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4/27/2015

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Chapter 10

The Muscular System

AP1-LectureGoodwin College

Introduction

• In this chapter we will cover:

– Structural and functional organization of muscles

– Muscles of the head and neck

– Muscles of the trunk

– Muscles acting on the shoulder and upper limb

– Muscles acting on the hip and lower limb

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The Functions of Muscles Myology—the study of the muscular system• About 600 human skeletal muscles

• Constitute about half of our body weight

• Three kinds of muscle tissue : Skeletal, cardiac, smooth

Functions:

• Movement– Move from place to place, movement of body parts and body

contents in breathing, circulation, feeding and digestion, defecation, urination, and childbirth

– Role in communication: speech, writing, nonverbal communications

• Stability– Maintain posture by preventing unwanted movements– Antigravity muscles: resist pull of gravity and prevent us from falling

or slumping over– Stabilize joints

10-3

The Functions of Muscles

• Control of openings and passageways– Sphincters: internal muscular rings that control the movement of food, bile, blood, and other materials within the body

• Heat production by skeletal muscles– As much as 85% of our body heat

• Glycemic control– Regulation of blood glucose concentrations within its normal range

• Specialized for one major purpose

– Converting the chemical energy in ATP into the mechanical energy of motion

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Connective Tissues of a MuscleCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Skeletalmuscle

Perimysium

Endomysium

(a)

Perimysium

Epimysium

Nerve

Blood vessels

Muscle fiber

Tendon

Fascia

Muscle fascicle

10-5

Figure 10.1a

Connective Tissues and Fascicles• Endomysium

– Thin sleeve of loose connective tissue surrounding each muscle fiber– Allows room for capillaries and nerve fibers to reach each muscle fiber– Provides extracellular chemical environment for the muscle fiber and its associated

nerve ending

• Perimysium– Slightly thicker layer of connective tissue– Fascicles: bundles of muscle fibers wrapped in perimysium– Carry larger nerves and blood vessels, and stretch receptors

• Epimysium– Fibrous sheath surrounding the entire muscle– Outer surface grades into the fascia– Inner surface sends projections between fascicles to form perimysium

• Fascia– Sheet of connective tissue that separates neighboring muscles or muscle groups from

each other and the subcutaneous tissue

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Fascicles and Muscle Shapes

Figure 10.2

• Strength of a muscle and the direction of its pull aredetermined partly by the orientation of its fascicles

Fusiform

Parallel

TriangularUnipennate

Bipennate

Multipennate

Circular

Biceps brachii

Rectus abdominis

Pectoralis majorPalmar interosseous

Rectus femoris

Deltoid

Orbicularis oculi

Tendon

Tendon

Belly

Copyright © The McGraw‐Hill Companies, Inc. Permission required for reproduction or display.

10-7

Muscle Compartments

• A group of functionally related muscles enclosed and separated from others by connective tissue fascia

• Contains nerves, blood vessels that supply the muscle group

– Thoracic, abdominal walls, pelvic floor, limbs

• Intermuscular septa separate one compartment from another10-8

Figure 10.3

Anterior

Lateral Medial

Posterior

Key

Posterior compartment,superficial layer

Posterior compartment,deep layer

Lateral compartment

Anterior compartmentSubcutaneousfat

Fasciae

Intermuscularsepta

Artery, veins,and nerve

Interosseousmembrane

FibulaTibia


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Muscle Attachments

• Indirect attachment to bone

– Tendons bridge the gap between muscle ends and bony attachment

• Collagen fibers of the endo‐, peri‐, and epimysium continue into the tendon

• From there into the periosteum and the matrix of bone

• Biceps brachii, Achilles tendon

• Aponeurosis—tendon is a broad, flat sheet (palmar aponeurosis)

• Retinaculum—connective tissue band that tendons from separate muscles pass under

• Direct (fleshy) attachment to bone

– Little separation between muscle and bone

– Muscle seems to immerge directly from bone

• Margins of brachialis, lateral head of triceps brachii

10-9

Muscle Origins and Insertions

• Origin

– Bony attachment at stationary end of muscle

• Belly

– Thicker, middle region of muscle between origin and insertion

• Insertion

– Bony attachment to mobile end of muscle

Exception: Facial muscles insert in the skin

Distal tendon of the biceps brachii inserts on the fascia of Figure 10.4

Scapula

Bellies

Radius

Insertion

Humerus

UlnaInsertion

Origins Origins

Long head

Extensors:

Lateral head

Flexors:Biceps brachii

Brachialis


Triceps brachii

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Functional Groups of Muscles

Action—The effects produced by a muscle

– To produce or prevent movement

Four categories depending on action

A) Prime mover (agonist) : Muscle that produces most of force during a joint action. Ex. In flexing elbow, prime mover is brachialis

