1 Chapter 11: The Muscular System. 2 The Muscular System Consists only of skeletal muscles Muscle...

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Chapter 11:

The Muscular System

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The Muscular System

• Consists only of skeletal muscles• Muscle organization affects power,

range, and speed of muscle movement

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Fascicles

• Muscle cells (fibers) are organized in bundles (fascicles)

• Classification of Skeletal Muscles– By the way fascicles are organized– By relationships of fascicles to tendons

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Muscle Organization

• Groups of fibers are organized into fascicles

• Fibers in fascicle run parallel to fascicle, but fascicle can be arranged in 4 different shapes with respect to tendon:

1. Parallel Muscles2. Convergent Muscles3. Pennate Muscles

- Unipennate, Bipennate, Multipennate

4. Circular Muscles

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1. Parallel Muscles

• Fascicles run parallel to length of the muscle

• Most skeletal muscles are arranged this way

• Able to change length extensively

• Can move load over a great distance

Figure 11–1a

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Parallel Muscle Body

• The center or body of the muscle thickens when parallel muscle contracts

• Tension– Depends on total number of myofibrils

• Directly relates to cross section of muscle• 1 in.2 (6.45 cm2) of cross section develops

50 lb (23 kg) of tension

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2. Pennate Muscles • Fascicles are arranged at an angle to tendonA. Unipennate: Fascicle angled on one side of tendonB. Bipennate: Tendon in middle with angled fascicles on either

sideC. Multipennate: - Branched tendon with fascicles organized around each

branch**Pennate muscles produce more tension than parallel

muscles but cannot move so far, less distance producedA. Unipennate B. Bipennate

C. Multipennate

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Pennate Muscles

• Unipennate: – fibers on 1 side of tendon – e.g., extensor digitorum

• Bipennate:– fibers on both sides of tendon– e.g., rectus femoris

• Multipennate:– tendon branches within muscle– e.g., deltoid

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3. Convergent Muscles

• Fascicles spread out like a fan on one end and converge to a single point on the other

• Produce less tension and distance than parallel muscles but– Independent

contraction of fascicles can produce different movement from the same muscle

– Provides versatility• Muscle fibers pull in

different directions, depending on stimulation Figure 11–1b

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4. Circular Muscles

• Also called sphincters

• Concentric arrangement of fascicles

• Function:– Decrease diameter of

openings to guard entrances and exits

• e.g., obicularis oris

Figure 11–1f

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Why does a pennate muscle generate more tension than does

a parallel muscle of the same size?

1. Parallel fibers do not respond to calcium.

2. A pennate muscle contains more muscle fibers.

3. Muscle force is concentrated on the insertion in pennate muscles.

4. This is not a true statement.

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Which type of muscle would you expect to be guarding the

opening between the stomach and the small intestine?

1. convergent muscle2. multipennate muscle3. parallel muscle4. circular muscle

(sphincter)

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Muscle Terminology• Muscles have 1 fixed point of attachment

(origin) and 1 moving point of attachment (insertion)

• Origin: – Where the fixed end of the muscle attached to

bone, cartilage, or CT– Origin is usually proximal to insertion

• Insertion:– Where the moveable end attaches

• Action:– The specific movement produced by the muscle

during contraction•e.g., flexion, extension, adduction, etc.

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Muscles interact to produce or oppose

movements.

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Muscle Interactions

• Muscles work in groups to maximize efficiency

• Smaller muscles reach maximum tension first, followed by larger, primary muscles

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Muscle Terminology• Muscle often work in groups to increase

tension or fine tune movement• Different muscles serve different function:

– Agonist: •prime mover, muscle most responsible for the

movement– Synergist:

•a muscle with the same action as the agonist•assists agonist at the beginning of contraction

when fiber length is not optimal for agonist– helps start motion or stabilize origin of

agonist (fixator)– Antagonist:

•a muscle whose action opposes the agonist– produces the opposite action to fine tune

movement by the agonist

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Muscle Opposition

• Agonists and antagonists work in pairs:– when 1 contracts, the other stretches– i.e. flexors–extensors

abductors–adductors

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The name of a muscle helps identify its location, appearance, or function.

