Muscle Tissue
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•
•
•
•
•
•
Types and characteristics of muscular tissue
Microscopic anatomy of skeletal muscle
Nerve-Muscle relationship
Behavior of skeletal muscle fibers
Behavior of whole muscles
Muscle metabolism
Cardiac and smooth muscle
11-1
Introduction to Muscle
• Movement is a fundamental characteristic
of all living things
• Cells capable of shortening and
converting the chemical energy of ATP
into mechanical energy
• Types of muscle
– skeletal, cardiac and smooth
• Physiology of skeletal muscle
– basis of warm-up, strength, endurance and
fatigue
11-2
Characteristics of Muscle
• Responsiveness (excitability)
– to chemical signals, stretch and electrical
changes across the plasma membrane
• Conductivity
– local electrical change triggers a wave of
excitation that travels along the muscle fiber
• Contractility -- shortens when stimulated
• Extensibility -- capable of being stretched
• Elasticity -- returns to its original resting
length after being stretched
11-3
Skeletal Muscle
• Voluntary striated muscle attached to
bones
• Muscle fibers (myofibers) as long as 30
cm
• Exhibits alternating light and dark
transverse bands or striations
– reflects overlapping arrangement of
internal contractile proteins
• Under conscious
control (voluntary)
11-4
Connective Tissue Elements
• Attachments between muscle and bone
– endomysium, perimysium, epimysium, fascia,
tendon
• Collagen is extensible and elastic
– stretches slightly under tension and recoils
when released
• protects muscle from injury
• returns muscle to its resting length
• Elastic components
– parallel components parallel muscle cells
– series components joined to ends of muscle11-5
The Muscle Fiber
11-6
Muscle Fibers
• Multiple flattened nuclei inside cell
membrane
– fusion of multiple myoblasts during
development
– unfused satellite cells nearby can multiply to
produce a small number of new myofibers
• Sarcolemma has tunnel-like infoldings or
transverse (T) tubules that penetrate the
cell
– carry electric current to cell interior
11-7
Muscle Fibers 2
• Sarcoplasm is filled with
– myofibrils (bundles of myofilaments)
– glycogen for stored energy and myoglobin
for binding oxygen
• Sarcoplasmic reticulum = smooth ER
– network around each myofibril
– dilated end-sacs (terminal cisternea) store
calcium
– triad = T tubule and 2 terminal cisternea
11-8
Thick Filaments
• Made of 200 to 500 myosin molecules
– 2 entwined polypeptides (golf clubs)
• Arranged in a bundle with heads directed
outward in a spiral array around the
bundled tails
– central area is a bare zone with no heads
11-9
Thin Filaments
• Two intertwined strands fibrous (F) actin
– globular (G) actin with an active site
• Groove holds tropomyosin molecules
– each blocking 6 or 7 active sites of G actins
• One small, calcium-binding troponin
molecule on each tropomyosin molecule
11-10
Elastic Filaments
• Springy proteins called titin
• Anchor each thick filament to Z disc
• Prevents overstretching of sarcomere
11-11
Regulatory and Contractile Proteins
• Myosin and actin are contractile proteins
• Tropomyosin and troponin = regulatory proteins
– switch that starts and stops shortening of muscle cell
– contraction activated by release of calcium into sarcoplasm
and its binding to troponin,
– troponin moves tropomyosin off the actin active sites
11-12
Overlap of Thick and Thin Filaments
11-13
Striations = Organization of Filaments
• Dark A bands (regions) alternating with lighter I bands (regions)
– anisotrophic (A) and isotropic (I) stand for the way these regions affect
polarized light
• A band is thick filament region
– lighter, central H band area
contains no thin filaments
• I band is thin filament region
– bisected by Z disc protein called
connectin, anchoring elastic and thin
filaments
– from one Z disc (Z line) to the next is a sarcomere
11-14
Striations and Sarcomeres
11-15
Relaxed and Contracted Sarcomeres
• Muscle cells shorten because their individual
sarcomeres shorten
– pulling Z discs closer together
– pulls on sarcolemma
• Notice neither thick nor thin filaments change
length during shortening
• Their overlap changes as sarcomeres shorten
11-16
Nerve-Muscle Relationships
• Skeletal muscle must be stimulated by
a nerve or it will not contract
