Download - Chapter 10 The Muscular System
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Chapter 10The Muscular System
• 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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Structural and Organization of Muscles
• 600 Human skeletal muscles• General structural & functional organization
– functions of muscle– connective tissues of muscle– general anatomy of skeletal muscles– muscle shape and function– coordinated actions of muscle groups – intrinsic and extrinsic muscles– muscle innervation
• Regional descriptions
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The Functions of Muscles
• Movement of body parts and organ contents• Maintain posture and prevent movement• Communication - speech, expression &
writing• Control of openings and passageways• Body heat production
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Connective Tissues of a Muscle
Perimysium
Epimysium
Endomysium
Tendon
Deep fascia
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Connective Tissues of a Muscle• Epimysium
– covers whole muscle belly – blends into connective tissue that separates
muscles• Perimysium
– slightly thicker layer of connective tissue– surrounds a bundle of cells called a fascicle
• Endomysium– thin layer of areolar tissue surrounding each cell– allows room for capillaries and nerve fibers
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Fascicle, c.s.
Fascicles, Perimysium & Endomysium
Endomysium
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Location of Fascia
Superficial Fascia
Deep Fascia
• Deep fascia– found between adjacent muscles
• Superficial fascia (hypodermis)– found between skin and muscles– contains adipose tissue
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Muscle Attachments• Direct (fleshy) attachment to bone
– epimysium is continuous with periosteum– intercostal muscles
• Indirect attachment to bone– epimysium continues as tendon or aponeurosis that
merges into periosteum as perforating fibers– biceps brachii or abdominal muscle
• Attachment to dermis • Stress will tear the tendon before pulling the
tendon loose from either muscle or bone
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Parts of a Skeletal Muscle
• Origin– attachment to stationary end
of muscle• Belly
– thicker, middle region of muscle
• Insertion– attachment to mobile end of
muscle
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Skeletal Muscle Shapes
• Fusiform muscles– thick in middle & tapered at
ends– biceps brachii m.
• Convergent muscle– broad at origin and tapering to
a narrower insertion• Parallel muscles
– parallel fascicles– rectus abdominis m.
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Skeletal Muscle Shapes (2)• Circular muscles
– act as sphincters– ring around body opening– orbicularis oris
• Pennate muscles– fascicles insert obliquely
on a tendon– unipennate, bipennate or
multipennate– palmar interosseus, rectus
femoris & deltoid
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Coordinated Muscle Actions• Prime mover or agonist
– produces most of force• Synergist aids the prime mover
– stabilizes the nearby joint– modifies the direction of movement that occurs
• Antagonist– opposes the prime mover– preventing excessive movement and injury
• Fixator– prevents movement of bone that prime mover is attached to
Example
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Muscle Actions during Elbow Flexion
• Prime mover (agonist) = biceps brachii m.• Synergist = brachialis m.
• Antagonist = triceps brachii m.
• Fixator = muscle that holds scapula firmly in place such as rhomboideus m.
Definitions
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Intrinsic and Extrinsic Muscles
• Intrinsic muscles are contained within a region such as the hand.
• Extrinsic muscles move the fingers but are found outside the region.
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Skeletal Muscle Innervation
• Cranial nerves arising from the brain– exit the skull through foramina– numbered I to XII
• Spinal nerves arising from the spinal cord– exit the vertebral column through
intervertebral foramina
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How Muscles are Named• Nomina 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 musclesdigiti = of a fingerlevator = elevates a body partprofundus = deepestquadriceps = having 4 heads
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Learning Strategy
• Explore the location, origin, insertion and innervation of 160 skeletal muscles using the tabular information in this chapter.
• Increase your retention & understanding by:– examining models and photographic atlases– palpating yourself using the images in Atlas B– observe an articulated skeleton– say the names aloud and check your pronunciation
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The Muscular System
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Muscles of Facial Expression
• Small muscles that insert into the dermis• 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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Occipitofrontalis is found in the scalp. Frontalis m. raises the eyebrows while Occipitalis m. fixes the galea aponeurotica
Muscles of the Scalp and ForeheadFrontalis
Occipitalis
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Corrugator supercilii
Muscles around the Eyes
Nasalis
Orbicularis oculi closes the lips. Corrugator draws the eyebrows together. Procerus pulls down the skin of forehead. Nasalis widens nostrils.
