Chapter 10—The Muscular System

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Ch. 10 Muscular system-- Study Guide

1. Critically read Chapter 10 pp. 320-327. Also read Tables 10.4 and 10.5 (pp. 339-343)

2. Comprehend Terminology (those in bold in the textbook) within the reading scope above

3. Study-- Figure questions, Think About It questions, and Before You Go On (section-ending) questions (within the reading scope above) . Before You Go On Questions 1-6 (on p. 325) and Questions 11-12 (on p. 349).

4. Do end-of-chapter questions—– Testing Your Recall— 2, 11-13, 17-20– True or False– 1

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I. Introduction & connective tissues of a muscle

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§ Introduction of Muscles

• 600 Human skeletal muscles

• The study of muscles– M___________

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§ The Functions of Muscles

1. Movement of body parts and body contents– Examples

2. Maintain posture and prevent unwanted movement— resist the gravity etc.

3. Communication – 4. Control of openings and passageways–

Examples-- eyelids, __________________5. Heat production– 85% of our body heat is

from skeletal muscle contraction

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§ Connective Tissues of a Muscle

2. Perimysium

3. Epimysium

1. Endomysium

5. Tendon

4. Deep fascia

Muscle fascicle

Muscle fiber

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Connective Tissues of a Muscle1. Endomysium

– thin areolar tissue around each muscle fiber– allows room for ____________________

2. Perimysium– slightly thicker layer of connective tissue– surrounds bundle of cells called a fascicle

3. Epimysium– covers whole muscle belly – blends into CT sheets called fascia (next

slide)

Location of FasciaSuperficial Fascia

Deep Fascia

• Deep fascia– found between

adjacent muscles; no fat

• Superficial fascia (adipose tissue; hypodermis)– between skin and

muscles

Skin

Femur

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§ Ways of Muscle Attachments1. To bone directly--

– epimysium is continuous with periosteum of a bone– Ex.– intercostal muscles

2. To bone indirectly--– epimysium continues as tendon that merges into

periosteum– Ex.-- many including biceps brachii to scapula

3. To fascia or tendon of another muscle--4. To collagen fibers (dermis)--

– Ex.--muscles for facial expression 5. To a broad sheetlike tendon, aponeurosis--

– Ex.--certain abdominal muscles (Fig. 10.15)

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II. General anatomy of skeletal muscles and classification of muscles

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§ Anatomy of Skeletal Muscles

• Origin—– stationary end of a

muscle when contracts

• Belly--– thicker, middle

region of muscle

• Insertion—– mobile end of muscle– Detail fig. next slide

Biceps brachii

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§ Muscle types based on fascicle direction-1

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Skeletal Muscle types —based on fascicle direction-2

1. Fusiform muscles– Features:– biceps brachii m., gastrocnemius of the calf

2. Parallel muscles; long, uniform width, having parallel fascicles– rectus abdominis m., sartorius of the thigh,

zygomaticus major

3. Convergent muscle; fan-shaped, broad at origin and tapering to a narrower insertion – pectoralis major of the chest

Fig. 10.15

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Skeletal Muscle type—based on fascicle direction-3

4. Pennate muscles (feather-shaped)– fascicles insert obliquely on a tendon, like the shaft

of the feather– Unipennate—fascicles approach the tendon from

one side; palmar interosseus (hand) (Fig.)– Bipennate—fascicles approach the tendon from

both sides; rectus femoris (thigh) (Fig.)– Multipennate--like feathers with their quills on a

single point; deltoid (shoulder) (Fig.)

5. Circular muscles (sphincters)– Features:– orbicularis oculi (eyelids), orbicularis oris, urethral

and anal sphincters 10-17

Figure 10.29c

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Fig. 10.35a

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Fig. 10.22a

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III. Action of muscle groups and muscle innervation

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§ 4 categories of muscles based on actions

• Action— movement produced by a muscle

1. Prime mover or agonist– produces . . .– Example: in flexing the elbow, the prime mover

is the brachialis

2. Synergist aids the prime mover– May stabilize the nearby joint– Or modify the direction of movement– Example: works with brachialis, biceps brachii

as a synergist to flex the elbow

* In some textbooks 1 and 2 are opposite.

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§ 4 categories of muscles based on actions

3. Antagonist is a muscle that . . .– opposes the _____________– Moderates the speed or range of the

agonist; preventing excessive movement and injury

– Example: Triceps brachii

4. Fixator is a muscle that . . .– prevents _______________– Elbow flexion– the rhomboids holds the

scapula in place (Fig. 10.17)

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In-class activity Question--Muscle Actions during Elbow Flexion

• ID which specific muscle of the upper arm is responsible for the above action. (based on the text)

• Prime mover (agonist) = ?• Synergist = ?

• Antagonist = ?• Fixator = ?