• Cell bodies of somatic motor neurons
in brainstem or spinal cord
• Axons of somatic motor neurons =
somatic motor fibers
– terminal branches supply one muscle fiber
• Each motor neuron and all the muscle
fibers it innervates = motor unit
11-17
Motor Units
• A motor neuron and the muscle
fibers it innervates
– dispersed throughout the muscle
– when contract together causes weak
contraction over wide area
– provides ability to sustain long-term
contraction as motor units take turns
resting (postural control)
• Fine control
– small motor units contain as few as
20 muscle fibers per nerve fiber
– eye muscles
• Strength control
– gastrocnemius muscle has 1000
fibers per nerve fiber
11-18
Neuromuscular Junctions (Synapse)
• Functional connection between
nerve fiber and muscle cell
• Neurotransmitter (acetylcholine/ACh) released
from
nerve fiber stimulates muscle cell
• Components of synapse (NMJ)
– synaptic knob is swollen end of nerve fiber (contains
ACh)
– junctional folds region of sarcolemma
• increases surface area for ACh receptors
• contains acetylcholinesterase that breaks down ACh and
causes relaxation
– synaptic cleft = tiny gap between nerve and muscle
cells
– Basal lamina = thin layer of collagen and glycoprotein
11-19
over all of muscle fiber
The Neuromuscular Junction
11-20
Neuromuscular Toxins
• Pesticides (cholinesterase inhibitors)
– bind to acetylcholinesterase and prevent it
from degrading ACh
– spastic paralysis and possible suffocation
• Tetanus or lockjaw is spastic paralysis
caused by toxin of Clostridium bacteria
– blocks glycine release in the spinal cord and
causes overstimulation of the muscles
• Flaccid paralysis (limp muscles) due to
curare that competes with ACh
– respiratory arrest
11-21
Electrically Excitable Cells
• Plasma membrane is polarized or charged
– resting membrane potential due to Na+ outside
of cell and K+ and other anions inside of cell
– difference in charge across the membrane =
resting membrane potential (-90 mV cell)
• Stimulation opens ion gates in membrane
– ion gates open (Na+ rushes into cell and K+
rushes out of cell)
• quick up-and-down voltage shift = action potential
– spreads over cell surface as nerve signal
11-22
Muscle Contraction and
Relaxation
• Four actions involved in this process
– excitation = nerve action potentials lead to
action potentials in muscle fiber
– excitation-contraction coupling = action
potentials on the sarcolemma activate
myofilaments
– contraction = shortening of muscle fiber
– relaxation = return to resting length
• Images will be used to demonstrate the
steps of each of these actions
11-23
Excitation of a Muscle Fiber
11-24
Excitation (steps 1 and 2)
• Nerve signal opens voltage-gated calcium channels.
Calcium stimulates exocytosis of synaptic vesicles
containing ACh = ACh release into synaptic cleft.
11-25
Excitation (steps 3 and 4)
Binding of ACh to receptor proteins opens Na+ and K+
channels resulting in jump in RMP from -90mV to +75mV
11-26
forming an end-plate potential (EPP).
Excitation (step 5)
Voltage change in end-plate region (EPP) opens nearby
voltage-gated channels producing an action potential 11-27
Excitation-Contraction Coupling
11-28
Excitation-Contraction Coupling (steps 6 and 7)
Action potential spreading over sarcolemma enters T
tubules -- voltage-gated channels open in T tubules
causing calcium gates to open in SR
11-29
Excitation-Contraction Coupling (steps 8 and 9)
• Calcium released by SR binds to troponin
• Troponin-tropomyosin complex changes shape
11-30
and exposes active sites on actin
Contraction (steps 10 and 11)
• Myosin ATPase in myosin head hydrolyzes an
ATP molecule, activating the head and “cocking”
it in an extended position
11-31
• It binds to actin active site forming a cross-bridge
Contraction (steps 12 and 13)
• Power stroke =
myosin head releases
ADP and phosphate as
it flexes pulling the thin
filament past the thick
• With the binding of more
ATP, the myosin head
extends to attach to a
new active site
– half of the heads are bound to a thin
filament at one time preventing slippage
– thin and thick filaments do not become
shorter, just slide past each other (sliding
filament theory)
11-32
Relaxation (steps 14 and 15)
Nerve stimulation ceases and acetylcholinesterase
removes ACh from receptors. Stimulation of the
muscle cell ceases.
