Download Muscles and Muscle Tissue

Muscles and Muscle Tissue
Muscle Overview
• The three types of muscle tissue are
skeletal, cardiac, and smooth
• These types differ in structure, location,
function, and means of activation
Cardiac
Skeletal
Smooth
Muscle Comparison
Cardiac
Skeletal
Smooth
Nuclei
Single, on side
Many, on side
Single, centered
Striations
Striated
Striated
No striations
Shape
Branched
Cylinders
Spindles
Intercalated
discs
Present
None
None
Skeletal Muscle
Tissue
• Packaged in skeletal muscles that attach to
and cover the bony skeleton
• Has obvious stripes called striations
• Is controlled voluntarily (i.e., by conscious
control)
• Contracts rapidly but tires easily
• Is responsible for overall body motility
Cardiac Muscle
Tissue
• Occurs only in the heart
• Is striated like skeletal muscle but is not
voluntary
• Contracts at a fairly steady rate set by the
heart’s pacemaker
• Neural controls allow the heart to respond
to changes in bodily needs
– Heart muscle has variable contractility
Smooth Muscle
Tissue
• Found in the walls of hollow visceral
organs, such as the stomach, urinary
bladder, and respiratory passages
• Forces food and other substances through
internal body channels
• It is not striated and is involuntary
Muscle Similarities
• Skeletal and smooth muscle cells are
elongated and are called muscle fibers
• Muscle terminology is similar
– Sarcolemma – muscle plasma membrane
– Sarcoplasm – cytoplasm of a muscle cell
– Prefixes – myo, mys, and sarco all refer to
muscle
Functional Characteristics of
Muscle Tissue
• Excitability, or irritability – the ability to
receive and respond to stimuli
• Contractility – the ability to shorten forcibly
• Extensibility – the ability to be stretched or
extended
• Elasticity – the ability to recoil and resume
the original resting length
Skeletal Muscle
Skeletal Muscle
• Each muscle is a discrete organ
composed of muscle tissue, blood vessels,
nerve fibers, and connective tissue
Skeletal Muscle: Attachments
• Most skeletal muscles span joints and are
attached to bone in at least two places
• When muscles contract the movable bone,
the muscle’s insertion moves toward the
immovable bone, the muscle’s origin
Insertion
Origin
Microscopic Anatomy of a
Skeletal Muscle Fiber
• Each fiber is a long,
cylindrical cell with
multiple nuclei just
beneath the sarcolemma
• Fibers are 10 to 100 m
in diameter, and up to
hundreds of centimeters
long
• Each cell is a syncytium
produced by fusion of
embryonic cells
Microscopic Anatomy of a Skeletal
Muscle Fiber
Microscopic
Anatomy of
a Skeletal
Muscle Fiber
Microscopic Anatomy of a Skeletal
Muscle Fiber
• Fibers contain the usual organelles, myofibrils,
sarcoplasmic reticulum, and T tubules
Microscopic Anatomy of a Skeletal
Muscle Fiber
• Myofibrils are densely packed,
rodlike contractile elements
• They make up most of the
muscle volume
Myofibrils
• The
arrangement
of myofibrils
within a fiber
is such that a
perfectly
aligned
repeating
series of
• Dark A bands
• Light I bands
Sarcomeres
• The smallest contractile unit of a muscle
• The region of a myofibril between two
successive Z discs
– Z-disc – coin-shaped sheet of proteins
(connectins) that anchors the thin filaments
and connects myofibrils to one another
Sarcomeres
• Composed of myofilaments made up of
contractile proteins
– Myofilaments are of two types – thick and thin
• Thick
• Thin
Myofilaments: Banding Pattern
• Thick filaments – extend the entire length
of an A band (Myosin)
• Thin filaments – extend across the I band
and partway into the A band (Actin)
Myofilaments: Banding Pattern
• Thin filaments do not overlap thick
filaments in the lighter H zone
Myofilaments: Banding Pattern
Please
Know
Ultrastructure of Myofilaments:
Thick Filaments
• Thick filaments are composed of the
protein myosin
• Each myosin molecule has a rodlike tail
and two globular heads
– Tails – two interwoven, heavy polypeptide
chains
– Heads – two smaller, light polypeptide chains
called cross bridges
Ultrastructure of Myofilaments:
Thick Filaments
• Thick filaments are composed of several
myosin molecules bound together.