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§ Skeletal Muscle Innervation• Cranial nerves arising from the brain

– exit the skull through foramina– numbered I to XII (Fig. 14.27)– Innervate muscles of the ______________

• Spinal nerves arising from the spinal cord– Muscles elsewhere are supplied by these

nerves– From spinal cord and exit the vertebral

column through intervertebral foramina (Fig. 13.1, 8.23b)

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Oh Olfactory (I)Once Optic (II)One Oculomotor (III)Takes Trochlear (IV)The Trigeminal (V)Anatomy Abducens (VI)Final Facial (VII)Very Vestibulocochlear (VIII)Good Glossopharyngeal (IX)Vacations Vagus (X)Are Accessory (XI)Heavenly Hypoglossal (XII) 14-28

Figure 13.1b;

posterior view

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Figure 8.23b

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§ How Muscles are Named• Terminologia Anatomica

– system of Latin names developed in 1895– updated since then

• English names for muscles are slight modifications of the Latin names.

• Table 10.1 = terms used to name muscles; Examples:– Major = large (Criteria: ____); pectoralis major– Deltoid = triangular (Criteria: _____); Deltoid– Quadriceps = having 4 heads; quadriceps

femoris etc.

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§ Learning Strategy (start with Fig. 10.4a and b)

• Explore the location, origin, insertion and innervation of 160 skeletal muscles– use tabular information in this chapter.

• Increase your retention– examining models and atlases– palpating yourself (atlas B)– observe an articulated skeleton– say the names aloud and check your

pronunciation

Quadriceps femoris 10-33

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IV. Muscles involved in respiration

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§ Muscles of Respiration• Breathing requires the use of muscles

– Diaphragm (prime mover of inspiration) – external intercostal muscles– internal intercostal muscles

• Contraction of first 2 produces inspiration• Expiration-- ??• Contraction of last produces-- forced

expiration• Normal expiration requires little muscular

activity

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1. Muscles of Respiration- Diaphragm• Muscular dome between

thoracic and abdominal cavities

• Muscle fascicles converge from the margins (Origin) toward a fibrous central tendon (Insertion)

• Contraction flattens it– Increases/decreases the

vertical dimension of the thorax

Central tendon

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2. External/internal Intercostals• External intercostals

– O- inferior margin of rib above; I-

superior border of next lower rib – extend downward and

anteriorly from rib to rib– pull ribcage up/down (when

contract)

• Internal intercostals– O- and I- opposite of that in

external intercostals– extend upward and anteriorly

from rib to rib– pull ribcage downward/upward

(during forced expiration)

3. Breathing-a mechanical step Mechanism of normal quiet inspiration

(expiration are opposite)—• Diaphragm contracts and move downward• External intercostals muscles contract

the ribs elevated Chest volume: intra-alveolar pressure: Air flows inward; why?• Deeper inspiration, 2 neck muscles are

involved

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Externalintercostalmuscles(relaxed)

Contractions of external intercostalmuscles causes elevation of ribs,which increases side-to-sidedimension of thoracic cavity

vertical (Z axis)dimension increases in thoracic cavity

Elevation of ribs & sternumIncrease side-to-side and front-to-back dimensions of thoracic cavity (X & Y axes)

Before inspiration Inspiration

Elevated

rib cage

Contractionof externalintercostalmuscles

Sternum

Diaphragm(relaxed)

Contractionof diaphragm

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759 mm Hg

Size of thorax oncontraction ofinspiratory muscles

Size of lungs as theyare stretched to fillthe expanded thorax

During inspiration

760

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Accessorymuscles ofinspiration

Musclesof activeexpiration

Majormuscles ofinspiration

1. Sternocleidomastoid

2. Scalenus

1. Externalintercostalmuscles

2. Diaphragm

Internalintercostalmuscles

Abdominalmuscles

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4. Muscles in breathing

Relaxationof externalintercostalmuscles

Return of diaphragm, ribs, and sternum to resting position on relaxation of inspiratory muscles restores thoracic cavity to preinspiratory size

Contractions of abdominalmuscles cause diaphragm tobe pushed upward, furtherreducing vertical dimension of thoracic cavity

Contraction of internal intercostal muscles flattens ribs and sternum, further reducingside-to-side and front-to-back dimensions of thoracic cavity

Passive expiration

Active expiration

Contractionof internalintercostalmuscles

Relaxation ofdiaphragm

Contractionof abdominal muscles

Position of relaxedabdominal muscles

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• 4 Pairs of sheetlike muscles– external oblique (most superficial)– internal oblique– transverse abdominal

(the first three: from superficial to deep)– rectus abdominal

• Functions– support the viscera– stabilize the vertebral column– help in respiration, urination, defecation and

childbirth

§ Muscles of the Abdomen

Aponeuroses (broad fibrous sheet-like tendons)– tendons of the oblique and transverse muscles

Rectus abdominis-- wrapped by rectus sheath

Linea alba (“white line”)– at the median line where aponeuroses meet

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External Oblique & Rectus Abdominal• External abdoominal oblique

– Superficial (O-Ribs 5-12; to I-pelvis and linea alba)

– Fibers downward and anteriorly

– The aponeurosis of external oblique forms inguinal ligament

• Rectus abdominal– vertical, straplike from

pubis (O) to xiphoid process (I)

– 3 tendinous intersections– rectus sheath encloses

rectus abdominal– They meet at the median

line called linea alba

External oblique

Rectus abdominis

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Internal oblique & transverse abdominis

• Internal oblique– Fibers pass upward

and anteriorly– Perpendicular to

those of external oblique

• Transverse abdominal– Horizontal fiber

orientation– Deepest layer

Transverse abdominisInternal oblique