11-33
Relaxation (step 16)
• Active transport needed to pump calcium
back into SR to bind to calsequestrin
• ATP is needed for muscle relaxation as well
as muscle contraction
11-34
Relaxation (steps 17 and 18)
• Loss of calcium from sarcoplasm moves
troponin-tropomyosin complex over active sites
– stops the production or maintenance of tension
• Muscle fiber returns to its resting length due to
recoil of series-elastic components and
11-35
contraction of antagonistic muscles
Length-Tension Relationship
• Amount of tension generated depends on length
of muscle before it was stimulated
– length-tension relationship (see graph next slide)
• Overly contracted (weak contraction results)
– thick filaments too close to Z discs and can’t slide
• Too stretched (weak contraction results)
– little overlap of thin and thick does not allow for very
many cross bridges too form
• Optimum resting length produces greatest force
when muscle contracts
– central nervous system maintains optimal length
producing muscle tone or partial contraction
11-36
Length-Tension Curve
11-37
Muscle Twitch in Frog
• Threshold = voltage producing
an action potential
– a single brief stimulus at that
voltage produces a quick cycle of
contraction and relaxation called a
twitch (lasting less than 1/10
second)
• A single twitch contraction is
not strong enough to do any
useful work
11-38
Muscle Twitch in Frog 2
• Phases of a twitch contraction
– latent period (2 msec delay)
• only internal tension is generated
• no visible contraction occurs since
only elastic components are being
stretched
– contraction phase
• external tension develops as muscle
shortens
– relaxation phase
• loss of tension and return
to resting length as calcium returns to SR
11-39
Contraction Strength of Twitches
• Threshold stimuli produces twitches
• Twitches unchanged despite increased
voltage
• “Muscle fiber obeys an all-or-none law”
contracting to its maximum or not at all
– not a true statement since twitches vary in
strength
• depending upon, Ca2+ concentration, previous stretch
of the muscle, temperature, pH and hydration
• Closer stimuli produce stronger twitches
11-40
Recruitment and Stimulus Intensity
• Stimulating the whole nerve with higher and
higher voltage produces stronger contractions
• More motor units are being recruited
– called multiple motor unit summation
– lift a glass of milk versus a whole gallon of milk
11-41
Twitch and Treppe Contractions
• Muscle stimulation at variable frequencies
– low frequency (up to 10 stimuli/sec)
• each stimulus produces an identical twitch response
– moderate frequency (between 10-20 stimuli/sec)
• each twitch has time to recover but develops more
tension than the one before (treppe phenomenon)
– calcium was not completely put back into SR
– heat of tissue increases myosin ATPase efficiency
11-42
Incomplete and Complete Tetanus
• Higher frequency stimulation (20-40 stimuli/second)
generates gradually more strength of contraction
– each stimuli arrives before last one recovers
• temporal summation or wave summation
– incomplete tetanus = sustained fluttering contractions
• Maximum frequency stimulation (40-50 stimuli/second)
– muscle has no time to relax at all
– twitches fuse into smooth, prolonged contraction called
complete tetanus
– rarely occurs in the body
11-43
Isometric and Isotonic
Contractions
• Isometric muscle contraction
– develops tension without changing length
– important in postural muscle function and
antagonistic muscle joint stabilization
• Isotonic muscle contraction
– tension while shortening = concentric
– tension while lengthening = eccentric
11-44
Muscle Contraction Phases
• Isometric and isotonic phases of lifting
– tension builds though the box is not moving
– muscle begins to shorten
– tension maintained
11-45
ATP Sources
• All muscle contraction depends on ATP
• Pathways of ATP synthesis
– anaerobic fermentation (ATP production limited)
• without oxygen, produces toxic lactic acid
– aerobic respiration (more ATP produced)
• requires continuous oxygen supply, produces H2O and
11-46
CO2
Immediate Energy Needs
• Short, intense exercise (100
m dash)
– oxygen need is supplied by
myoglobin
• Phosphagen system
– myokinase transfers Pi groups
from one ADP to another
forming ATP
– creatine kinase transfers Pi
groups from creatine
phosphate to make ATP
• Result is power enough for 1
minute brisk walk or 6
seconds of sprinting
11-47
Short-Term Energy Needs
• Glycogen-lactic acid system takes over
