General doctrine about muscles

The Department of Human anatomyThe Department of Human anatomy
General doctrineGeneral doctrine
about the muscles.about the muscles.

PLANPLAN
 General doctrine about of muscles.General doctrine about of muscles.
Smooth and skeletal muscles, theirSmooth and skeletal muscles, their
development and structure.development and structure.
 Muscles as an organ.Muscles as an organ.
 Classification of muscles depending onClassification of muscles depending on
the form, arrangement and functions,the form, arrangement and functions,
their outset and fixation. Tendons andtheir outset and fixation. Tendons and
aponeurosis.aponeurosis.
 Auxiliary apparatus of muscles.Auxiliary apparatus of muscles.

The term “muscle” is derived from Latin wordThe term “muscle” is derived from Latin word
“Musculus” diminutive of “mus” meaning“Musculus” diminutive of “mus” meaning
mouse. They were named so because theirmouse. They were named so because their
belly resembles body of the mouse and theirbelly resembles body of the mouse and their
tendons resemble mouse’s tail.tendons resemble mouse’s tail.
Muscles are contractile tissues that bring aboutMuscles are contractile tissues that bring about
movements of different body parts. They canmovements of different body parts. They can
be regarded as motors of human bodybe regarded as motors of human body
because they provide all the force necessarybecause they provide all the force necessary
to perform different types of movements.to perform different types of movements.

Types of muscles:Types of muscles:
Muscles are of three types; skeletalMuscles are of three types; skeletal
(striated), smooth (non-striated) and(striated), smooth (non-striated) and
cardiac.cardiac.

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Skeletal Muscles:Skeletal Muscles:
 They are also known as striped, striated,They are also known as striped, striated,
somatic and voluntary musclessomatic and voluntary muscles
 They are the most abundant type and are foundThey are the most abundant type and are found
attached to the skeleton. For this reason theyattached to the skeleton. For this reason they
are called skeletal muscles.are called skeletal muscles.
 They are innervated by somatic nervous systemThey are innervated by somatic nervous system
and are therefore under voluntary control. Theyand are therefore under voluntary control. They
obey the will of human beings.obey the will of human beings.
 They respond quickly to stimuli and are capableThey respond quickly to stimuli and are capable
of rapid contractions. They get fatigued easilyof rapid contractions. They get fatigued easily
because of their rapiditybecause of their rapidity
 Each muscle fiber is multinucleated cylindricalEach muscle fiber is multinucleated cylindrical
cell containing groups of myofibrils. Thecell containing groups of myofibrils. The
myofibrils are in turn made up of myofilamentsmyofibrils are in turn made up of myofilaments
of three types namely actin, myosin, andof three types namely actin, myosin, and
tropomyosin. Thus the skeletal muscles havetropomyosin. Thus the skeletal muscles have
three structural levels namely muscle fibers,three structural levels namely muscle fibers,
myofibrils and myofilaments.myofibrils and myofilaments.
 Examples of skeletal muscles include allExamples of skeletal muscles include all
muscles of body wall.muscles of body wall.

Smooth muscles:Smooth muscles:
 They are also known as plain, unstriped, visceralThey are also known as plain, unstriped, visceral
and involuntary muscles.and involuntary muscles.
 Unlike skeletal muscles, they do not exhibitUnlike skeletal muscles, they do not exhibit
cross striations under the microscope and thuscross striations under the microscope and thus
they got the name “smooth”.they got the name “smooth”.
 They are supplied by autonomic nervous systemThey are supplied by autonomic nervous system
and therefore they are involuntary in their action.and therefore they are involuntary in their action.
They do not obey the will of human being.They do not obey the will of human being.
 They respond slowly to stimuli but are capableThey respond slowly to stimuli but are capable
of long time sustained contractions. They do notof long time sustained contractions. They do not
get fatigued easily because of their slowness ofget fatigued easily because of their slowness of
response.response.
 They provide motor power for regulating internalThey provide motor power for regulating internal
environment related to digestion, circulation,environment related to digestion, circulation,
secretion and excretion.secretion and excretion.
 Each smooth muscle fiber is an elongatedEach smooth muscle fiber is an elongated
spindle shaped cell with a single nucleus placedspindle shaped cell with a single nucleus placed
at the center. They also possess actin andat the center. They also possess actin and
myosin filaments but the structural arrangementmyosin filaments but the structural arrangement
of these filaments is very different as comparedof these filaments is very different as compared
to the skeletal muscles.to the skeletal muscles.
 Examples of smooth muscles include musclesExamples of smooth muscles include muscles
of blood vessels, and muscles of the gut etc.of blood vessels, and muscles of the gut etc.

