Chapter 11: The Muscular System Biol 141 A&P. The Muscular System Consists only of skeletal muscles...

Chapter 11:The Muscular System

Biol 141 A&P

The Muscular System

• Consists only of skeletal muscles

• How are fascicles arranged in the various types of muscles, and what are the resulting functional differences?

Muscle Organization and Function

• Muscle organization affects power, range, and speed of muscle movement

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

Organization of Skeletal Muscle Fibers

• 4 patterns of fascicle organization:• 1) Parallel-

– Fibers parallel to the long axis of muscle

- e.g., biceps brachii• 2) Convergent-• 3) Pennate-• 4) Circular-

Parallel Muscles

Figure 11–1a

Parallel Muscle Body• The center or body of the muscle

thickens when parallel muscle contracts• Parallel muscles contract about 30%

Parallel Muscle 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

Convergent Muscles

Figure 11–1b

Convergent Muscles

• A broad area converges on attachment site (tendon, aponeurosis, or raphe)

• Muscle fibers pull in different directions, depending on stimulation

• e.g., pectoralis muscles

Pennate Muscles

Figure 11–1c, d, e

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

Pennate Muscles

• Form an angle with the tendon• Do not move as far as parallel

muscles• Contain more myofibrils than

parallel muscles• Develop more tension than parallel

muscles

Circular Muscles

Figure 11–1f

Circular Muscles

• Also called sphincters • Open and close to guard entrances

of body• e.g., obicularis oris

Skeletal Motion

• Skeletal muscles attach to skeleton, produce motion

• Type of muscle attachment affects power, range, and speed of muscle movement

What are the classes of levers, and how do they

make muscles more efficient?

Levers• Mechanically, each bone is a lever

(a rigid, moving structure):– and each joint a fulcrum (a fixed point)

• Muscles provide applied force (AF):– required to overcome resistance (R)

Functions of a Lever

• To change:– direction of an AF– distance and speed of movement

produced by an AF– effective strength of an AF

3 Classes of Levers

• Depend on the relationship between applied force, fulcrum, and resistance:– first class– second class– third class

First, Second, and Third-Class LeversPLAYPLAY

First-Class Levers

Figure 11–2a

First-Class Levers

• Seesaw is an example• Center fulcrum between applied

force and resistance• Force and resistance are balanced

Second–Class Levers

Figure 11–2b

Second-Class Levers

• Wheelbarrow is an example• Center resistance between applied

force and fulcrum• A small force moves a large weight

Third-Class Levers

Figure 11–2c

Third-Class Levers

• Most common levers in the body• Center applied force between

resistance and fulcrum• Greater force moves smaller

resistance• Maximizes speed and distance

traveled

KEY CONCEPT

• Skeletal muscles can shorten to 70% of resting length

• Power, speed, and range of movement

• Depend on positions of muscle attachment

• Relative to joints

How are actions of a muscle based on the

relative positions of its origin and insertion?

Origins and Insertions

• Muscles have 1 fixed point of attachment (origin) and 1 moving point of attachment (insertion)

• Most muscles originate or insert on the skeleton

• Origin is usually proximal to insertion

Actions

• Movements produced by muscle contraction

• Body movements – e.g., flexion, extension, adduction,

etc.

• Described in terms of bone, joint, or region

How do muscles interact to produce or oppose

movements?

Muscle Interactions

• Muscles work in groups to maximize efficiency

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

Muscle Terminology Based on Function

• Agonist (prime mover):– produces a particular movement

• Antagonist:– opposes movement of a particular agonist

• Synergist:– a smaller muscle that assists a larger

agonist– helps start motion or stabilize origin of

agonist (fixator)

Muscle Opposition

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

adductors, etc.

How does the name of a muscle help identify its location, appearance, or

function?

Names of Skeletal Muscles

• Correct names of muscles include the term muscle

• Exceptions: – platysma– diaphragm

Naming Skeletal Muscles

Table 11–1 (1 of 2)

Naming Skeletal Muscles

Table 11–1 (2 of 2)

Descriptive Names for Skeletal Muscles

1. Location in the body-Identifies body regions: e.g.- temporalis muscle

2. Origin and insertion- First part of name indicates origin, Second part of name indicates insertion: e.g. genioglossus muscle

3. Fascicle organization-Describes fascicle orientation within muscle:

– i.e., rectus (straight), transversus, oblique

Descriptive Names for Skeletal Muscles

4. Relative position- Externus (superficialis):– visible at body surface

• Internus (profundus):deep muscles• Extrinsic:muscles outside an organ• Intrinsic:muscles inside an organ5. Structural characteristics- Number of tendons:

