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 —

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Testing Your Recall — 2, 11-13, 17-20

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True or False – 1 10-2 6-2

I. Introduction & connective tissues of a muscle

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§ Introduction of Muscles

•

600 Human skeletal muscles

•

The study of muscles – M___________ 10-4

§ 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 10-5

§ Connective Tissues of a Muscle

5.

Tendon 4.

Deep fascia 3.

Epi mysium 2.

Peri mysium Muscle fascicle 1.

Endo mysium Muscle fiber 10-6

Connective Tissues of a Muscle

1. Endomysium

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thin areolar tissue around each muscle fiber

–

allows room for ____________________ 2. Perimysium

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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) 10-7

Location of Fascia

• Deep fascia Superficial Fascia

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found between adjacent Deep Fascia muscles; no fat • Superficial fascia ( adipose tissue; hypodermis )

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between skin and muscles Femur Skin 10-8

§ Ways of Muscle Attachments

1. To bone directly--

– –

epimysium is continuous with periosteum of a bone Ex.

– intercostal muscles 2. To bone indirectly--

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epimysium continues as tendon periosteum

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that merges into Ex.-- many including biceps brachii to scapula 3. To fascia or tendon of another muscle- 4. To collagen fibers (dermis)--

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

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Ex.--certain abdominal muscles (Fig. 10.15) 10-9

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II. General anatomy of skeletal muscles and classification of muscles

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§ Anatomy of Skeletal Muscles

• Origin—

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stationary end of a muscle when contracts • Belly--

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thicker, middle region of muscle • Insertion—

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mobile end of muscle

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Detail fig. next slide Biceps brachii 10-12

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§ Muscle types based on fascicle direction-1 10-14

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

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rectus abdominis m., sartorius of the thigh, zygomaticus major 3. Convergent muscle ; fan-shaped, broad at origin and tapering to a narrower insertion

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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.)

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Multipennate--like feathers with their quills on a single point; deltoid (shoulder) (Fig.) 5. Circular muscles

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Features: (sphincters) orbicularis oculi (eyelids), orbicularis oris, urethral and anal sphincters

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. 10-22

§ 4 categories of muscles based on actions

3. Antagonist is a muscle that . . .

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opposes the _____________ Moderates the speed or range of the agonist; preventing excessive movement and injury

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Example: Triceps brachii 4. Fixator is a muscle that . . .

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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

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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

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From spinal cord and exit the vertebral column through intervertebral foramina (Fig. 13.1, 8.23b) 10-26

10-27

O

h

O

nce

O

ne

T

akes

T

he

A

natomy

F

inal

V

ery

G

ood

V

acations

Are H

eavenly Olfactory (I) Optic (II) Oculomotor (III) Trochlear (IV) Trigeminal (V) Abducens (VI) Facial (VII) Vestibulocochlear (VIII) Glossopharyngeal (IX) Vagus (X) Accessory (XI) Hypoglossal (XII)

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Figure 13.1b; posterior view

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Figure 8.23b

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• • •

§ How Muscles are Named

Terminologia Anatomica

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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)

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Explore the location, origin, insertion and innervation of 160 skeletal muscles

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use tabular information in this chapter.

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Increase your retention

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examining models and atlases

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palpating yourself (atlas B)

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observe an articulated skeleton

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say the names aloud and check your pronunciation 10-32

Quadriceps femoris

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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

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internal intercostal muscles Contraction of first 2 produces inspiration Expiration-- ??

Contraction of last produces-- forced expiration Normal expiration requires little muscular activity 10-36

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

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Increases/decreases the vertical dimension of the thorax Central tendon 10-37

2. External/internal Intercostals

• External intercostals

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O- inferior margin of rib above; I superior border of next lower rib

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extend downward and anteriorly from rib to rib

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pull ribcage up/down (when contract) • Internal intercostals

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O- and I- opposite of that in external intercostals

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extend upward and anteriorly from rib to rib

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pull ribcage downward/upward (during forced expiration) 10-38

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 10-39

External intercostal muscles (relaxed) Contraction of external intercostal muscles Elevated rib cage Sternum Elevation of ribs & sternum Increase side-to side and front-to back dimensions of thoracic cavity (X & Y axes) Diaphragm (relaxed) Before inspiration Contractions of external intercostal muscles causes elevation of ribs, which increases side-to-side dimension of thoracic cavity Inspiration Contraction of diaphragm vertical (Z axis) dimension increases in thoracic cavity 10-40

760 759 mm Hg Size of thorax



on contraction of inspiratory muscles Size of lungs



as they are stretched to fill the expanded thorax During inspiration 10-41

Accessory muscles of inspiration 1. Sternocleidomastoid 2. Scalenus 1. External intercostal muscles 2. Diaphragm Major muscles of inspiration 4. Muscles in breathing Internal intercostal muscles Muscles of active expiration Abdominal muscles 10-42

Relaxation of external intercostal muscles Contraction of internal intercostal muscles Contraction of internal intercostal muscles flattens ribs and sternum, further reducing side-to-side and front-to-back dimensions of thoracic cavity Relaxation of diaphragm Passive expiration Return of diaphragm, ribs, and sternum to resting position on relaxation of inspiratory muscles restores thoracic cavity to preinspiratory size Contraction of abdominal muscles Position of relaxed abdominal muscles Contractions of abdominal muscles cause diaphragm to be pushed upward, further reducing vertical dimension of thoracic cavity Active expiration 10-43

§ Muscles of the Abdomen

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4 Pairs of sheetlike muscles

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external oblique (most superficial)

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internal oblique

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transverse abdominal (the first three: from superficial to deep)

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rectus abdominal

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Functions

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support the viscera

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stabilize the vertebral column

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help in respiration, urination, defecation and childbirth 10-44

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

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

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Fibers downward and anteriorly

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The aponeurosis of external oblique forms inguinal ligament

•

Rectus abdominal

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vertical, straplike from pubis (O) to xiphoid process (I)

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3 tendinous intersections rectus sheath encloses rectus abdominal

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They meet at the median line called linea alba External oblique Rectus abdominis 10-46

Internal oblique & transverse abdominis

•

Internal oblique

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Fibers pass upward and anteriorly

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Perpendicular to those of external oblique

•

Transverse abdominal

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Horizontal fiber orientation

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Deepest layer Internal oblique Transverse abdominis 10-47