B) Synergist:Muscle that aids the prime mover,

Stabilizes the nearby joint,

Modifies the direction of movement

Ex. Bicep brachii acts as synergist of brachialis to flex elbow10-11

Functional Groups of Muscles

C) Antagonist: opposes the prime mover

• Relaxes to give prime mover control over an action

• Preventing excessive movement and injury

• Antagonistic pairs—muscles that act on opposite sides of a joint

• Ex. In flexion of elbow brachialis is prime mover and triceps is the antagonist

D) Fixator:muscle that prevents movement of bone

Ex. Rombiods muscles attach (fix) the scapula to the vertebral column

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Examples of Functional Groups of Muscles

• Prime mover—brachialis

• Synergist—biceps brachii

• Antagonist—triceps brachii

• Fixator—muscle that holds scapula firmly in place– Rhomboids

Figure 10.4

Scapula

Bellies

Radius

Insertion

Humerus

UlnaInsertion

Origins Origins

Extensors:

Lateral head

Flexors:Biceps brachii

Brachialis


Long headTriceps brachii

10-13

Intrinsic and Extrinsic Muscles

• Intrinsic muscles—entirely contained within a region, such as the hand– Both its origin

and insertion there

• Extrinsic muscles—act on a designated region, but has its origin elsewhere– Fingers: extrinsic

muscles in the forearm

Figure 10.28b

Figure 10.31a

(b) Intermediate flexor

Flexordigitorumsuperficialis

Flexorpollicis longus

Flexordigitorumsuperficialistendons

Flexordigitorumprofundustendons

Commonflexortendon

Opponens pollicis

Abductor pollicisbrevis

Flexor pollicisbrevis

Adductorpollicis

Tendon of flexordigitorum superficialis

Tendon of flexordigitorum profundus

Abductor pollicislongus

Palmaris longus

Flexor digitorumsuperficialis

Flexor carpi ulnaris

Flexor retinaculum

Abductor digitiminimi

Flexor digiti

Lumbricals

Opponensdigiti minimi

Tendon sheath

Flexor pollicislongus

Flexor carpiradialis

Tendon of flexorpollicis longus

First dorsalinterosseous

Tendons of:

Tendons of:

(a) Palmar aspect, superficial



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Muscle Innervation

• Innervation of a muscle—refers to the identity of the nerve that stimulates it

– Enables the diagnosis of nerve, spinal cord, and brainstem injuries from their effects on muscle function

• Spinal nerves arise from the spinal cord

– Emerge through intervertebral foramina

– Immediately branch into a posterior and anterior ramus

– Innervate muscles below the neck

– Plexus: weblike network of spinal nerves adjacent to the vertebral column

• Cranial nerves arise from the base of the brain

– Emerge through skull foramina

– Innervate the muscles of the head and neck

– Numbered CN I to CN XII 10-15

Blood Supply

• Muscular system receives about 1.24 L of blood per minute at rest (one‐quarter of the blood pumped by the heart)

• During heavy exercise total cardiac output rises and the muscular system’s share is more than three‐quarters (11.6 L/min)

• Capillaries branch extensively through the endomysium to reach every muscle fiber

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The Muscular System

Figure 10.5b


Figure 10.5a

Semispinalis capitis

Levator scapulae

Rhomboideus minor

Rhomboideus major

Infraspinatus

Internal abdominal oblique

Erector spinae


Extensor digitorum (cut)

Serratus posterior inferior

Serratus anterior

Supraspinatus

Splenius capitis

Gluteus minimus

Lateral rotators

Triceps brachii (cut)

External abdominal oblique

Trapezius

Latissimus dorsi

Extensor carpiradialis longusand brevisExternal abdominaloblique

Iliotibial band

Soleus (cut)

Deltoid (cut)Teres minor

Triceps brachii

Gluteus maximus

Gastrocnemius

Soleus

Calcaneal tendon

(b) Posterior view

Sternocleidomastoid

Occipitalis

Infraspinatus

Fibularis longus

Flexor digitorum longus

Extensor hallucis longus

Tibialis posterior

Gastrocnemius (cut)