– produces ATP for 30-40 seconds of
maximum activity
• playing basketball or running around baseball
diamonds
– muscles obtain glucose from blood and
stored glycogen
11-48
Long-Term Energy Needs
• Aerobic respiration needed for prolonged
exercise
– Produces 36 ATPs/glucose molecule
• After 40 seconds of exercise, respiratory and
cardiovascular systems must deliver enough
oxygen for aerobic respiration
– oxygen consumption rate increases for first 3-4
minutes and then levels off to a steady state
• Limits are set by depletion of glycogen and
blood glucose, loss of fluid and electrolytes
11-49
Fatigue
• Progressive weakness from use
– ATP synthesis declines as glycogen is
consumed
– sodium-potassium pumps fail to maintain
membrane potential and excitability
– lactic acid inhibits enzyme function
– accumulation of extracellular K+
hyperpolarizes the cell
– motor nerve fibers use up their acetylcholine
11-50
Oxygen Debt
• Heavy breathing after strenuous exercise
– known as excess postexercise oxygen
consumption (EPOC)
– typically about 11 liters extra is consumed
• Purposes for extra oxygen
– replace oxygen reserves (myoglobin, blood
hemoglobin, in air in the lungs and dissolved in
plasma)
– replenishing the phosphagen system
– reconverting lactic acid to glucose in kidneys and
liver
– serving the elevated metabolic rate that occurs as
long as the body temperature remains elevated by
exercise
11-51
Endurance
• Ability to maintain high-intensity
exercise for >5 minutes
– determined by maximum oxygen uptake
• VO2 max is proportional to body size, peaks at
age 20, is larger in trained athlete and males
– nutrient availability
• carbohydrate loading used by some athletes
– packs glycogen into muscle cells
– adds water at same time (2.7 g water with each
gram/glycogen)
» side effects include “heaviness” feeling
11-52
Strength and Conditioning
• Strength of contraction
– muscle size and fascicle arrangement
• 3 or 4 kg / cm2 of cross-sectional area
– size of motor units and motor unit recruitment
– length of muscle at start of contraction
• Resistance training (weight lifting)
– stimulates cell enlargement due to synthesis of
more myofilaments
• Endurance training (aerobic exercise)
– produces an increase in mitochondria, glycogen and
density of capillaries
11-53
The 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
11-54
Organization of Muscles
• 600 Human skeletal muscles
• General structural and functional topics
–
–
–
–
–
muscle shape and function
connective tissues of muscle
coordinated actions of muscle groups
intrinsic and extrinsic muscles
muscle innervation
• Regional descriptions
11-55
The Functions of Muscles
• Movement of body parts and organ
contents
• Maintain posture and prevent
movement
• Communication - speech, expression
and writing
• Control of openings and passageways
• Heat production
11-56
Connective Tissues of a Muscle
Tendon
Deep fascia
Epimysium
Perimysium
Endomysium
11-57
Connective Tissues of a Muscle
• Epimysium
– covers whole muscle belly
– blends into CT between muscles
• Perimysium
– slightly thicker layer of connective tissue
– surrounds bundle of cells called a fascicle
• Endomysium
– thin areolar tissue around each cell
– allows room for capillaries and nerve
fibers
11-58
Location of Fascia
• Deep fascia
– found between adjacent muscles
• Superficial fascia (hypodermis)
– adipose between skin and muscles
Superficial Fascia
Deep Fascia
11-59
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
11-60
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
11-61
Skeletal Muscle Shapes 1
11-62
Skeletal Muscle Shapes 2
• Fusiform muscles
– thick in middle and tapered at ends
– biceps brachii m.
• Parallel muscles have parallel fascicles
– rectus abdominis m.
• Convergent muscle
– broad at origin and tapering to a narrower insertion
• Pennate muscles
– fascicles insert obliquely on a tendon
– unipennate, bipennate or multipennate
– palmar interosseus, rectus femoris and deltoid
• Circular muscles
– ring around body opening
– orbicularis oculi
11-63
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
• Antagonist
– opposes the prime mover
– preventing excessive movement and injury
• Fixator
– prevents movement of bone
11-64
Muscle Actions during Elbow
Flexion
• Prime mover (agonist) =
brachialis
• Synergist = biceps brachii
• Antagonist = triceps brachii
• Fixator = muscle that holds
scapula firmly in
place
– rhomboideus m.
11-65
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.