Ultrastructure of Myofilaments:
Thin Filaments
Ultrastructure of Myofilaments:
Thin Filaments
• Thin filaments are chiefly composed of the
protein actin
• The subunits contain the active sites to which
myosin heads attach during contraction
• Tropomyosin and troponin are regulatory
subunits bound to actin
Ultrastructure of Myofilaments:
Thin Filaments
Muscle Contraction
• Actin/myosin will automatically slide
against eachother if the troponin is moved
aside.
Muscle Contraction
• So the process of muscle contraction is get the
tropomyosin to move aside, the filaments will
independently burn ATP and slide along
eachother.
• The question then is how do you get the
tropomyosin to move aside. The answer is Ca2+.
Muscle Contraction
• Muscle contraction takes place in two
(complicated) steps.
– The first part is getting the Ca2+
released. This step is called excitationcontraction coupling.
• The second part is Ca2+ causing the
muscle fibers to move. This step is called
the sliding filament model.
Muscle Contraction
ExcitationContraction
coupling
Sliding
filament
model
Muscle Contraction
• First, excitation contraction coupling.
– The process of getting Ca2+ released onto the
muscle fiber.
Ca2+ is stored in the Sarcoplasmic
Reticulum (SR)
• SR is an elaborate, smooth endoplasmic
reticulum that mostly runs longitudinally and
surrounds each myofibril
• Paired terminal cisternae form perpendicular
cross channels
• Elongated tubes called T tubules penetrate into
the cell’s interior at each A band–I band junction
• T tubules associate with
the paired terminal
cisternae to form triads
Sarcoplasmic Reticulum (SR)
T tubules are continuous
with the sarcolemma and
then spread out to have a
nice conduction system to
the myofibrils. Thus, you
can distribute Ca2+
quickly.
We will also see in a little bit
that there is also a tight
electrical connection. So,
when the sarcolemma is
activated, the T-tubules are
activated as well.
Skeletal Muscle Contraction
•
Basic steps in skeletal muscle
contraction
1. Stimulation by a nerve ending
– Steps in neurotransmission lead to ACh
release
2. ACh opens Na/K channels, starts an AP
3. The AP travels along the sarcolemma and
then down the T-tubules.
4. AP in T-tubules stimulate voltage-dependent
Ca2+ channels in the SR to release Ca2+ .
5. Have a rise in intracellular Ca2+ levels, the
final trigger for contraction
Neuromuscular Junction
•
The neuromuscular junction is the point where
neuron meets muscle and is formed by two parts:
1. Axonal endings, synaptic vesicles that contain the
neurotransmitter acetylcholine (ACh)
2. The motor end plate of a muscle, which is a
specific part of the sarcolemma that contains ACh
receptors and helps form the neuromuscular
junction
Neuromuscular Junction
Neuromuscular Junction
•
When a nerve impulse reaches the end of an
axon at the neuromuscular junction, you get
basic neurotransmitter release.
1. Axon terminal +30mV
2. Ca2+ channels open, causes acetylcholine release.
3. ACh moves across the synaptic cleft and stimulates
nAChR receptors (directly) to open Na+ (and K+)
channels.
4. Depolarize the sarcolemma and initiate an action
potential.
Destruction of Acetylcholine
• Remember the three ways
neurotransmitter is removed from the
cleft? (reuptake, enzyme, diffuse away).