Teres major

Adductormagnus

Iliotibial band

Biceps femoris

SemitendinosusSemimembranosus

Gluteus medius

Extensor carpi ulnaris

Extensor digitorum

Deep Superficial

Biceps femoris

Gracilis

Frontalis

Orbicularis oculiMasseter

Orbicularis oris

Trapezius

External abdominaloblique

Pronator quadratus

Gastrocnemius

Soleus

Adductor longus

Rectus abdominis

Serratus anterior

Sternocleidomastoid

Deltoid

Pectoralis major

Biceps brachii

Brachioradialis

Sartorius

Tensorfasciae latae

Rectus femoris

Fibularis longus

Extensor digitorum longus

Tibialis anterior

Zygomaticus major

Vastus lateralis

Gracilis

Vastus intermedius

Adductors

Extensor digitorumlongus

Supinator

Flexor digitorumprofundus

Flexor pollicis longus

Transverse abdominal

Brachialis

Coracobrachialis

Platysma

Flexor carpi radialis

(a) Anterior view

Vastus medialis

Pectoralis minor

Internal abdominaloblique

DeepSuperficial

Vastus lateralis


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Muscles of Facial Expression

• Muscles that insert in the dermis and subcutaneous tissues

• Tense the skin and produce facial expressions

• Innervated by facial nerve (CN VII)

• Paralysis causes face to sag

• Found in scalp, forehead, around the eyes, nose, and mouth, and in the neck

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Main Muscles of Facial Expression

Figure 10.8a

Frontalis

Galea aponeurotica

Orbicularis oculi

Platysma(a) Anterior view

Mentalis (cut)

Orbicularis oris

MasseterZygomaticus minor

Levator labii superioris

Zygomaticus majorRisorius

Depressor anguli oris

Depressor labii inferioris

Nasalis

BuccinatorModiolus

Levator anguli oris

Superficial Deep


10-19

Muscles of Facial Expression

Frontalis (cut)Galea aponeurotica

Orbicularis oculi

Sternohyoid

Orbicularis oris

Occipitalis

Omohyoid

Sternothyroid

Sternocleidomastoid

Masseter

Thyrohyoid

Levator labii superioris

Zygomaticus minor

Zygomaticus major

Depressor labiiinferioris

Buccinator

Nasalis

Mentalis

Levator scapulae

(b) Lateral view

Temporalis


Figure 10.8b 10-20

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Muscles of Chewing and Swallowing

• Four pairs of muscles produce the biting and chewing movements of the mandible– Depression: to open mouth

– Elevation: biting and grinding

– Protraction: incisors can cut

– Retraction: make rear teeth meet

– Lateral and medial excursion: grind food

• Temporalis, masseter, medial pterygoid, and lateral pterygoid

• Innervated by mandibular nerve, a branch of the trigeminal (CN V)

Figure 10.10a,b

Temporalis

Orbicularis oris

Masseter (cut)

(a) Lateral view

Buccinator


(b) Posterior view

Medial pterygoid muscle

Medial pterygoid plate

Lateral pterygoid plate

Interior of oral cavity

Lateral pterygoid muscle

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Muscles of Chewing and Swallowing• Hyoid muscles—suprahyoid group

• Aspects of chewing, swallowing, and vocalizing

• Eight pairs of hyoid muscles associated with hyoid bone

• Digastric—opens mouth widely

• Geniohyoid—depresses mandible

• Mylohyoid—elevates floor of mouth at beginning of swallowing

• Stylohyoid—elevates hyoid

Figure 10.11a

Levator scapulae

Sternocleidomastoid

Digastric:Anterior bellyPosterior belly

StylohyoidMylohyoid

SternohyoidOmohyoid:

Suprahyoidgroup

Infrahyoidgroup

(a) Anterior view

Hyoid bone

Common carotid artery

Internal jugular vein

Clavicle

Thyrohyoid

Superior bellyInferior belly

Superficial Deep

Infrahyoidgroup

Sternothyroid


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• Hyoid muscles—infrahyoid group

• Fix hyoid bone from below, allowing suprahyoid muscles to open mouth

• Omohyoid—depresses hyoid after elevation

• Sternohyoid—depresses hyoid after elevation

• Thyrohyoid—depresses hyoid and elevates larynx

• Sternothyroid—depresses larynx after elevation

Figure 10.11b 10-23

Stylohyoid

Hyoglossus

Mylohyoid

Digastric(anterior belly)

Hyoid bone

Thyrohyoid

Omohyoid(superior belly)

Sternothyroid

Sternohyoid

(b) Lateral view

Digastric (posterior belly)

Splenius capitis

Inferior pharyngeal constrictor

Sternocleidomastoid

Trapezius

Levator scapulae

Scalenes

Omohyoid (inferior belly)



• Pharynx: three pairs pharyngeal constrictors

– Encircle pharynx forming a muscular funnel

– During swallowing, drive food into the esophagus

Figure 10.9

Genioglossus

Styloglossus

Palatoglossus

Posterior belly of digastric (cut)

Stylohyoid

Superior pharyngeal constrictor (cut)

Middle pharyngeal constrictor

Inferior pharyngeal constrictor

Hyoglossus

Hyoid bone

Styloid process

Mastoid process

Mylohyoid (cut)