– bi = 2, tri = 3

• Shape: trapezius, deltoid, rhomboid• Size-6. Action- Movements: e.g., flexor, extensor,

retractor• Occupations or habits: e.g., risor = laughter

Names for Muscle Size (1 of 2)

• Longus = long• Longissimus = longest• Teres = long and round• Brevis = short• Magnus = large• Major = larger• Maximus = largest• Minor = small• Minimus = smallest

Axial and Appendicular Muscles

Figure 11–3a

Axial and Appendicular Muscles

Figure 11–3b

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

What are the principle axial muscles of the body, their origins, insertions, actions, and innervation?

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

3D Peel-Away of Muscles of the Head and NeckPLAYPLAY

6 Muscle Groups of the Head and Neck

• Muscles of facial expression:– originate on skull

• Extrinsic eye muscles:– originate on surface of orbit– control position of eye


• Muscles of mastication:– move the mandible

• Muscles of the tongue:– names end in glossus

• Muscles of the pharynx:– begin swallowing process


• Anterior muscles of the neck:– control position of larynx– depress the mandible– support tongue and pharynx

Muscles of Facial Expression

Figure 11–4a


Figure 11–4b


• Orbicularis oris:– constricts the mouth opening

• Buccinator:– moves food around the cheeks

• Muscles of the epicranium (scalp)

Muscles of the Epicranium (Scalp)

• Temporoparietalis• Occipitofrontalis:

– frontal and occipital bellies– separated by epicranial aponeurosis

• Platysma:– covers anterior surface of neck

Summary: Muscles of Facial Expression

Table 11–2 (1 of 2)

Summary: Muscles of Facial Expression

Table 11–2 (2 of 2)

Extrinsic Eye Muscles

• Also called extra-ocular muscles

Figure 11–5a, b

Extrinsic Eye Muscles

Figure 11–5c

Inferior rectusMedial rectusSuperior rectusLateral rectusInferior obliqueSuperior oblique

Summary: Extrinsic Eye Muscles

Table 11–3

Muscles of Mastication

Figure 11–6

3 Muscles of Mastication

• Masseter:– the strongest jaw muscle

• Temporalis:– helps lift the mandible

• Pterygoid muscles:– position mandible for chewing

Summary: Muscles of Mastication

Table 11–4

Muscles of the Tongue

Figure 11–7

4 Muscles of the Tongue

• Palatoglossus:– originates at palate

• Styloglossus:– originates at styloid process

• Genioglossus:– originates at chin

• Hypoglossus:– originates at hyoid bone

Summary: Muscles of the Tongue

Table 11–5

Muscles of the Pharynx

Figure 11–8

3 Muscles of the Pharynx

• Pharyngeal constrictor muscles:– move food into esophagus

• Laryngeal elevator muscles:– elevate the larynx

• Palatal muscles:– lift the soft palate

Summary: Muscles of the Pharynx

Table 11–6

Anterior Muscles of the Neck

Figure 11–9

6 Anterior Muscles of the Neck • Digastric:

– from chin to hyoid– and hyoid to mastoid

• Mylohyoid:– floor of the mouth

• Geniohyoid:– between hyoid and chin

• Stylohyoid:– between hyloid and styloid

• Sternocleidomastoid:– from clavicle and sternum to mastoid

• Omohyoid:– attaches scapula, clavicle, first rib, and hyoid

Summary: Anterior Muscles of the Neck

Table 11–7

Muscles of the Vertebral Column

Figure 11–10a

Muscles of the Vertebral Column

• Spinal extensors or erector spinae muscles (superficial and deep)

• Spinal flexors (transversospinalis)

Superficial Spinal Extensors• Spinalis group• Longissimus group• Iliocostalis group

Deep Spinal Extensors• Semispinalis group• Multifidus muscle• Interspinalis muscles• Intertransversarii muscles• Rotatores muscles

Spinal Flexors

• Neck:– longus capitis and longus colli – rotate and flex the neck

• Lumbar:– quadratus lumborum muscles – flex spine and depress ribs

Summary: Muscles of the Vertebral Column

Table 11–8 (1 of 2)

Summary: Muscles of the Vertebral Column

Table 11–8 (2 of 2)