• At nAChRs, ACh is quickly destroyed by
the enzyme acetylcholinesterase
• This destruction prevents continued
muscle fiber contraction in the absence of
additional stimuli
Interactive Physiology
Action Potential: Electrical
Conditions of a Polarized
Sarcolemma
• The outside
(extracellular) face
is positive, while
the inside face is
negative
• This difference in
charge is the
resting membrane
potential
Action Potential: Electrical
Conditions of a Polarized
Sarcolemma
• The predominant
extracellular ion is
Na+
• The predominant
intracellular ion is
K+
• The sarcolemma
is relatively
impermeable to
both ions
Action Potential: Depolarization
and Generation of the Action
Potential
• An axonal
terminal of a
motor neuron
releases ACh and
causes a patch of
the sarcolemma
to become
permeable to Na+
(sodium channels
open)
•
Action Potential: Depolarization
and Generation of the Action
Na+ enters the Potential
cell, and the
resting potential
is decreased
(depolarization
occurs)
• If the stimulus is
strong enough,
an action
potential is
initiated
Action Potential: Propagation of
the Action Potential
• Polarity reversal of
the initial patch of
sarcolemma changes
the permeability of
the adjacent patch
• Voltage-regulated Na+
channels now open in
the adjacent patch
causing it to
depolarize
Action Potential: Propagation of
the Action Potential
• Thus, the action
potential travels
rapidly along the
sarcolemma
• Once initiated, the
action potential is
unstoppable, and
ultimately results
in the contraction
of a muscle
Action Potential: Repolarization
• Immediately after
the depolarization
wave passes, the
sarcolemma
permeability
changes
• Na+ channels close
and K+ channels
open
• K+ diffuses from the
cell, restoring the
electrical polarity of
the sarcolemma
Action Potential: Repolarization
• Repolarization
occurs in the same
direction as
depolarization, and
must occur before
the muscle can be
stimulated again
(refractory period)
• The ionic
concentration of the
resting state is
restored by the
Na+-K+ pump
Excitation-Contraction Coupling
• Once generated, the action potential:
– Is propagated along the sarcolemma
– Travels down the T tubules
– Triggers Ca2+ release from terminal cisternae
of the SR
• Muscle movie 2
Sliding Filament Model
• We now transition to the Sliding Filament
Model
• Ca2+ binds to troponin and causes:
– The blocking action of tropomyosin to cease
– Actin active binding sites are exposed and
myosin binds.
Role of Ionic Calcium (Ca2+) in the
Contraction Mechanism
•
At low intracellular
Ca2+ concentration:
1. Tropomyosin blocks
the binding sites on
actin
2. Myosin cross bridges
cannot attach to
binding sites on actin
3. The relaxed state of
the muscle is
enforced
Role of Ionic Calcium (Ca2+) in the
Contraction Mechanism
•
At higher
intracellular Ca2+
concentrations:
1. Additional calcium binds
to troponin (inactive
troponin binds two Ca2+)
2. Calcium-activated
troponin undergoes a
conformational change
3. This change moves
tropomyosin away from
actin’s binding sites
2+
(Ca )
Role of Ionic Calcium
in the
Contraction Mechanism
• Myosin head
can now bind
and cycle
• This permits
contraction
(sliding of the
thin filaments by
the myosin
cross bridges)
to begin
Sliding Filament Model of
Contraction
• Each myosin head binds and detaches
several times during contraction, acting
like a ratchet to generate tension and
propel the thin filaments to the center of
the sarcomere
• As this event
occurs throughout
the sarcomeres, the
muscle shortens
Sequential Events of
Contraction
1. Cross bridge formation – myosin cross bridge
attaches to actin filament
2. Working (power) stroke – myosin head pivots
and pulls actin filament toward M line
3. Cross bridge detachment – ATP attaches to
myosin head and the cross bridge detaches
4. “Cocking” of the myosin head – energy from
hydrolysis of ATP cocks the myosin head into
the high-energy state
Sequential Events of Contraction
Sliding Filament Model
• Thin filaments slide past the thick ones so that
the actin and myosin filaments overlap to a
greater degree
• In the relaxed state, thin and thick filaments
overlap only slightly
• Upon stimulation, myosin heads bind to actin
and sliding begins
Movie
• Muscle movie 3
• http://www.sci.sdsu.edu/movies/actin_myo
sin_gif.html
Random Points in Muscle
Physiology
• Isotonic vs. isometric
• Motor unit (large vs. small)
• Contraction strength
– Summation
– Recruitment
• Strength, speed and endurance
– Energy of contraction
Contraction of Skeletal Muscle
(Organ Level)
• Contraction of muscle fibers (cells) and
muscles (organs) is similar
• The two types of muscle contractions are:
– Isometric contraction – increasing muscle
tension (muscle does not shorten during
contraction) (holding)
– Isotonic contraction – decreasing muscle
length (muscle shortens during contraction)
(lifting)
Contraction of Skeletal Muscle
(Organ Level)
– Isotonic contraction
decreasing muscle
length (muscle
shortens during
contraction) (lifting)
– Isometric contraction
increasing muscle
tension (muscle does
not shorten during
contraction) (holding)
Motor Unit: The NerveMuscle Functional Unit
• A motor unit is a motor neuron and all the muscle
fibers it supplies (four to several hundred)
• Muscles that control fine movements (fingers,
eyes) have small motor units
• Large weight-bearing muscles (thighs, hips) have
large motor units
• Muscle fibers from a motor unit are spread
throughout the muscle; therefore, contraction of
a single motor unit causes weak contraction of
the entire muscle
Motor Unit: The Nerve-Muscle
Functional Unit
If the neuron
extended to just 4
muscle fibers, you
would have a small
motor unit. If the
neuron extended to
several hundred
muscle fibers, you
would have a large
motor unit.