ProcerusOrbicularis Oculi
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• Orbicularis oris encircles mouth & other mm blend into it• Levator & depressor of labii (lip) & anguli (angle of mouth)• Risorius & zygomaticus curl corner of mouth up in smile• Buccinator keeps food on top of teeth, blowing & sucking
Muscles around the Mouth
Orbicularis oris
Risorius
Depressor labii inferioris
BuccinatorZygomaticus major
Depressor anguli oris
Levator labii superioris
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Some of the Muscles used in Facial Expression
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Some of the Muscles used in Facial Expression
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Musculature of the Tongue• Intrinsic muscles = vertical, transverse & longitudinal• Extrinsic muscles connect tongue to hyoid, styloid
process, palate and inside of chin• Tongue shifts food onto teeth & pushes it into pharynx
Intrinsic tongue muscles
Extrinsic tongue muscles
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Muscles of Mastication• 4 Major muscles• Arise from skull & insert on
mandible• Temporalis & Masseter elevate
the mandible• Medial & Lateral Pterygoids
help elevate, but produce lateral Swinging of jaw used to grind with molars
Temporalis
Masseter
Lateral pterygoid
Medial pterygoid
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Suprahyoid Muscles and Swallowing• Digastric and Mylohyoid = open mouth• Geniohyoid = widens pharynx during swallowing• Stylohyoid = elevates hyoid• Thyrohyoid (an infrahyoid m.) = elevates larynx, closing glottis
Digastric Mylohyoid
StylohyoidThyrohyoid
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Triangles of the Neck
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Other Muscles involved in Swallowing
• Pharyngeal constrictors push food down throat• Infrahyoid muscles pulls the larynx downward • Intrinsic laryngeal muscles used to control speech
Pharyngeal constrictors
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Muscles of Respiration• Breathing requires the use of muscles
– diaphragm– external intercostal muscles– internal intercostal muscles
• Contraction of the first 2 produces Inspiration• Contraction of the last produces Forced Expiration• Normal Expiration requires little muscular activity
– elastic recoil of tissues and gravity collapsing the chest– only inspiratory muscles active in braking action, so
exhalation is smooth
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Muscles of Respiration -- Diaphragm
• Muscular dome between thoracic and abdominal cavities
• Muscle fascicles extend to a fibrous central tendon
• Contraction flattens it– increases the vertical dimension of the thorax drawing air into the
lungs– raises the abdominal pressure to help expel urine, feces and
facilitating childbirth
Central tendon
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Muscles of Respiration -- Intercostals
• External intercostals– extend downward and anteriorly
from rib to rib– pull ribcage up & outward during
inspiration• Internal intercostals
– extend upward and anteriorly from rib to rib
– pull ribcage downward during forced expiration
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Muscles of Respiration - Serratus
• Serratus posterior superior– elevates ribs 2-5 during
inspiration• Serratus posteriori inferior
– depresses ribs 9-12 during inspiration
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Muscles of the Abdomen• 4 Pairs of sheetlike muscles
– external oblique– internal oblique– transverse abdominis– rectus abdominis
• Functions– support the viscera– stabilize the vertebral column– help in respiration, urination, defecation & childbirth
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Rectus Abdominis & External Oblique• External oblique
– superficial– downward – anteriorly– inguinal
ligament
• Rectus abdominis– vertical, straplike– tendinous
intersections– rectus sheath– linea alba
External oblique Rectus abdominis
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Internal Oblique -Transverse Abdominis
• Internal oblique– anteriorly– upwards
• Transverse abdominis– horizontal fiber
orientation– deepest layer
Transverse abdominisInternal oblique
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Superficial Muscles of the Back
Trapezius
Latissimus dorsi
SemispinalisSplenius
Levator scapulaeRhomboideusSupraspinatusInfraspinatusTeres major
Gluteus maximusGluteus medius
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Muscles of the Back• Erector spinae group