Geniohyoid

Esophagus

Inferior longitudinalmuscle of tongue

Larynx


Trachea

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Muscles Acting on the Head

• Originate on the vertebral column, thoracic cage, and pectoral girdle

• Insert on the cranial bones

• Actions

– Flexion (tipping head forward)

– Extension (holding the head erect)

– Lateral flexion (tipping head to one side)

– Rotation (turning the head to the left and right)

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Muscles Acting on the Head

• Neck flexors

– Sternocleidomastoid (whip lash)

• Neck extensors

– Trapezius• May cause contralateral

movement: movement of the head toward the opposite side

• May cause ipsilateralmovement: movement of the head toward the same side

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Figure 10.12


Superior nuchal line


Sternocleidomastoid

Longissimus capitisLongissimus cervicis

Trapezius

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Muscles of the Trunk/ Functional Groups

• Three functional groups

– Muscles of respiration

– Muscles that support abdominal wall and pelvic floor

– Movement of vertebral column

• Breathing requires the use of muscles enclosing thoracic cavity

– Diaphragm, external intercostal, internal intercostal, and innermost intercostal muscles

• Other muscles of chest and abdomen that contribute to breathing

– Sternocleidomastoid, scalenes of neck

– Pectoralis major and serratus anterior of chest

– Latissimus dorsi of back

– Abdominal muscles: internal and external obliques, and transverse abdominis

– Some analmuscles10-27

Muscles of Respiration

• External intercostals

– Elevate ribs

– Expand thoracic cavity

– Create partial vacuum causing inflow of air

• Internal intercostals

– Depresses and retracts ribs

– Compresses thoracic cavity

– Expelling air

• Diaphragm—muscular dome between thoracic and abdominal cavities

Figure 10.13a

Externalintercostals

Internalintercostals

(a) Lateral view of intercostal muscles


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Muscles of the Anterior Abdominal Wall

• Internal abdominal oblique

– Intermediate layer of lateral abdominal muscles

– Unilateral contraction causes ipsilateral rotation of waist

– Aponeurosis

• Tendons of oblique and transverse muscles

• Broad, fibrous sheets

Subclavius

Pectoralis minor (cut)

Internal intercostals

External intercostals

Rectus abdominis (cut)

External abdominaloblique (cut)

Internal abdominaloblique (cut)

Transverse abdominal (cut)

Posterior wall of rectus sheath(rectus abdominis removed)


Inguinal ligament

Rectus sheath

Serratus anterior

Pectoralis minor

(b) Deep


Figure 10.15b 10-29


• Transverse abdominal

– Deepest of lateral abdominal muscles

– Horizontal fibers

– Contributes to movements of vertebral column

Subclavius










Inguinal ligament

Rectus sheath

Serratus anterior

Pectoralis minor

(b) Deep


Figure 10.15b 10-30

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• Rectus abdominis– Flexes lumbar region of vertebral column

– Produces forward bending at the waist

– Three transverse tendinous intersections divide rectus abdominis into segments, sometimes called a “six pack”

Figure 10.15a

Pectoralis major

Tendinousintersections

Linea alba

Latissimus dorsi

Rectus abdominis

Inguinal ligament

Rectus sheath (cut edges)

Serratus anterior

Aponeurosis ofexternal abdominaloblique

Umbilicus

Linea semilunaris

Transverse abdominal



Rectus sheath

(a) Superficial


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Major Muscles of Back

Superficial musclesExtend, rotate,

and laterally flex vertebral column

• Most prominent: Latissimus dorsiand Trapezius

Figure 10.17


Sternocleidomastoid

Deltoid

Latissimusdorsi

Thoracolumbarfascia


Levator scapulae

Rhomboideus minor

Rhomboideus major

Infraspinatus

Teres minor


Gluteus maximus

Gluteus medius Gluteus minimus

Lateral rotators

Serratus posteriorinferior

Serratus anterior

Supraspinatus

Erector spinae

Splenius capitis

Teres major


Trapezius

Superficial Deep


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Muscles of the Pelvic Floor

• Three layers of muscles and fasciae that span pelvic outlet– Penetrated by anal canal, urethra, and vagina

• Perineum—diamond‐shaped region between the thighs – Bordered by four bony landmarks

• Pubic symphysis anteriorly• Coccyx posteriorly• Ischial tuberosities laterally

– Urogenital triangle: anterior half of perineum– Anal triangle: posterior half of perineum

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Aponeurosis of externalabdominal obliquemuscle

Inguinal canal

External inguinal ring

Herniated loop ofsmall intestineUpper scrotum

Hernias

• Hernia—any condition in which the viscera protrudes through a weak point in the muscular wall of the abdominopelvic cavity