Motor Unit 1 is (slightly) smaller than Motor unit 2
Contraction
Strength
• There are two ways you
can alter contraction
strength.
– Changing the frequency
of stimulation
• Wave summation/Tetany
– Changing the strength of
the stimulus
• Recruitment
Muscle Response to Varying
Stimuli
• A single stimulus results in a single contractile
response – a muscle twitch
• Frequently delivered stimuli (muscle does not
have time to completely relax) increases
contractile force – wave summation
Treppe: The Staircase Effect
• Staircase – increased contraction in
response to multiple stimuli of the same
strength
• Contractions increase because:
– There is increasing availability of Ca2+ in the
sarcoplasm
– Muscle enzyme
systems become
more efficient because
heat is increased
Recruitment
• Recruitment, brings
more and more
muscle fibers into
play
Measures of Muscle Function
• Muscle function can be measured in either
strength, speed, and endurance.
Muscle Performance: Strength
• Strength
varies by:
– Number of
fibers
– Size of
fibers
– Tetany
– Length at
contraction
Muscle Performance: Speed and
Durability
• Speed and
endurance are
dependent on
how the muscle
uses energy
(ATP or other
sources)
• So, how does
muscle
generate ATP?
Muscle Metabolism: Energy for
Contraction
• ATP is the only source used directly for
contractile activity
• As soon as available stores of ATP are
gone (4-6 seconds), ATP is regenerated
by one of three ways:
1. The interaction of ADP with creatine
phosphate (CP)
2. Anaerobic glycolysis
3. Aerobic respiration
Muscle Metabolism: Energy for
Contraction
Muscle Metabolism: Anaerobic
Glycolysis
• When muscle contractile activity reaches
70% of maximum:
– Bulging muscles compress blood vessels
– Oxygen delivery is impaired
– Pyruvic acid is converted into lactic acid
Muscle Fatigue
• Muscle fatigue – the muscle is in a state of
physiological inability to contract
• Muscle fatigue occurs when:
– ATP production fails to keep pace with ATP
use
– There is a relative deficit of ATP, causing
contractures
– Lactic acid accumulates in the muscle
– Ionic imbalances are present
Muscle Fiber Type: Functional
Characteristics
• Speed of contraction – determined by
speed in which ATPases split ATP
– The two types of fibers are slow and fast
• ATP-forming pathways
– Oxidative fibers – use aerobic pathways
– Glycolytic fibers – use anaerobic glycolysis
• These two criteria define three categories
– slow oxidative fibers, fast oxidative
fibers, and fast glycolytic fibers
Muscle Fiber Type: Speed of
Contraction
• Slow oxidative fibers contract
slowly, have slow acting myosin
ATPases, and are fatigue resistant
• Fast oxidative fibers contract
quickly, have fast myosin
ATPases, and have moderate
resistance to fatigue
• Fast glycolytic fibers contract
quickly, have fast myosin
ATPases, and are easily fatigued
Muscle Fiber Type: Speed of
Contraction
Type I
(slow
oxidative)
Type IIa
(fast oxidative)
Type IIx (IIb)
(fast glycolytic
Smooth Muscle
• Composed of spindle-shaped fibers
with a diameter of 2-10 m and lengths of
several hundred m
• Organized into two layers (longitudinal and
circular) of closely apposed fibers
• Found in walls of hollow organs (except the
heart)
• Have essentially the same contractile
mechanisms as skeletal muscle
Smooth Muscle
Innervation of Smooth Muscle
• Smooth muscle lacks neuromuscular
junctions
• Innervating nerves have bulbous swellings
called varicosities
• Varicosities release neurotransmitters into
wide synaptic
clefts called
diffuse junctions
Microscopic Anatomy of Smooth
Muscle
• SR is less developed than in skeletal
muscle and lacks a specific pattern
• T tubules are absent
• Ca2+ is sequestered in the extracellular
space near infoldings called caveoli,
allowing rapid influx when channels are
opened
• There are no visible striations and no
sarcomeres
• Thin and thick filaments are present
Proportion and Organization of
Myofilaments in Smooth Muscle
Contraction of Smooth Muscle
• Whole sheets of smooth muscle
exhibit slow, synchronized
contraction
• They contract in unison, reflecting
their electrical coupling with gap
junctions
• Action potentials are transmitted from
cell to cell
• Some smooth muscle cells:
– Act as pacemakers and set the
contractile pace for whole sheets
of muscle
– Are self-excitatory and depolarize
without external stimuli
Contraction Mechanism
• Actin and myosin interact according to the
sliding filament mechanism
• The final trigger for contractions is a rise in
intracellular Ca2+
• Ca2+ is released from the SR and from the
extracellular space
• Ca2+ interacts with calmodulin and myosin light
chain kinase to activate myosin
• Basically, whereas in skeletal muscle, Ca moves
tropomyosin, in smooth muscle the sliding
filament mechanism is not automatic. Ca
intervenes to allow each step to move forward.