– 3 columns muscle– extends from sacrum to ribs– extends vertebral column
• Semispinalis group– vertebrae to vertebrae– extends neck
• Multifidis– vertebrae to vertebrae– rotates vertebral column
• Quadratus lumborum– ilium to 12th rib– lateral flexion
Multifidis
Erector spinae
Quadratus lumborum
Semispinalis
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Muscles of the Pelvic Floor• 3 Layers of muscles span pelvic outlet
– support pelvic viscera• Region is called perineum
– diamond-shaped region bounded by pubic symphysis, coccyx and ischial tuberosities
– penetrated by anal canal, urethra & vagina– anteriorly = urogenital triangle; posteriorly= anal triangle
• 3 Layers or compartments of the perineum– superficial layer = Superficial perineal space– middle layer = Urogenital diaphragm & Anal sphincter– deep layer = Pelvic diaphragm
•
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Muscles in Superficial Perineal Space
• 3 Muscles found just deep to the skin• Ischiocavernosus = arises from ischial & pubic ramus• Bulbospongiosus = covers bulb of penis or encloses vagina• Superficial transverse perineus = extends from the ischial tuberosities to the central tendon of
the perineum• Function during sexual intercourse & voiding of urine
Bulbospongiosus
Ischiocavernosus
Superficial transverse perineus
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Muscles of the UG diaphragm
• Middle layer of pelvic floor contains Urogenital diaphragm and External anal sphincter
• Urogenital diaphragm = 2 muscles– deep transverse perineus m. supports pelvic viscera– external urethral sphincter m. inhibits urination
External anal sphincter
Urogenital diaphragm
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Muscles of the Pelvic Diaphragm
• Deepest compartment of the perineum • Pelvic diaphragm = 2 muscles
– levator ani m. supports viscera & functions during defecation– coccygeus m. supports and elevates pelvic floor
Levator ani
Coccygeus
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Hernias• Protrusion of viscera through muscular wall of
abdominopelvic cavity• Inguinal hernia
– most common type of hernia (rare in 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 navel
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Muscles Acting on the Pectoral Girdle• Originate on axial skeleton & insert onto
clavicle or scapula• Anterior muscle group = 2 muscles• Posterior muscle group = 4 muscles• Scapular movements produced include
– medial and lateral rotation of the scapula– elevation and depression of the scapula– protraction and retraction of the scapula
• Clavicle braces the shoulder & limits movement
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Anterior Scapular Muscle Group• Pectoralis Minor
– ribs 3-5 to coracoid process of scapula
– protracts & depresses scapula
– lifts ribs during forced expiration
• Serratus Anterior– ribs 1-9 to medial
border of scapula– abducts & rotates or
depresses scapula– throwing muscle
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Muscles Acting on the Scapula
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Posterior Scapular Muscle Group
• 4 Muscles – superficial = Trapezius– deep = Rhomboids & Levator scapulae
• Trapezius– rotate scapula upward– retract scapula– depress scapula
• With Levator scapulae & Rhomboids elevates scapula
• With Serratus anterior depresses scapula
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• Rhomboideus mm.– medial border of
scapula to C7-T1
Posterior Scapular Muscle Group• Levator scapulae
– from superior angle of scapula to C1-C4
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Muscles Acting on the Humerus• 9 Muscles cross the shoulder joint to the humerus
– 2 axial muscles arise from axial skeleton– prime movers of humerus in flexion & extension– arise from sternum & clavicle OR T7-L5 & ilium
Pectoralis major Latissimus dorsi
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• 7 scapular muscles arise from scapula– Deltoid is prime mover
• flexion, extension and abduction of humerus
– Coracobrachialis assists in flexion
– Teres major assists in extension– Remaining 4 form the rotator
cuff muscles that reinforce the shoulder joint capsule
Muscles Acting on the Humerus
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Posterior View of Chest in Cadaver
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Rotator Cuff Muscles
• Extending from posterior scapula to humerus – supraspinatus– infraspinatus – teres Minor
• Extending from anterior scapula to humerus – subscapularis
All 4 help reinforce joint capsule.