• Inguinal hernia

– Most common type of hernia (rarein women)

– Viscera enter inguinal canal or even the scrotum

• Hiatal hernia

– Stomach protrudes through diaphragm into thorax

– Overweight people over 40

• Umbilical hernia

– Viscera protrude through the navel10-34

Figure 10.21

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Muscles Acting on the Shoulder and Upper Limb

• Compartments—spaces in which muscles are organized and are separated by fibrous connective tissue sheets (fasciae)

– Each compartment contains one or more functionally related muscles along with their nerve and blood supplies

• Muscles of upper limbs divided into anterior and posterior compartments

• Muscles of lower limbs divided into anterior, posterior, medial, and lateral compartments

• Intermuscular septa (thick fascia) separates compartments

• Compartment syndrome—one of the muscles or blood vessels in a compartment is injured

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Compartment Syndrome

• Fasciae of arms and legs enclose muscle compartments very snugly

• If a blood vessel in a compartment is damaged, blood and tissue fluid accumulate in the compartment

• Fasciae prevent compartment from expanding with increasing pressure

• Compartment syndrome—mounting pressure on the muscles, nerves, and blood vessels triggers a sequence of degenerative events

– Blood flow to compartment is obstructed by pressure– If ischemia (poor blood flow) persists for more than 2 to 4 hours, nerves

begin to die

– After 6 hours, muscles begin to die

• Nerves can regenerate after pressure relieved, but muscle damage is permanent

• Myoglobin in urine indicates compartment syndrome

• Treatment: immobilization of limb and fasciotomy (incision to relieve compartment pressure)

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Muscles Acting on the Shoulder and Upper Limb

• Upper limb is used for a broad range of powerful and subtle actions

– Climbing, grasping, throwing, writing, playing musical instruments, and manipulating small objects

• Muscles that act on the scapula

• Muscles that act on the humerus and shoulder joint

• Muscles that act on the forearm and elbow joint

• Intrinsic—forearm

• Extrinsic—hand

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Muscles Acting on the Scapula

ProtractionPectoralis minorSerratus anterior

RetractionRhomboideus majorRhomboideus minor

Medial rotationLevator scapulaeRhomboideus majorRhomboideus minor

Lateral rotation

Serratus anterior

ElevationLevator scapulae

Rhomboideus majorRhomboideus minor

Depression

Serratus anterior

Trapezius (superior part)Trapezius (superior part)

Trapezius (inferior part)

Trapezius

Figure 10.22


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Muscles Acting on the Shoulder

• Pectoralis minor

– Ribs 3–5 to coracoid process of scapula

– Draws scapula laterally

• Serratus anterior

– Rbs 1–9 to medial border of scapula

– Abducts and rotates or depresses scapula

Subclavius





Inguinal ligament

Rectus sheath

Serratus anterior

Pectoralis minor

(b) Deep







Figure 10.15b 10-39

• Anterior group of muscles of pectoral girdle


• Four muscles of posterior group

– Trapezius: superficial

– Levator scapulae, rhomboideus minor, and rhomboideus major: deep

• Trapezius

– Stabilizes scapula and shoulder

– Elevates and depresses shoulder apex

Figure 10.17


Sternocleidomastoid

Deltoid

Levator scapulae

Rhomboideus minor

Rhomboideus major

Infraspinatus

Gluteus maximus


Lateral rotators

Serratus anterior

Supraspinatus

Erector spinae

Splenius capitis

Superficial Deep

Trapezius

Latissimusdorsi

External abdominalobliqueThoracolumbarfascia

Teres minor

Teres major





10-40

• Posterior group of muscles of pectoral girdle

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• Levator scapulae

– Elevates scapula

– Flexes neck laterally

• Rhomboideus minor

– Retracts scapula and braces shoulder

• Rhomboideus major

– Same as rhomboideus minor

Muscles Acting on the Arm

• Nine muscles cross the shoulder joint and insert on humerus

• Two are axial muscles because they originate on axial skeleton– Pectoralis major: flexes, adducts, and medially rotates humerus

– Latissimus dorsi: adducts and medially rotates humerus

Figure 10.23a Figure 10.23b

Clavicle

Deltoid

Sternum

Pectoralis major

CoracobrachialisLateral head

Long head

Medial head

Biceps brachii

Brachialis

Brachioradialis

Triceps brachii:

(a) Anterior view


(b) Posterior view

Supraspinatus

Spine of scapula

Infraspinatus

Lateral headLong head

Latissimus dorsi

Humerus

Greater tubercleof humerus

Teres minor

Teres major

Triceps brachii:


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Figure 10.17


Sternocleidomastoid

Deltoid

Levator scapulae

Rhomboideus minor

Rhomboideus major

Infraspinatus

Gluteus maximus


Lateral rotators

Serratus anterior

Supraspinatus

Erector spinae

Splenius capitis

Superficial Deep

Trapezius

Latissimus dorsi


Teres minor

Teres major


External abdominalobliqueInternal abdominaloblique


10-43

Posterior scapular muscles

• Seven scapular muscles

• Originate on scapula

– Deltoid• Rotates and abducts arm

• Intramuscular injection site

– Teres major • Extension and medial rotation of humerus

– Coracobrachialis• Flexes and medially rotates arm

– Remaining four form the rotator cuff that reinforce the shoulder joint


Figure 10.23b

Figure 10.23a

Clavicle

Deltoid

Sternum

Pectoralis major

CoracobrachialisLateral headLong head

Medial head

Biceps brachii

Brachialis

Brachioradialis

Triceps brachii:

(a) Anterior view


(b) Posterior view

Supraspinatus

Spine of scapula

Infraspinatus


Latissimus dorsi

Humerus


Teres minor

Teres major

Triceps brachii:


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Anterior View of Cadaver Chest

Figure 10.24a

Deltoid

Pectoralis major

Biceps brachii:

Long head

Short head

Serratus anterior

Externalabdominaloblique

(a) Anterior view


© The McGraw-Hill Companies, Inc./Rebecca Gray, photographer/Don Kincaid, dissections

10-45

Back Muscles of Cadaver

Figure 10.24b

(b) Posterior view

Deltoid

Infraspinatus

Latissimus dorsi

Levator scapulaeRhomboideus minor

Rhomboideus major

Teres major

Triceps brachii:

Teres minor



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• Rotator cuff muscles

• Tendons of the remaining four scapular muscles form the rotator cuff

• Acronym “SITS muscles”

– Supraspinatus

– Infraspinatus

– Teres minor

– Subscapularis

• Holds head of humerus into glenoid cavity

• Supraspinatus tendon most easily damaged

10-47

Rotator Cuff Muscles

Figure 10.25

Acromion

Inferior angle

Clavicle

Infraspinatus

Subscapularis

Glenoid cavity

Supraspinatus

Anterior Posterior

Rotator cuff (SITS)muscles:

Teres minor

Coracoidprocess


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Muscles Acting on the Forearm

• Elbow and forearm capable of flexion, extension, pronation, and supination

– Carried out by muscles in both brachium (arm) and antebrachium (forearm)

• Muscles with bellies in the arm (brachium)

– Principal elbow flexors: anterior compartment

• Brachialis and biceps brachii– Brachialis produces 50% more power than biceps brachii

– Brachialis is prime mover of elbow flexion

– Principal elbow extensor: posterior compartment

• Triceps brachii– Prime mover of elbow extension

10-49


• Muscles with bellies in the forearm (antebrachium)

• Most forearm muscles act on the hand and wrist

– Brachioradialis: flexes elbow

– Anconeus: extends elbow

– Pronator quadratus: prime mover in forearm pronation

– Pronator teres: assists pronator quadratus in pronation

– Supinator: supinates the forearm

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• Principal flexor

– Brachialis

• Synergistic flexors

– Biceps brachii

– Brachioradialis

• Principal extensor

– Triceps brachii

Figure 10.23b

Figure 10.23a

Clavicle

Deltoid

Sternum

Pectoralis major

CoracobrachialisLateral headLong headMedial head

Biceps brachii

Brachialis

Brachioradialis

Triceps brachii:

(a) Anterior view


(b) Posterior view

Supraspinatus

Spine of scapula

Infraspinatus


Latissimus dorsi

Humerus


Teres minor

Teres major

Triceps brachii:


Biceps brachii:

Long head

Short head

(c) Anterior view


Figure 10.23c

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• Supination– Supinatormuscle– Palm facing anteriorly or

superiorly

• Pronation– Pronator quadratus and pronator

teres– Palm faces posteriorly or inferiorly

Figure 10.26a Figure 10.26c


Medial epicondyle

Lateral epicondyle

Ulna

Pronator quadratus

Pronator teres

Supinator

Radius

Radius

(a) Supination

Ulna

Bursa

Bicepsbrachii

Supinator

(b) Muscle actionsin supination


Medial epicondyle

Lateral epicondyle

Ulna

Pronator quadratus

Pronator teres

Supinator

Radius

Radius

(c) Pronation

Ulna

Bursa

Bicepsbrachii

Supinator

(b) Muscle actionsin supination

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Muscles Acting on the Wrist and Hand