Role of Calcium Ion
1. Ca2+ binds to calmodulin and activates it
2. Activated calmodulin activates the kinase
enzyme
3. Activated kinase transfers phosphate
from ATP to myosin cross bridges
4. Phosphorylated cross bridges interact
with actin to produce shortening
5. Smooth muscle relaxes when
intracellular Ca2+ levels drop
Role of Calcium Ion
Special Features of Smooth
Muscle Contraction
• Unique characteristics of smooth muscle
include:
– Smooth muscle tone
– Slow, prolonged contractile activity
– Low energy requirements
– Response to stretch
Response to Stretch
• Smooth muscle exhibits a
phenomenon called stressrelaxation response in which:
– Smooth muscle responds to stretch only
briefly, and then adapts to its new length
– The new length, however,
retains its ability to contract
– This enables organs such
as the stomach and bladder
to temporarily store contents
Muscular Dystrophy
• Muscular dystrophy – group of inherited muscledestroying diseases where muscles enlarge due
to fat and connective tissue deposits, but muscle
fibers atrophy
• Duchenne muscular dystrophy (DMD)
– Inherited, sex-linked disease carried by females and
expressed in males (1/3500)
– Diagnosed between the ages of 2-10
– Victims become clumsy and fall frequently as their
muscles fail
Muscular Dystrophy
– Progresses from the extremities upward, and
victims die of respiratory failure in their 20s
– Caused by a lack of the cytoplasmic protein
dystrophin
– There is no cure,
but myoblast transfer
therapy shows promise
The Muscular System
Interactions of Skeletal Muscles
• Skeletal muscles work together or in
opposition
• Muscles only pull (never push)
• As muscles shorten, the insertion
generally moves toward the origin
• Whatever a muscle (or group of muscles)
does, another muscle (or group) “undoes”
Muscle Classification:
Functional Groups
• Prime movers – provide the major force for
producing a specific movement
• Antagonists – oppose or reverse a
particular movement
• Synergists
– Add force to a movement
– Reduce undesirable or unnecessary
movement
• Fixators – synergists that immobilize a
bone or muscle’s origin
Naming Skeletal Muscles
• Location of muscle – bone or body region
associated with the muscle
• Shape of muscle – e.g., the deltoid muscle
(deltoid = triangle)
• Relative size – e.g., maximus (largest),
minimus (smallest), longus (long)
• Direction of fibers – e.g., rectus (fibers run
straight), transversus, and oblique (fibers
run at angles to an imaginary defined axis)
Naming Skeletal Muscles
• Number of origins – e.g., biceps (two
origins) and triceps (three origins)
• Location of attachments – named
according to point of origin or insertion
• Action – e.g., flexor or extensor, as in the
names of muscles that flex or extend,
respectively
Arrangement of Fascicles
• Parallel – fascicles run parallel to the long
axis of the muscle (e.g., sartorius)
• Fusiform – spindle-shaped muscles (e.g.,
biceps brachii)
• Pennate – short fascicles that attach
obliquely to a central tendon running the
length of the muscle (e.g., rectus femoris)
• Convergent – fascicles converge from a
broad origin to a single tendon insertion
(e.g., pectoralis major)
• Circular – fascicles are arranged in
concentric rings (e.g., orbicularis oris)
Arrangement of Fascicles
Parallel – fascicles run
parallel to the long axis of the
muscle (e.g., sartorius)
Fusiform – spindle-shaped
muscles (e.g., biceps brachii)
Pennate – short fascicles that
attach obliquely to a central
tendon running the length of
the muscle (e.g., rectus
femoris)
Convergent – fascicles
converge from a broad origin
to a single tendon insertion
(e.g., pectoralis major)
Circular – fascicles are
arranged in concentric rings
(e.g., orbicularis oris)
Major Skeletal
Muscles:
Anterior View
• The 40
superficial
muscles here
are divided
into 10
regional areas
of the body
Figure 10.4b
Major Skeletal
Muscles:
Posterior View
• The 27
superficial
muscles here
are divided
into seven
regional areas
of the body
Figure 10.5b
Muscles: Name, Action, and
Innervation
• Name and description of the muscle – be
alert to information given in the name
• Origin and insertion – there is always a
joint between the origin and insertion
• Action – best learned by acting out a
muscle’s movement on one’s own body
• Nerve supply – name of major nerve that
innervates the muscle
Expectations for the remainder of
these slides.