11-66
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
11-67
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
muscles
– levator = elevates a body part
– profundus = deepest
– quadriceps = having 4 heads
11-68
Learning Strategy
• 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
– observe an articulated skeleton
– say the names aloud and check your
pronunciation
11-69
The Muscular System
11-70
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
11-71
Muscles in Facial Expression 1
11-72
Muscles in Facial Expression 2
11-73
Musculature of the Tongue
• Intrinsic muscles = vertical, transverse and
longitudinal
• Extrinsic muscles connect tongue to hyoid, styloid
process, palate and inside of chin
• Tongue shifts food onto teeth and pushes it into
pharynx
Intrinsic tongue muscles
Extrinsic tongue muscles
11-74
Muscles of Mastication
• 4 Major muscles
• Arise from skull and
insert on mandible
• Temporalis and
Masseter elevate the
mandible
• Medial and Lateral
Pterygoids help
elevate, but produce
lateral swinging of jaw
Temporalis
Masseter
Lateral pterygoid
Medial pterygoid
11-75
Suprahyoid Muscles and Swallowing
•
•
•
•
Digastric and Mylohyoid = open mouth
Geniohyoid = widens pharynx during swallowing
Stylohyoid = elevates hyoid
Thyrohyoid = elevates larynx, closing glottis
Digastric
Mylohyoid
Thyrohyoid
11-76
Triangles of the Neck
11-77
Muscles involved in Swallowing
Pharyngeal constrictors
• Pharyngeal constrictors push food down throat
• Infrahyoid muscles pulls larynx downward
• Intrinsic laryngeal muscles control speech
11-78
Muscles of Respiration
• Breathing requires the use of muscles
– Diaphragm and external intercostal muscles
– internal intercostal muscles
• Contraction of first 2 produces inspiration
• Contraction of last produces forced expiration
• Normal expiration requires little muscular
activity
– elastic recoil and gravity collapses the chest
– inspiratory muscles active in braking action, so
exhalation is smooth
11-79
Muscles of Respiration -- Diaphragm
Central tendon
• 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
11-80
Muscles of Respiration - Intercostals
• External intercostals
– extend downward and
anteriorly from rib to rib
– pull ribcage up and outward
during inspiration
• Internal intercostals
– extend upward and anteriorly
from rib to rib
– pull ribcage downward
during forced expiration
11-81
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 and childbirth
11-82
Rectus Abdominis and External Oblique
• External oblique
–
–
–
–
superficial
downward
anteriorly
inguinal
ligament
External oblique
• Rectus
abdominis
– vertical, straplike
– tendinous
intersections
– rectus sheath
– linea alba
Rectus abdominis
11-83
Internal Oblique -Transverse Abdominis
• Internal oblique
– anteriorly
– upwards
Internal oblique
• Transverse abdominal
– horizontal fiber
orientation
– deepest layer
Transverse
abdominis
11-84
Superficial Muscles of Back
Trapezius
Latissimus dorsi
Semispinalis
Splenius
Levator scapulae
Rhomboideus
Supraspinatus
Infraspinatus
Teres major
Gluteus maximus
Gluteus medius
11-85
Muscles of the Back
• Erector spinae
group
– 3 columns muscle
– 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
Semispinalis
Erector spinae
Multifidis
Quadratus
lumborum
11-86
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 and vagina
– anteriorly = urogenital triangle; posteriorly= anal
triangle
• 3 Layers or compartments of the perineum
– superficial layer = Superficial perineal space
– middle layer = Urogenital diaphragm and Anal
sphincter
– deep layer = Pelvic diaphragm
11-87
Superficial Perineal Space
•
•
•
•
3 Muscles found just deep to the skin
Ischiocavernosus = arises ischial and pubic ramus
Bulbospongiosus = covers bulb of penis or encloses vagina
Function during intercourse and voiding of urine
11-88
Muscles of 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
11-89
Muscles of Pelvic Diaphragm
Levator ani
Coccygeus
• Deepest compartment of the perineum
• Pelvic diaphragm = 2 muscles
– levator ani m. supports viscera and defecation
– coccygeus m. supports and elevates pelvic floor
11-90
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
11-91
Muscles on Pectoral Girdle
• Originate on axial skeleton and 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 and limits
movement
11-92
Anterior Scapular Muscles
• Pectoralis Minor
– ribs 3-5 to coracoid
process of scapula
– protracts and
depresses scapula
– lifts ribs during forced
expiration
• Serratus Anterior
– ribs 1-9 to medial
border of scapula
– abducts and rotates
or depresses scapula
– throwing muscle
11-93
Muscles Acting on Scapula
11-94
Posterior Scapular Muscles
• 4 Muscles
– superficial = Trapezius
– deep = Rhomboids and
Levator scapulae
• Trapezius
– rotate scapula upward
– retract scapula
– depress scapula
• With Levator scapulae and
Rhomboids elevates
scapula
• With Serratus anterior
depresses scapula
11-95
Posterior Scapular Muscles
• Rhomboideus mm.