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Descriptive Names for Skeletal Muscles

1. Location in the body2. Fascicle organization3. Relative position4. Structure, Size and Shape5. Origin and insertion6. Action

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Naming Muscles• Names of muscle are derived from aspects

of their features:1. Location:

- Named for part of the body where they’re located- e.g. Brachii, Abdominis

2. Fascicle Organization: - Named for how fascicles are organized with respect to the body- e.g. Rectus = straight Oblique = angle

3. Relative Position: - Named for depth when layered- e.g. Externus/Superficialis = top, surface Internus/Profundus = deep

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Naming Muscles4. Structure, Size and Shape:

A. Number of tendons- e.g. triceps, biceps

B. Shape of Muscle- e.g. trapezius = trapezoid deltoid = triangle soleus = fish

C. Size of muscle relative to others- Major = bigger- Maximus = biggest- Longus = long- Vastus = great

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Naming Muscles5. Origin and Insertion:

- Name of regions of attachment, origin first, insertion second

- e.g. sternocleidomastoidOrigin = manubrium of sternum and

medial clavicleInsertion = mastoid process

6. Action:- Named for action performed and region

acted upon- e.g. extensor digitorum

Usually multiple naming schemes are combined to name the muscle:

e.g. flexor carpi ulnaris* Individual muscles, orgins, insertions and actions

are examined in lab.

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Naming Skeletal Muscles

Table 11–1 (1 of 2)

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Naming Skeletal Muscles

Table 11–1 (2 of 2)

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Effects of Aging on the Muscular System

1. Skeletal muscle fibers become smaller in diameter

2. Skeletal muscles become less elastic:

– develop increasing amounts of fibrous tissue (fibrosis)

3. Decreased tolerance for exercise4. Decreased ability to recover from

muscular injuries

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Muscle A abducts the humerus, and muscle B adducts the

humerus. What is the relationship between

these two muscles?

1. synergists2. antagonists3. agonists4. fixators

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What does the name flexor carpi radialis longus tell you about this

muscle?

1. its size2. its function3. its location4. 1, 2, and 3 are correct

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A Closer Look at the Muscular

System

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Axial and Appendicular Muscles

Figure 11–3a

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Axial and Appendicular Muscles

Figure 11–3b

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Divisions of the Muscular System

1. Axial muscles:– position head and spinal column– move rib cage– 60% of skeletal muscles

2. Appendicular muscles:– support pectoral and pelvic girdles– support limbs– 40% of skeletal muscles

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The Axial Muscles

• Divisions based on location and function:– muscles of head and neck– muscles of vertebral column– oblique and rectus muscles– muscles of pelvic floor

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Muscles of Facial Expression

Figure 11–4b

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Summary: Muscles of Facial Expression

Table 11–2 (1 of 2)

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Summary: Muscles of Facial Expression

Table 11–2 (2 of 2)

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Anterior Muscles of the Neck

Figure 11–9

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Oblique and Rectus Muscles• Lie within the body wall

Figure 11–11a, b

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Functions of Oblique and Rectus Muscles

• Oblique muscles:– compress underlying structures– rotate vertebral column

• Rectus muscles:– flex vertebral column

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Oblique Muscles

• Thoracic region:– intercostal muscles (external and

internal intercostals):• respiratory movements of ribs

• Abdominopelvic region (same pattern as thoracic):– external oblique muscles – internal oblique muscles

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Rectus Group

• Rectus abdominis:– between xiphoid process and pubic

symphysis– divided transversely by tendinous

inscriptions

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Oblique Muscles

Table 11–9 (1 of 2)

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Oblique and Rectus Muscles

Table 11–9 (2 of 2)

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The structures and functions of the

major muscle groups of the upper and lower

limbs.

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The Appendicular Muscles

Figure 11–13b

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Figure 11–13a

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• Position and stabilize pectoral and pelvic girdles

• Move upper and lower limbs– Move the arm– Move the forearm and hand– Move the hand and fingers

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Muscles that Position the Pectoral Girdle

Figure 11–14b

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Figure 11–14a

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• Trapezius:– superficial– covers back and neck to base of skull– inserts on clavicles and scapular spines

• Rhomboid and levator scapulae:– deep to trapezius– attach to cervical and thoracic vertebrae– insert on scapular border

• Serratus anterior:– on the chest– originates along ribs– inserts on anterior scapular margin

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Tables 11–11

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Muscles that Move the Arm

Figure 11–15a

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Figure 11–15b

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9 Muscles that Move the Arm

• Deltoid: – the major abductor (away from

longitudinal axis)

• Teres major/minor: – produce rotation at shoulder

• Coracobrachialis: – attaches to scapula– produces flexion and adduction at

shoulder

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9 Muscles that Move the Arm

• Pectoralis major: – between anterior chest and greater

tubercle of humerus– produces flexion at shoulder joint

• Latissimus dorsi:– between thoracic vertebrae and

humerus– produces extension at shoulder joint

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The Rotator Cuff

• Muscles involved in shoulder rotation– supraspinatus, subscapularis,

infraspinatus, teres minor,and their tendons

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Table 11–12

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Baseball pitchers sometimes suffer from rotator cuff injuries.

Which muscles are involved in this type of injury?