Oblique and Rectus Muscles

• Lie within the body wall

Figure 11–11a, b


Figure 11–11a, c


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

• Rectus muscles:– flex vertebral column– oppose erector spinae

Oblique MusclesCervical region:– scalene muscles– flex the neck

Thoracic region:– intercostal muscles (external and

internal intercostals):• respiratory movements of ribs

– transversus thoracis:• cross inner surface of ribs

Oblique Muscles

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

• Transversus abdominis

Rectus Group• Rectus abdominis:

– between xiphoid process and pubic symphysis

– divided longitudinally by linea alba– divided transversely by tendinous

inscriptions

• Diaphragmatic muscle or diaphragm:– divides thoracic and abdominal cavities– performs respiration

Summary: Oblique and Rectus Muscles

Table 11–9 (1 of 2)

Summary: Oblique and Rectus Muscles

Table 11–9 (2 of 2)

Muscles of the Pelvic Floor

Figure 11–12a

Muscles of the Pelvic Floor

Figure 11–12b

Functions of Pelvic Floor Muscles

1. Support organs of pelvic cavity2. Flex sacrum and coccyx3. Control movement of materials

through urethra and anus

Perineum• Muscular sheet forming the pelvic

floor, divided into:– anterior urogenital triangle – posterior anal triangle

Pelvic Diaphragm– Deep muscular layer extending to

pubis:– supports anal triangle

Urogenital Diaphragm

• Deep muscular layer between pubic bones:– supports the pelvic floor – and muscles of the urethra

• Superficial muscles of the urogenital triangle:– support external genitalia

Summary: Muscles of the Pelvic Floor

Table 11-10 (1 of 2)

Summary: Muscles of the Pelvic Floor

Table 11-10 (2 of 2)

What are the principal appendicular muscles of

the body and their origins, insertions,

actions, and innervations?

The Appendicular Muscles

Figure 11–13a


Figure 11–13b


• Position and stabilize pectoral and pelvic girdles

• Move upper and lower limbs

Divisions of Appendicular Muscles

1) Muscles of the shoulders and upper limbs:

• Position the pectoral girdle• Move the arm• Move the forearm and hand• Move the hand and fingers

2) Muscles of the pelvis and lower limbs

3D Peel-Away of Muscles of the Pectoral GirdlePLAYPLAY

Muscles that Position the Pectoral Girdle

Figure 11–14a

Muscles that Position the Pectoral Girdle

Figure 11–14b

6 Muscles that Position the Pectoral Girdle

• 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

6 Muscles that Position the Pectoral Girdle

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

• Subclavius:– originates on ribs– inserts on clavicle

• Pectoralis minor:– attaches to scapula

Summary: Muscles that Position the Pectoral Girdle

Tables 11–11

Muscles that Move the Arm

Figure 11–15a

Muscles that Move the Arm

Figure 11–15b

9 Muscles that Move the Arm (1 of 3)

• Deltoid: – the major abductor

• Supraspinatus: – assists deltoid

• Subscapularis and teres major: – produce medial rotation at shoulder

3D Rotation: Muscles of the ArmPLAYPLAY


• Infraspinatus and teres minor: – produce lateral rotation at shoulder

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

shoulder


• 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

The Rotator Cuff

• Muscles involved in shoulder rotation– supraspinatus, subscapularis,

infraspinatus, teres minor,and their tendons

Summary: Muscles that Move the Arm

Table 11–12

Muscles that Move the Forearm and Hand

Figure 11–16a


Figure 11–16b


• Originate on humerus and insert on forearm

• Exceptions:– the major flexor (biceps brachii)– the major extensor (triceps brachii)

3D Rotation: Muscles of the Forearm and HandPLAYPLAY

Extensors and Flexors

• Extensors:– mainly on posterior and lateral

surfaces of arm

• Flexors:– mainly on anterior and medial

surfaces

13 Muscles that Move the Forearm and Hand

• Biceps brachii:– flexes elbow– stabilizes shoulder joint

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

• Brachialis and brachioradialis:– flex elbow– originates on scapula– inserts on radial tuberosity


• Anconeus:– opposes brachialis

• Palmaris longus:– superficial– flexes wrist

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


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

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

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

13 Muscles that Move the Forearm and Hand (8 of

8)• Pronator teres and supinator:

– originate on humerus and ulna– rotate radius

• Pronator quadratus:– originates on ulna– assists pronator teres

Summary: Muscles that Move the Forearm and Hand

Table 11–13 (1 of 2)

Summary: Muscles that Move the Forearm and Hand

Table 11–13 (2 of 2)