• Anterior group

• Extrinsic muscles of the forearm

• Intrinsic muscles in the hand itself

• Extrinsic muscle actions

– Flexion and extension of wrist and digits

– Radial and ulnar flexion

– Finger abduction and adduction

– Thumb opposition

Figure 10.28a,b,c


(c) Deep flexors(b) Intermediate flexor(a) Superficial flexors

Flexordigitorumsuperficialis

Flexordigitorumprofundus

Supinator

Flexorpollicislongus

Biceps brachii

Brachialis

Pronator teres

Brachioradialis

Flexor carpi radialis

Palmaris longus


Extensor carpi radialislongus and brevis

Triceps brachii

Common flexor tendon

Aponeurosis of bicepsbrachii


Interosseousmembrane

Flexorpollicis longus



Common flexortendon

Palmaraponeurosis



Flexorretinaculum

Anterior view

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• Anterior (flexor) compartment—superficial layer

– Flexor carpi radialis

– Flexor carpi ulnaris

– Flexor digitorum superficialis

– Palmaris longus

• Anterior (flexor) compartment—deep layer

– Flexor digitorum profundus

– Flexor pollicis longus


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• Posterior group

• Extension of wrist and fingers, adduct/abduct wrist

• Extension and abduction of thumb (pollicis)

• Brevismeans “short,” ulnaris indicates “on ulna side of forearm”Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Anconeus

Supinator


Extensor pollicislongus

Extensor pollicisbrevis

Extensor indicis

Olecranon

Tendons of extensordigitorum

(a) Superficial extensors (b) Deep extensors

Posterior view

Extensor carpiulnaris

Anconeus

Triceps brachii

Flexor carpiulnaris

Extensor digitiminimi

Tendon ofextensor indicis

Extensor carpiradialis longus

Extensor carpiradialis brevis

Extensor digitorum


Extensor pollicisbrevis

Extensor pollicislongus

Brachioradialis

Tendons of extensorcarpi radialis longusand brevis

Figure 10.29a,b

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• Posterior (extensor) compartment—superficial layer

– Extensor carpi radialis longus

– Extensor carpi radialis brevis

– Extensor digitorum

– Extensor carpi ulnaris

• Posterior (extensor) compartment—deep layer

– Abductor pollicis longus

– Extensor pollicis brevis

– Extensor pollicis longus

– Extensor indicis

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Carpal Tunnel Syndrome

• Prolonged, repetitive motions of wrist and fingers can cause tissues in the carpal tunnel to become inflamed, swollen, or fibrotic

– Puts pressure on the median nerve of the wrist that passes through the carpal tunnel along with the flexor tendons

– Tingling and muscular weakness in the palm and medial side of the hand

– Pain may radiate to arm and shoulder

– Treatment: anti‐inflammatory drugs, immobilization of the wrist, and sometimes surgery to remove part or all of flexor retinaculum

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Carpal Tunnel Syndrome

Repetitive motions cause inflammation and pressure on median

nerve

Figure 10.31a

Figure 10.31b


Opponens pollicis



Adductorpollicis

Tendon of flexordigitorum superficialis

Tendon of flexordigitorum profundus

Palmaris longus


Flexor retinaculum


Flexor digitiminimi brevis

Lumbricals


Tendon sheath

Flexor pollicislongus

Flexor carpiradialis

Tendon of flexorpollicis longus

First dorsalinterosseous

Flexor carpi ulnarisAbductor pollicis longus

(a) Palmar aspect, superficial

Tendons of:Tendons of:

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Tendon of extensorpollicis brevis



Adductorpollicis

Tendon of flexor carpi radialis


Pisiform bone




Lumbrical

Tendon of flexordigitorumsuperficialis

(b) Palmar dissection, superficial

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Muscles Acting on the Hip and Femur

• Lateral and posterior muscles of the hip– Tensor fasciae latae

• Extends knee, laterally rotates knee

– Gluteus maximus• Forms mass of the buttock

• Prime hip extensor

• Provides most of lift when you climb stairs

– Gluteus medius andminimus

• Abduct and medially rotate thigh

Figure 10.33


Gluteusminimus

Quadratusfemoris

Piriformis

GemellussuperiorObturatorinternus

Gemellusinferior

Sacrum

Gluteusmedius

Gluteusmaximus

Coccyx

Ischialtuberosity

Iliac crest

Obturatorexternus

Lateral rotators:

Superficial Deep

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Muscles Acting on the Hip and Femur

• Medial (adductor) compartment of thigh

• Five muscles act as primary adductors of the thigh– Adductor brevis

– Adductor longus

– Adductor magnus

– Gracilis

– Pectineus

Figure 10.32


Iliopsoas:IliacusPsoasmajor

Adductorlongus

Adductorbrevis

Pectineus

Gracilis

Insertion ofgracilis ontibia

Piriformis

Obturatorexternus

Adductormagnus

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Muscles Acting on the Knee and Leg