SupraspinatusInfraspinatus
Teres minor
Subscapularis
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Anterior View of Chest in Cadaver
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Muscles Acting on the Elbow• Principal flexors
– biceps brachii • inserts on radius
– brachialis • inserts on ulna
• Synergistic flexor– brachioradialis
• Prime extensor– triceps brachii
• inserts onto ulna
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CS Through Upper Limb & Forearm
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Supination & Pronation of the Forearm
Supination• Supinator muscle• Palm facing anteriorly
Pronation• Pronator teres and Pronator
quadratus mm.• Palm faces posteriorly
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Muscles of the Anterior Forearm• Flex/extend wrist and fingers, adduct/abduct wrist• Digitorum = inserts into fingers• Carpi = inserts onto carpal bones• Pollicis = inserts into thumb
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Muscles of the Posterior Forearm• Extension of wrist and fingers, Adduct/abduct wrist• Extension and abduction of thumb (pollicis)• Brevis = short, Ulnaris = on ulna side of forearm
Extensors
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• Thenar group = fleshy base of thumb muscles• Hypothenar group = base of little finger muscles• Midpalmar group = Interosseus mm. & Lumbrical mm.
Intrinsic Hand Muscles
Interosseus
Lumbrical
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Carpal Tunnel Syndromerepetitive motions causes
inflammation and pressure on median nerve
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Anterior Muscles Acting on the Hip• Iliopsoas muscle
– crosses anterior surface of hip joint & inserts on femur– iliacus portion arises from iliac fossa– psoas portion arises from lumbar vertebrae– major hip flexor
Iliopsoas
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Posterior Muscles Acting on the Hip
• Gluteus maximus– forms mass of the
buttock– prime hip extensor– provides most of lift
when you climb stairs• Iliotibial band
– band of fascia lata attached to the tibia
Gluteus maximus
Gluteus medius
Iliotibial band
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Deep Gluteal Muscles
• Most laterally rotate femur• Except: Gluteus minimus medially rotates femur• Important in walking to shift body weight when foot is
lifted• Quadratus femoris is adductor of hip• Piriformis & Gluteus minimus are abductors of hip
Quadratus femoris
Piriformis
Gluteus minimus
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Adductors of the Hip Joint
• 5 muscles act as adductors• Adductor magnus is also an
extensor of hip joint• Gracilis also is flexor of knee• Pectineus, Adductor brevis
and Adductor longus adduct the femur
Adductor longus
Adductor brevis
Pectineus
Adductor magnus
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Muscles Acting on the Knee• 4 headed muscle
attaches to tibial tuberosity– extends knee joint
• rectus femoris arises from ilium so flexes hip joint
• quadriceps femoris tendon attaches to patella
• patellar ligament attaches to tibia
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Anterior Thigh Muscles in Cadaver
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Muscles of the Leg
• Crural muscles are separated into 3 compartments.– anterior compartment (green)– fibular (lateral) compartment (blue)– posterior (superficial = brown) (deep = purple)
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Anterior Compartment of the Leg
• Extensor digitorum longus = extension of toes & ankle• Extensor hallucis longus = extension of big toe & ankle• Fibularis tertius = dorsiflexes and everts foot• Tibialis anterior = dorsiflexes and inverts foot
Extensor digitorum longus
Peroneus tertius
Extensor hallucis longus
Tibialis anterior
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Posterior Compartment of the LegSuperficial Group of Plantar Flexors
• Gastrocnemius = flexes knee and plantar flexes ankle• Soleus = plantar flexes ankle• Plantaris = flexes knee and plantar flexes ankle
GastrocnemiusSoleus
Plantaris
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Posterior Compartment of the LegDeep Group of Plantar Flexors
• Tibialis posterior, Flexor digitorum longus, and Flexor hallucis longus and are plantar flexors.
• Popliteus unlocks the knee joint for knee flexion.
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Lateral Compartment of the Leg
• 2 muscles in this compartment
• Both plantar flex and evert the foot
• Provides lift and forward thrust
Fibularis brevis
Fibularis longus
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Leg Muscles in the Cadaver
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Intrinsic Muscles of the Sole
• Four muscle layers • Support for the arches
– abduct & adduct the toes– flex the toes
• One dorsal muscle– extensor digitorum brevis
extends toes
Dorsal view
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Athletic Injuries• Vulnerable to sudden and intense stress• Proper conditioning and warm-up is needed• Common injuries
– shinsplints– pulled hamstrings– tennis elbow
• Treat initially with rest, ice, compression and elevation
• “No pain, no gain” is a dangerous misconception.