• We’ll do muscles in AP2.
• You could always start studying now.
Muscles of the Scalp
• Epicranius (occipitofrontalis) – bipartite
muscle consisting of the:
– Frontalis
– Occipitalis
• These two muscles have alternate actions
of pulling the scalp forward and backward
Muscles of the Face
• 11 muscles are involved in lifting the
eyebrows, flaring the nostrils, opening and
closing the eyes and mouth, and smiling
• All are innervated by cranial nerve VII
(facial nerve)
• Usually insert in skin (rather than bone),
and adjacent muscles often fuse
Muscles of the Face
Muscles of Mastication
• There are four pairs of muscles involved in
mastication
– Prime movers – temporalis and masseter
– Grinding movements – pterygoids and
buccinators
• All are innervated by cranial nerve V
(trigeminal nerve)
Muscles of Mastication
Muscles of Mastication
Extrinsic Tongue Muscles
• Three major muscles that anchor and
move the tongue
• All are innervated by cranial nerve XII
(hypoglossal nerve)
Extrinsic Tongue Muscles
Muscles of the Anterior Neck and
Throat: Suprahyoid
• Four deep throat muscles
– Form the floor of the oral cavity
– Anchor the tongue
– Elevate the hyoid
– Move the larynx superiorly during swallowing
Muscles of the Anterior Neck
and Throat: Suprahyoid
Muscles of the Anterior Neck
and Throat: Infrahyoid
• Straplike muscles that depress the hyoid
and larynx during swallowing and
speaking
Muscles of the Anterior Neck
and Throat: Infrahyoid
Muscles of the Neck: Head
Movements
• Major head flexor is the
sternocleidomastoid
• Synergists to head flexion are the
suprahyoid and infrahyoid
• Lateral head movements are
accomplished by the sternocleidomastoid
and scalene muscles
• Head extension is accomplished by the
deep splenius muscles and aided by the
superficial trapezius
Muscles of the Neck: Head
Movements
Muscles of the Neck: Head
Movements
Trunk Movements: Deep Back
Muscles
• The prime mover of back extension is the
erector spinae
• Erector spinae, or sacrospinalis, muscles
consist of three columns on each side of the
vertebrae – iliocostalis, longissimus, and
spinalis
• Lateral bending of the back is accomplished by
unilateral contraction of these muscles
• Other deep back extensors include the
semispinalis muscles and the quadratus
lumborum
Trunk Movements: Deep Back
Muscles
Trunk Movements: Short Muscles
• Four short
muscles
extend from
one vertebra to
another
• These muscles
are synergists
in extension
and rotation of
the spine
Muscles of Respiration
• The primary
function of deep
thoracic muscles is
to promote
movement for
breathing
• External
intercostals – more
superficial layer
that lifts the rib
cage and increases
thoracic volume to
allow inspiration
Muscles of Respiration
• Internal
intercostals –
deeper layer that
aids in forced
expiration
• Diaphragm – most
important muscle
in inspiration
Muscles of Respiration: The
Diaphragm
Muscles of the Abdominal Wall
• The abdominal wall is composed of four
paired muscles (internal and external
obliques, transversus abdominis, and
rectus abdominis), their fasciae, and their
aponeuroses
• Fascicles of these muscles run at right
and oblique angles to one another, giving
the abdominal wall added strength
Muscles of the Abdominal Wall
• In addition to forming the abdominal wall,
these muscles:
– Are involved with lateral flexion and rotation
of the trunk
– Help promote urination, defecation, childbirth,
vomiting, coughing, and screaming
Muscles of the Abdominal Wall
Muscles of the Abdominal Wall
Muscles of the Pelvic Floor (Pelvic
Diaphragm)
• The pelvic diaphragm is composed of two
paired muscles – levator ani and
coccygeus
• These muscles:
– Close the inferior outlet of the pelvis
– Support the pelvic floor
– Elevate the pelvic floor to help release feces
– Resist increased intra-abdominal pressure
Muscles of the Pelvic Floor: Pelvic