• Anterior (extensor) compartment of the thigh– Contains large quadriceps femorismuscle

• Prime mover of knee extension

• Most powerful muscle in the body

• Has four heads—rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius

– All converge on single quadriceps (patellar) tendon

– Extends to patella

– Then continues as patellar ligament

– Inserts on tibial tuberosity

– Sartorius: longest muscle in the body• “Tailor’s muscle”

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Anterior Thigh Cadaver Muscles

Figure 10.34


Tensor fasciae latae

Iliopsoas

Sartorius

Iliotibial band

Quadriceps femoris:Rectus femorisVastus lateralisVastus medialis

Quadriceps tendon

Patella

Femoral vein

Femoral artery

Pectineus

Adductor longus

Gracilis

Lateral


Medial

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Figure 10.35a,b


Iliac crest

Iliopsoas:Iliacus

Psoas major

Anterior superioriliac spine

Iliotibial band

(a) Superficial (b) Deep

Sartorius

Quadriceps femoris:

Rectus femoris

Quadricepsfemoris tendont

Patellarligament

Adductor magnus

GracilisAdductor longus

Pectineus

Medial compartment:

L5

Adductor brevis

Anterior compartment:

Tensor fasciaelatae

Vastusintermedius

Patella

Vastus lateralis

Vastus medialis

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• Posterior (flexor) compartment of the thigh– Contains hamstring muscles

– From lateral to medial:

Biceps femoris

Semitendinosus

Semimembranosus

Figure 10.36


Gluteus medius

Gluteus maximus

Iliotibial band

Short head

Biceps femoris

Hamstring group:

Semitendinosus

Semimembranosus

Adductor magnus

Gracilis

Vastus lateralis

Long head

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Muscles Acting on the Foot

• Posterior compartment—three muscles of the superficial group

– Gastrocnemius: plantar flexes foot, flexes knee

– Soleus: plantar flexes foot

• Triceps surae—collective name for gastrocnemius and soleus

– Inserts on calcaneus by way of the calcaneal (Achilles) tendon

– Strongest tendon in the body


Gastrocnemius:

Heads ofgastrocnemius(cut)

Calcaneal tendon

Calcaneus

Medial headLateral head

Popliteus

Flexordigitorumlongus

Plantaris

Soleus

Flexorhallucislongus

Tendon ofplantaris

Fibularisbrevis

Fibularislongus

Fibularislongus

Gastrocnemius(cut)

Tendon ofgastrocnemius

(a) (b)

Figure 10.39a,b

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Muscles Acting on the Foot

• Posterior compartment—four muscles in the deep group

– Flexor digitorum longus: flexes phalanges

– Flexor hallucis longus: flexes great toe

– Tibialis posterior: inverts foot

– Popliteus: acts on knee


Calcaneal tendon(cut)

Calcaneus(a)

(b) (c)

(d)

Flexor digitorumlongus

Flexordigitorumlongus

Flexor hallucislongus

Flexorhallucislongus

Popliteus

Popliteus

Plantaris (cut)

Soleus (cut)

Fibula

Fibularislongus

Fibularisbrevis

Gastrocne-mius (cut)

Plantar surfaceof the foot

Tibialisposterior

Tibialisposterior

Figure 10.40

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Intrinsic Muscles of Foot

• Four ventral muscle layers

• Support for arches– Abduct and

adduct the toes

– Flex the toes

• One dorsal muscle– Extensor

digitorumbrevisextends toes

Figure 10.42a–e

Dorsal view

(a) Layer 1, plantar view (b) Layer 2, plantar view

Abductor hallucis

Calcaneus

Lumbricals

Quadratus plantae

(c) Layer 3, plantar view (d) Layer 4, plantar view (e) Layer 4, dorsal view

Adductor hallucis

Flexor hallucis brevis

Abductor hallucis (cut)



Flexor digitorumbrevis

Plantar aponeurosis(cut)

Flexor digitorumbrevis (cut)

Flexor hallucislongus tendon

Flexor digitorumlongus tendonAbductor hallucis(cut)

Flexor hallucislongus tendon (cut)

Flexor digitorumlongus tendon (cut)

Plantarinterosseous

Dorsalinterosseous



Quadratus plantae(cut)

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Common Athletic Injuries

• Muscles and tendons are vulnerable to sudden and intense stress

• Proper conditioning and warm‐up needed

• Common injuries include:– Compartment syndrome

– Shinsplints

– Pulled hamstrings

– Tennis elbow

– Pulled groin

– Rotator cuff injury

• Treat with rest, ice, compression, and elevation

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