Muscles that Move the Hand and Fingers

Figure 11–17a, b


Figure 11–17c, d


• Also called extrinsic muscles of the hand

• Lie entirely within forearm• Only tendons cross wrist (in

synovial tendon sheaths)

Tendon Sheaths

• Extensor retinaculum: – wide band of connective tissue– posterior surface of wrist– stabilizes tendons of extensor

muscles

• Flexor retinaculum:– anterior surface of wrist– stabilizes tendons of flexor muscles

Summary: Muscles that Move the Hand and Fingers

Table 11–14

The Intrinsic Muscles of the Hand

Figure 11–18a

The Intrinsic Muscles of the Hand

Figure 11–18b

Summary: The Intrinsic Muscles of the Hand

Table 11–15 (1of 2)

Summary: The Intrinsic Muscles of the Hand

Table 11–15 (2of 2)

Muscles of the Pelvis and Lower Limbs

• Pelvic girdle is tightly bound to axial skeleton:

– permits little movement– has few muscles

Muscles that Position the Lower Limbs

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

Muscles that Move the Thigh

Figure 11–19a, b


Figure 11–19c, d


• Gluteal muscles • Lateral rotators • Adductors • Iliopsoas

3D Peel-Away of Muscles of the ThighPLAYPLAY

3D Peel-Away of Rectus MusclePLAYPLAY

Gluteal Muscles (1 of 2)

• Cover lateral surfaces of ilia• Gluteus maximus:

– largest, most posterior gluteal muscle– produces extension and lateral

rotation at hip

Gluteal Muscles (2 of 2)

• Tensor fasciae latae:– works with gluteus maximus– stabilizes iliotibial tract

• Gluteus medius and gluteus minimus: – originate anterior to gluteus maximus– insert on trochanter

Lateral Rotators

• Group of 6 muscles, including:– piriformis– obturator

Adductors • Adductor magnus:

– produces adduction, extension, and flexion

• Adductor brevis:– hip flexion and adduction

• Adductor longus:– hip flexion and adduction

• Pectineus:– hip flexion and adduction

• Gracilis:– hip flexion and adduction

Iliopsoas

• 2 hip flexors insert on the same tendon:

• psoas major • iliacus

Summary: Muscles that Move the Thigh

Table 11–16 (1 of 2)

Summary: Muscles that Move the Thigh

Table 11–16 (2 of 2)

Muscles that Move the Leg

Figure 11–20a


Figure 11–20b, c


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

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

Flexors of the Knee

• Biceps femoris- Hamstrings• Semimembranosus- “• Semitendinosus- “• Sartorius:

– originates superior to the acetabulum

• Popliteus:– rotates the tibia to unlock the knee

Extensors of the Knee

• 4 muscles of the quadriceps femoris: – 3 vastus muscles– rectus femoris muscle

Summary: Muscles that Move the Leg

Table 11–17 (1 of 2)

Summary: Muscles that Move the Leg

Table 11–17 (2 of 2)

Muscles that Move the Foot and Toes

Figure 11–21a, b


Figure 11–21c, d


• 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

4 Muscles that Produce Extension at the Ankle

• Gastrocnemius• Soleus• Fibularis• Tibialis posterior+ The Achilles Tendon-

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

Muscles that Produce Flexion at the Ankle

• Tibialis anterior:– opposes the gastrocnemius

Muscles that Produce Flexion at the Toes

• Flexor digitorum longum• Flexor hallucis longus:

– oppose the extensors

Muscles that Produce Extension at the Toes

• Extensor digitorum longum• Extensor hallucis longus• Extensor retinacula:

– fibrous sheaths hold tendons of toes as they cross the ankle

Summary: Muscles that Move the Foot and Toes

Table 11–18

The Intrinsic Muscles of the Foot

Figure 11–22a

The Intrinsic Muscles of the Foot

Figure 11–22b, c

Summary: The Intrinsic Muscles of the Foot

Table 11–19

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

Integration with Other Systems

Figure 11–24

Integration with Other Systems

• Cardiovascular system:– delivers oxygen and fuel– removes carbon dioxide and wastes

• Respiratory system:– responds to oxygen demand of

muscles

• Integumentary system:– disperses heat from muscle activity

• Nervous and endocrine systems:– direct responses of all systems

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

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

Chapter 11: The Muscular System Biol 141 A&P. The Muscular System Consists only of skeletal muscles...

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Transcript of Chapter 11: The Muscular System Biol 141 A&P. The Muscular System Consists only of skeletal muscles...