1. rhomboid major and minor, teres major and minor muscles

2. teres major, teres minor and serratus anterior muscles

3. pectoralis major and minor muscles

4. supraspinatus, infraspinatus, subscapularis, and teres minor muscles

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Muscles that Move the Forearm and Hand

Figure 11–16a

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Figure 11–16b

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• Originate on humerus and insert on forearm

• Exceptions:– the major flexor (biceps brachii)

•mainly on anterior and medial surfaces– the major extensor (triceps brachii)

•mainly on posterior and lateral surfaces of arm

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• Biceps brachii:– flexes elbow– stabilizes shoulder joint– originates on scapula– inserts on radial tuberosity

• Triceps brachii:– extends elbow– originates on scapula– inserts on olecranon

• Brachialis and brachioradialis:– flex elbow

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• Flexor carpi ulnaris: – superficial– flexes wrist– adducts wrist

• Flexor carpi radialis: – superficial– flexes wrist– abducts wrist

• Extensor carpi radialis:– superficial– extends wrist– abducts wrist

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• Extensor carpi ulnaris:– superficial– extends wrist– adducts wrist

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Summary: Muscles that Move the Forearm and Hand

Table 11–13 (1 of 2)

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Summary: Muscles that Move the Forearm and Hand

Table 11–13 (2 of 2)

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Muscles that Move the Hand and Fingers

Figure 11–17a, b

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Muscles that Move the Hand and Fingers

Figure 11–17c, d

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Summary: Muscles that Move the Hand and Fingers

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Muscles of the Pelvis and Lower Limbs

• Pelvic girdle is tightly bound to axial skeleton:– permits little movement– has few muscles

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Muscles that Position the Lower Limbs

1. Muscles that move the thigh2. Muscles that move the leg3. Muscles that move the foot and

toes

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Muscles that Move the Thigh

Figure 11–19a, b

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Figure 11–19c, d

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• Gluteal muscles • Lateral rotators • Adductors • Iliopsoas

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• Gluteal Muscles– Gluteus maximus:

• largest, most posterior gluteal muscle• produces extension and lateral rotation at

hip

• Adductors– Gracilis:

• hip flexion and adduction

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Muscles that Move the Leg

Figure 11–20a

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Figure 11–20b, c

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• Flexors of the knee:– originate on the pelvic girdle

• Extensors of the knee:– originate on the femoral surface– insert on the patella

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Flexors and Extensors of the Knee

• Flexors of the Knee– Biceps femoris– Semimembranosus– Semitendinosus– Sartorius:

• originates superior to the acetabulum

• Extensors of the Knee– 4 muscles of the quadriceps femoris:

• 3 vastus muscles• rectus femoris muscle

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Hamstrings

• Hamstrings are made up of:– biceps femoris– semimembranosus– semitendinosus

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Table 11–17 (1 of 2)

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Table 11–17 (2 of 2)

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You often hear of athletes who suffer a pulled hamstring. To what does this phrase refer?

1. biceps femoris, gracilis, and adductor magnus damage

2. rectus femoris, vastus lateralis and vastis medialis damage

3. semitendinosus, biceps femoris, and semimembranosus muscle damage

4. sartorius, gracilis and rectus femoris damage

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Muscles that Move the Foot and Toes

Figure 11–21a, b

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Figure 11–21c, d

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• Extrinsic muscles that move the foot and toes include:– muscles that produce extension at the

ankle– muscles that produce flexion at the ankle– muscles that produce extension at the toes– muscles that produce flexion at the toes

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Muscles that Produce Movement at the Ankle

• Muscles that Produce Extension at the Ankle – Gastrocnemius– Soleus– Fibularis– Tibialis posterior

• Muscles that Produce Flexion at the Ankle – Tibialis anterior:

•opposes the gastrocnemius

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The Achilles Tendon

• The calcaneal tendon (Achilles tendon):– shared by the gastrocnemius and

soleus

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Muscles the Produce Movement of the Toes

• Muscles that Produce Extension at the Toes– Extensor digitorum longum

• Muscles that Produce Flexion at the Toes– Flexor digitorum longum

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SUMMARY

• Effects of muscle structure on function• Organization of skeletal muscle fibers:

– parallel, convergent, pennate, circular• Relationships between levers and

movement• Actions of first, second, and third class

levers• Origins and insertions of skeletal muscles• Actions of skeletal muscles:

– agonist, antagonist, synergist• How skeletal muscles are named

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SUMMARY

• Structures and functions of axial muscles:– muscles of head and neck– muscle of vertebral column– oblique and rectus muscles– muscles of pelvic floor

• Structures and functions of the appendicular muscles:– muscles of shoulders and upper limbs– muscles of pelvis and lower limbs

• Effects of aging on the muscular system

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1 Chapter 11: The Muscular System. 2 The Muscular System Consists only of skeletal muscles Muscle...

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