 Transverse abdominis O - inguinal ligament, lumbo- dorsal fascia, cartilages of last 6 ribs, iliac crest I - Linea alba, pubic crest A - compresses abdominal contents

58 Muscles of the Pelvic Floor

59 Muscles of the Pelvic Floor
Stretching between the two sides of the pelvic arch is the urogenital diaphram The Sphinter urethrae surrounds the urethra and allow voluntary urination

60 Muscles of the Pelvic Floor
Superficial space contains muscles (Ischocavernosus, Bulbospongiosus) that help maintain erection of the penis and clitoris The external anal sphinter encircles the anus and allows for voluntary control of defectation

61 Muscles of the Anterior Thorax

62 Pectoralis minor O - anterior surfaces of ribs 3-5
I - coracoid process of scapula A - ribs fixed draws scapula forward and downward

63 Serratus anterior O - ribs 1-9
I - entire anterior surface of vertebral border of scapula A - Protract the scapula; rotates scapula

64 Muscles of the Posterior Thorax

65 Trapezius O - Occipital bone, ligamentum nuchae, spines of C7 & all thoracic vert. I - Acromium and spine of scapula and lateral 1/3 of clavicle A - elevate and rotate scapula

66 Levator scapulae O - transverse processes of C1 - C4
I - superior angle of scapula A - elevates and adducts scapula

67 Rhomboid major O - spinous processes of T2 - T5
I - medial border of scapula A - retract; rotate; and stabilize scapula

68 Rhomboid minor O - spinous processes of C7 and T1
I - medial border of scapula A - retract; rotate; and stabilize scapula

69 Muscles Crossing the Shoulder Joint
A total of nine muscles cross the shoulder joint to insert on the humerus The three prime movers of the shoulder joint are Pectoralis major Lastissimus dorsi Deltoid The remaining six muscles are synergists and fixators Four of these six are muscles of the rotator cuff

70 Muscles Crossing the Shoulder Joint

71 Pectoralismajor O - clavicle, sternum, and cartilages of ribs 1 - 6
I - greater tubercle of humerus A - arm flexion, medial arm rotation, arm adduction

72 Latissimus dorsi O - spines of T6 - T12 and L1 - L5 etc
I - Inter- tubicular groove of humerus A - arm extension, adduction and med. rotation

73 Deltoid O - Lateral 1/3 of clavicle, acromium, and spine of scapula
I - Deltoid tuberosity of humerus A - arm abduction; flex/ ext. arm; med./ lat. rotate arm

74 Subscapularis O - subscapular fossa of scapula
I - lesser tubercle of humerus A - medial rotator of arm

75 Supraspinatus O - supra spinatus fossa of scapula
I - superior part of greater tubercle of humerus A - holds head of humerus in glenoid fossa to stabilize shoulder joint

76 Infraspinatus O - infra spinatus fossa of scapula
I - greater tubercle of humerus A - laterally rotates scapula

77 Teres minor O - lateral border of dorsal scapular surface
I - greater tubercle of humerus A - laterally rotates scapula

78 Teres major O - posterior surface of scapula at inferior angle
I - lesser tubercle of humerus A - extends, medially rotates and adducts humerus

79 Coraco- brachialis O - coracoid process of scapula
I - medial surface of shaft of humerus A - flexion and adduction of humerus

80 Muscles Crossing the Elbow Joint
Since the elbow is a hinge joint the movement promoted by these muscles are limited almost to flexion and extension of the forearm There are three muscles anteriorly Biceps brachii Brachialis Brachioradialis There is one muscle posteriorly Triceps brachii

81 Muscles Crossing the Elbow Joint

82 Triceps brachii O - long head/ infraglenoid tubercle; lat. and medial heads / posterior humerus; I - Olecranon process of ulna A - forearm extensor; long head assist in adduction

83 Biceps brachii O - short head/ coracoid process of scapula; long head / supra glendoid tubercle I - radial tuberosity A - flexes arm and forearm; supinates

84 Brachialis O - anterior, distal humerus I - coracoid process of ulna
A - forearm flexor

85 Brachio radialis O - lateral supracondylar ridge
I - styloid process of radius A - forearm flexion; a semi pronated position gives it its best mechanical advantage

86 Muscles of Forearm Muscles of the forearm are divided equally into flexors and extensors Flexors on the medial epicondyle Extensors on the lateral epicondyle

87 Pronator teres O - medial epicondyle of humerus
I - lateral radius at midshaft A - pronates forearm; weak elbow flexor

88 Flexor carpi radialis O - medial epicondyle of humerus
I - base of second and third metacarpals A - powerful wrist flexor;

89 Palmaris longus O - medial epicondyle of humerus
I - palmer aponeurosis A - weak wrist flexor; tenses palmer aponeurosis

90 Flexor carpi ulnaris O - medial epicondyle of humerus
I - pisiform bone and base of 5th metacarpal A - flexor of wrist

91 Muscles Crossing the Hip and Knee
Muscles crossing the hip and knee can be grouped into Hip flexors (4) Gluteal muscles (3) Medial compartment (5 adductors) Anterior compartment (4 knee extensors) Posterior compartment (3 knee flexors) Lateral rotators (5)

92 Muscles Crossing the Hip and Knee

93 Iliacus O - iliac fossa I - lesser trochanter of femur A - hip flexion

94 Psoas major O - transverse processes and bodies of T12 and all lumbar vertebrae I - lesser trochanter of femur A - hip flexion and lateral hip flexion

95 Psoas minor O - Transverse processes and bodies of T12 and L1
I - Rim of acetabulum A - flexes lumbar vertebrae

96 Sartorius O - anterior superior iliac spine
I - medial aspect of proximal tibia A - Flexes and laterally rotates thigh; flexes knee