– medial border of
scapula to C7-T1
• Levator scapulae
– from superior angle of
scapula to C1-C4
11-96
Muscles Acting on Humerus
• Crossing shoulder joint to humerus
– 2 arise from axial skeleton
• prime movers in flexion and extension
– arise from sternum and clavicle or T7-L5 and ilium
Pectoralis major
Latissimus dorsi
11-97
Muscles Acting on Humerus
• 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
11-98
Posterior View of Cadaver Chest
11-99
Rotator Cuff Muscles
• Extending from posterior
scapula to humerus
– supraspinatus
– infraspinatus
– teres minor
Supraspinatus
Subscapularis
Infraspinatus
• Extending from anterior
scapula to humerus
– subscapularis
All 4 help reinforce joint capsule.
11-100
Rotator Cuff Muscles
11-101
Anterior View of Cadaver Chest
11-102
Muscles Acting on Elbow
• Principal flexors
– biceps brachii
• inserts on radius
– brachialis
• inserts on ulna
• Synergistic flexor
– brachioradialis
• Prime extensor
– triceps brachii
• inserts onto ulna
11-103
CS Upper Limb and Forearm
11-104
Supination and Pronation
Supination
• Supinator muscle
• Palm facing anteriorly
Pronation
• Pronator teres and Pronator
quadratus mm.
• Palm faces posteriorly
11-105
Muscles of Anterior Forearm
•
•
•
•
Flex/extend wrist and fingers, adduct/abduct wrist
Digitorum = inserts into fingers
Carpi = inserts onto carpal bones
Pollicis = inserts into thumb
11-106
Muscles of 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
11-107
Intrinsic Hand Muscles
• Thenar group = fleshy base of thumb muscles
• Hypothenar group = base of little finger muscles
• Midpalmar group = Interosseus mm. and Lumbrical
mm.
11-108
Carpal Tunnel Syndrome
Repetitive motions cause
inflammation and
pressure on median nerve
11-109
Anterior Muscles Acting on the Hip
• Iliopsoas muscle
– crosses anterior
surface of hip joint
and inserts on femur
– iliacus portion
arises from iliac
fossa
– psoas portion arises
Iliopsoas
from lumbar
vertebrae
– major hip flexor
11-110
Posterior Muscles Acting on Hip
• Gluteus maximus
– forms mass of the
buttock
– prime hip extensor
– provides most of
lift when you climb
stairs
Gluteus medius
Gluteus maximus
Iliotibial
band
• Iliotibial band
– band of fascia lata
attached to the
tibia
11-111
Deep Gluteal
Muscles
Gluteus minimus
Piriformis
Quadratus
femoris
• Most laterally rotate femur
• Except: Gluteus minimus medially
rotates femur
• Shifts body weight when foot is lifted
• Quadratus femoris is adductor of hip
• Piriformis and Gluteus minimus = hip
abductors
11-112
Adductors of the Hip Joint
• 5 muscles act as
adductors
• Adductor magnus
is hip joint
extensor
• Gracilis is flexor of
knee
• Pectineus,
Adductor brevis
and Adductor
longus adduct
femur
Pectineus
Adductor
brevis
Adductor
longus
Adductor magnus
11-113
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 11-114
Anterior Thigh Cadaver Muscles
11-115
Muscles of the Leg
• Crural muscles are separated into 3 compartments.
– anterior compartment (green)
– fibular (lateral) compartment (blue)
– posterior (superficial = brown) (deep = purple)
11-116
Anterior Compartment of Leg
•
•
•
•
Extensor digitorum longus = extension of toes and ankle
Extensor hallucis longus = extension of big toe and ankle
Fibularis tertius = dorsiflexes and everts foot
Tibialis anterior = dorsiflexes and inverts foot
11-117
Posterior Compartment of Leg
Superficial Group of Plantar Flexors
Gastrocnemius
Plantaris
Soleus
• Gastrocnemius = flexes knee and plantar flexes ankle
• Soleus = plantar flexes ankle
11-118
Posterior Compartment of Leg
Deep 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.
11-119
Lateral Compartment of the Leg
Fibularis longus
Fibularis brevis
• 2 muscles in this
compartment
• Both plantar flex
and evert the foot
• Provides lift and
forward thrust
11-120
Intrinsic Muscles of Sole
• Four muscle
layers
• Support for
arches
– abduct and
adduct the toes
– flex the toes
• One dorsal
muscle
– extensor
digitorum
brevis extends
toes
Dorsal
view
11-121