Diaphragm
Muscles of the Pelvic Floor
Two sphincter muscles allow voluntary
control of urination (sphincter urethrae) and
defecation (external anal sphincter)
Muscles of the Pelvic Floor
•The ischiocavernosus and bulbospongiosus
assist in erection of the penis and clitoris
Extrinsic Shoulder Muscles
• Muscles of the thorax
– Anterior: pectoralis major, pectoralis minor,
serratus anterior, and subclavius
– Posterior: latissimus dorsi, trapezius muscles,
levator scapulae, and rhomboids
– These muscles are involved with the
movements of the scapula including
elevation, depression, rotation, and lateral
and medial movements
• Prime movers of shoulder elevation are
the trapezius and levator scapulae
Extrinsic Shoulder Muscles
Extrinsic Shoulder Muscles
v
Muscles Crossing the Shoulder
• Nine muscles cross the shoulder joint and
insert into the humerus
• Prime movers include:
– Pectoralis major – arm flexion
– Latissimus dorsi and posterior fibers of the
deltoid – arm extension
– Middle fibers of the deltoid – arm abduction
Muscles Crossing the Shoulder
Muscles Crossing the Shoulder
Muscles Crossing the Shoulder
• Rotator cuff muscles – supraspinatus,
infraspinatus, teres minor, and
subscapularis
– Function mainly to reinforce the capsule of
the shoulder
– Secondarily act as synergists and fixators
• The coracobrachialis and teres major:
– Act as synergists
– Do not contribute to reinforcement of the
shoulder joint
Muscles Crossing the Shoulder
Muscles Crossing the Shoulder
Muscles Crossing the Elbow
• Forearm extension
– The triceps brachii is the prime mover of
forearm extension
– The anconeus is a weak synergist
• Forearm flexion
– Brachialis and biceps brachii are the chief
forearm flexors
– The brachioradialis acts as a synergist and
helps stabilize the elbow
Muscles of the Forearm
• The two functional forearm muscle groups are:
those that cause wrist movement, and those
that move the fingers and the thumb
• These muscles insert via strong ligaments
called flexor and extensor retinacula
• Most anterior muscles are flexors, and posterior
muscles are extensors
• The pronator teres and pronator quadratus are
not flexors, but pronate the forearm
• The supinator muscle is a synergist with the
biceps brachii in supinating the forearm
Muscles of the
Forearm:
Anterior
Compartment
• These muscles
are primarily
flexors of the
wrist and
fingers
Muscles of the Forearm: Anterior
Compartment
Muscles of
the Forearm:
Posterior
Compartment
• These
muscles are
primarily
extensors of
the wrist and
fingers
Figure 10.16a
Muscles of the
Forearm:
Posterior
Compartment
• These muscles
are primarily
extensors of the
wrist and fingers
Muscle Action of the Arm:
Summary
• The
posterior
extensor
and
anterior
flexor
muscles
are shown
Muscle Action of the Forearm:
Summary
• Posterior
extensors
of the wrist
and
fingers,
and
anterior
flexor
muscles
are shown
Intrinsic Muscles of the Hand
• These small muscles:
– Lie in the palm of the hand (none on the
dorsal side)
– Move the metacarpals and fingers
– Control precise movements (e.g., threading a
needle)
– Are the main abductors and adductors of the
fingers
– Produce opposition – move the thumb toward
the little finger
Intrinsic Muscles of the Hand
Intrinsic Muscles of the Hand
Finger and Thumb Movements
• Flexion
– Thumb – bends medially along the palm
– Fingers – bend anteriorly
• Extension
– Thumb – points laterally
– Fingers – move posteriorly
Intrinsic Muscles of the Hand:
Groups
• There are three groups of intrinsic hand
muscles
• The thenar eminence (ball of the thumb)
and hypothenar eminence (ball of the little
finger) – each have a flexor, an abductor,
and an opponens muscle
• The midpalm muscles, the lumbricals and
interossei, extend the fingers
• The interossei also abduct and adduct the
fingers
Intrinsic Muscles of the Hand:
Groups