97 Adductors Adductors Adductor magnus Adductor longus Adductor brevis
Pectineus Gracilis

98 Adductor magnus O - ischial and pubic rami and ischial tuberosity
I - linea aspera and adductor tubercle A - adducts and laterally rotates thigh

99 Adductor longus O - pubis near pubic symphysis I - linea aspera
A - adducts, flexes and laterally rotates thigh

100 Adductor brevis O - body and inferior ramus of pubis I - linea aspera
A - adducts and laterally rotates thigh

101 Pectineus O - pectineal line of pubis I - lesser trochanter of femur
A - adducts, flexes, and laterally rotates thigh

102 Gracilis O - inferior ramus and body of pubis
I - medial surface of tibia just inferior to media condyle A - adducts thigh, flexes and medially rotates thigh

103 Quadriceps femoris Muscles include Rectus femoris Vastus lateralis
Vastus medialis Vastus intermedius

104 Rectus femoris O - anterior inferior iliac spine
I - patella and tibial tuberosity A - extends knee and flexes thigh at hip

105 Vastus lateralis O - greater trochanter, intertrochanteric line
I - patella and tibial tuberosity A - extends knee

106 Vastus medialis O - linea aspera, intertrochanteric line
I - patella and tibial tuberosity A - extends knee

107 Vastus intermedius O - anterior and lateral surfaces of proximal shaft of femur I - patella and tibial tuberosity A - extend knee

108 Tensor fascia latae O - anterior aspect of iliac crest
I - iliotibial tract A - flexes and abducts thigh

109 Gluteal Muscles

110 Gluteus maximus O - dorsal ilium, sacrum and coccyx
I - gluteal tuberosity of femur A - thigh extension

111 Gluteus medius O - between anterior and posterior gluteal lines on lateral surface of ilium I - greater trochanter of femur A - abducts and medially rotates thigh

112 Gluteus minimus O - between anterior and inferior gluteal lines on external surface of femur I - greater trochanter of femur A - abducts and medially rotates thigh

113 Lateral rotators In this view cutting the gluteal muscles reveals the lateral rotators of the thigh

114 Lateral rotators In this view cutting the gluteal muscles reveals the lateral rotators of the thigh

115 Biceps femoris O - (long) ischial tuberosity, (short) linea aspera
I - head of fibula and lateral condyle of tibia A - extends thigh and flexes knee, laterally rotates leg

116 Semi- tendinosus O - ischial tuberosity
I - medial aspect of upper tibial shaft A - extends thigh at hip; flexes knee, medially rotates leg

117 Semi- membranosus O - ischial tuberosity I - medial condyle of tibia
A - extends thigh and flexes knee, medially rotates leg

118 Muscles -Anterior Compartment
Muscles of the anterior compartment are primarily toes extensors and dorsiflexors Tibialis anterior Extensor digitorum longus Extensor hallucis longus Peroneus tertius Important in walking during the recovery phase of gait

119 Tibialis anterior O - lateral condyle and upper 2/3 of tibia
I - inferior medial surface of medial cuneiform and 1st metatarsal bone A - dorsiflexion, inverts foot

120 Extensor digitorum longus
O - lateral condyle of tibia, proximal 3/4 of fibula I - 2nd & 3rd phalanges of toes 2-5 via extensor expansion A - Dorsiflexion, toe extension

121 Peroneus tertius O - distal surface of fibula and interosseous membrane I - dorsum of fifth metatarsal A - dorsiflexes and everts foot

122 Extensor hallucis O - anteriomedial fibula shaft and interosseous membrane I - distal phalanx of great toe A - extends great toe, dorsiflexes foot

123 Muscles - Lateral Compartment
Muscles of the lateral compartment are primarily plantar flex and evert the foot Peroneus longus Peroneus brevis

124 Peroneus longus O - head and upper portion of fibula
I - under the foot to first metatarsal and medial cuneiform A - plantar flexes and everts foot

125 Peroneus brevis O - distal shaft of fibula
I - proximal end of the 5th metatarsal A - Plantar flexes and everts foot

126 Muscles of Posterior Compartment
Muscles of the posterior compartment are primarily plantar flexors and flex the toes Gastrocnemius Soleus Tibialis posterior Flexor digitorum longus Flexor hallucis longus

127 Gastrocnemius O - from medial and lateral condyles of femur
I - calcaneus via calcaneal tendon A - plantar flexes foot, flexes knee

128 Soleus O - superior tibia, fibula and interosseus membrane
I - calcaneus via calcaneal tendon A - plantar flexes ankle

129 Plantaris O - posterior femur above lateral condyle I - calcaneus
A - plantar flexion, knee flexion

130 Popliteus O - lateral condyle of femur I - proximal tibia
A - flexes and rotates knee medially to unlock knee from full extension

131 Flexor digitorum longus
O - posterior tibia I - distal phalanges of toes 2-5 A - plantar flexes and flexes toes

132 Flexor hallicus longus
O - medial part of shaft of fibula, interosseous membrane I - distal phalanx of great toe A - plantar flexes and inverts foot, flexes great toe

133 Tibialis posterior O - superior tibia and fibula and interosseous membrane I - tarsals and metatarsals 2-4 A - inversion, plantar flexion

134 Intrinsic Muscles of the Foot
The intrinsic muscles of the foot help to flex, extend, abduct, and adduct the toes Collectively the muscles support the arches of the foot assisted by some tendons of leg muscles The muscles occur in four layers from superficial to deep

135 Intrinsic Muscles of the Foot
Muscles of the second layer flex, adduct, and abduct the toes Muscles include Flexor digitorum brevis Abductor hallucis Abductor digiti minimi

136 Intrinsic Muscles of the Foot

137 Intrinsic Muscles of the Foot

138 Intrinsic Muscles of the Foot

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