Muscles Crossing Hip and Knee
Joints
• Most anterior compartment muscles of the
hip and thigh flex the femur at the hip and
extend the leg at the knee
• Posterior compartment muscles of the hip
and thigh extend the thigh and flex the leg
• The medial compartment muscles all
adduct the thigh
• These three groups are enclosed by the
fascia lata
Movements of the Thigh at the Hip:
Flexion and Extension
• The ball-and-socket hip joint permits flexion,
extension, abduction, adduction,
circumduction, and rotation
• The most important thigh flexors are the
iliopsoas (prime mover), tensor fasciae
latae, and rectus femoris
• The medially located adductor muscles and
sartorius assist in thigh flexion
Movements of the Thigh at the
Hip:
Flexion and Extension
• Thigh extension is primarily effected by
the hamstring muscles (biceps femoris,
semitendinosus, and semimembranosus)
• Forceful extension is aided by the gluteus
maximus
Movements
of the Thigh
at the Hip:
Flexion and
Extension
Movements of the Thigh at the
Hip:
Other Movements
• Abduction and rotation are effected by the
gluteus medius and gluteus minimus, and
are antagonized by the lateral rotators
• Thigh adduction is the role of five
adductor muscles (adductor magnus,
adductor longus, and adductor brevis; the
pectineus, and the gracilis)
Movements of the
Thigh at the Hip:
Other Movements
Movements of the Thigh at the Hip:
Other Movements
Movements of the Knee Joint
• The sole
extensor of the
knee is the
quadriceps
femoris
• The hamstring
muscles flex
the knee, and
are antagonists
to the
quadriceps
femoris
Fascia of the Leg
• A deep fascia of the
leg is continuous with
the fascia lata
• This fascia segregates
the leg into three
compartments:
anterior, lateral, and
posterior
• Distally, the fascia
thickens and forms the
flexor, extensor, and
fibular retinaculae
Figure 10.22a
Muscles of the Leg: Movements
• Various leg muscles produce the following
movements at the:
– Ankle – dorsiflexion and plantar flexion
– Intertarsal joints – inversion and eversion of
the foot
– Toes – flexion and extension
Muscles of the Anterior
Compartment
• These muscles are
the primary toe
extensors and
ankle dorsiflexors
• They include the
tibialis anterior,
extensor digitorum
longus, extensor
hallucis longus,
and fibularis tertius
Muscles of the
Anterior
Compartment
Muscles of the Lateral
Compartment
• These muscles
plantar flex and
evert the foot
• They include the
fibularis longus
and fibularis
brevis muscles
Muscles of the Lateral
Compartment
Muscles of the Posterior
Compartment
• These muscles
primarily flex the
foot and the toes
• They include the
gastrocnemius,
soleus, tibialis
posterior, flexor
digitorum longus,
and flexor hallucis
longus
Muscles of the Posterior
Compartment
Muscles of
the Posterior
Compartment
Muscle Actions of the Thigh:
Summary
• Thigh muscles:
– Flex and extend the thigh (posterior
compartment)
– Extend the leg (anterior compartment)
– Adduct the thigh (medial compartment)
Muscle Actions of the Thigh:
Summary
Muscle Actions of the Leg:
Summary
• Leg muscles:
– Plantar flex and evert the foot (lateral
compartment)
– Plantar flex the foot and flex the toes
(posterior compartment)
– Dorsiflex the foot and extend the toes
(anterior compartment)
Muscle Actions of the Leg:
Summary
Intrinsic Muscles of the Foot
• These muscles help flex, extend, abduct,
and adduct the toes
• In addition, along with some leg tendons,
they support the arch of the foot
• There is a single dorsal foot muscle, the
extensor digitorum brevis, which extends
the toes
• The plantar muscles occur in four layers
Plantar Muscles: First Layer
(Superficial)
• Superficial muscles
of the plantar
aspect of the foot
• These muscles are
similar to the
corresponding
muscles of the
hand
Plantar
Muscles:
Second Layer
Plantar
Muscles:
Third Layer
Plantar Muscles: Fourth Layer