Cardiac muscles:Cardiac muscles:
 They form the myocardium of humanThey form the myocardium of human
heart.heart.
 Cardiac muscle is intermediate inCardiac muscle is intermediate in
structure lying between the skeletal andstructure lying between the skeletal and
smooth muscles. They are striated likesmooth muscles. They are striated like
skeletal muscles but at the same time theyskeletal muscles but at the same time they
are involuntary and have uninuclear cellsare involuntary and have uninuclear cells
like smooth muscles.like smooth muscles.
 They are meant for automatic rhythmicThey are meant for automatic rhythmic
contractions for long period of time.contractions for long period of time.
 Each muscle fiber has a single centrallyEach muscle fiber has a single centrally
placed nucleus. The fibers branch andplaced nucleus. The fibers branch and
anastomoses with each other to form aanastomoses with each other to form a
syncitium. Neighboring cells are joined bysyncitium. Neighboring cells are joined by
intercalated discs which provideintercalated discs which provide
conductive pathways from one cell toconductive pathways from one cell to
another.another.

Functions of Muscular System:Functions of Muscular System:
Muscular system has the following importantMuscular system has the following important
functions in human body;functions in human body;
 MOVEMENTS OF BODY PARTSMOVEMENTS OF BODY PARTS
 STABILITY AND POSTURESTABILITY AND POSTURE
 HEAT PRODUCTIONHEAT PRODUCTION
 CIRCULATIONCIRCULATION
 HELP IN DIGESTIONHELP IN DIGESTION

 MOVEMENTS OF BODY PARTS:MOVEMENTS OF BODY PARTS: Skeletal muscles are responsible Skeletal muscles are responsible
for all voluntary movements of human body parts. Muscles are for all voluntary movements of human body parts. Muscles are
motors of body where chemical energy of food is converted into motors of body where chemical energy of food is converted into
mechanical work.mechanical work.
 WorkWork
 MimicMimic

 STABILITY AND POSTURE:STABILITY AND POSTURE: Skeletal muscles Skeletal muscles
stabilize human skeleton and give a proper posture to stabilize human skeleton and give a proper posture to
human beings. human beings.

 ArticulationArticulation
 RespirationRespiration

 HEAT PRODUCTION:HEAT PRODUCTION: A large share of body’s energy is used by A large share of body’s energy is used by
muscular system. As a result of high metabolic rate, muscles muscular system. As a result of high metabolic rate, muscles
produce great amount of heat in the body. Heat produced by produce great amount of heat in the body. Heat produced by
muscles is very important in cold climates.muscles is very important in cold climates.
 CIRCULATION:CIRCULATION: Cardiac muscles Cardiac muscles
provide the main force for circulation provide the main force for circulation
of blood throughout human body. The of blood throughout human body. The
regular pumping of heart keeps the regular pumping of heart keeps the
blood in motion and nutrients are blood in motion and nutrients are
readily available to every tissue of readily available to every tissue of
human body.human body.

 HELP IN DIGESTION:HELP IN DIGESTION: Smooth muscles of organs like Smooth muscles of organs like
stomach and intestine help the digestive system in the stomach and intestine help the digestive system in the
process of digestion of food.process of digestion of food.

A typical skeletal muscle consists ofA typical skeletal muscle consists of
two ends and two parts.two ends and two parts.
Ends:Ends:
 Origin is one end of the muscleOrigin is one end of the muscle
which remains fixed during itswhich remains fixed during its
contraction.contraction.
 Insertion is the other end whichInsertion is the other end which
moves during its contraction. Inmoves during its contraction. In
the limb muscles, the origin isthe limb muscles, the origin is
usually proximal to insertion.usually proximal to insertion.
Parts:Parts:
 Fleshy part is contractile, and isFleshy part is contractile, and is
called the ‘belly’.called the ‘belly’.
 Fibrous part is non-contractileFibrous part is non-contractile
and inelastic. When cord-like orand inelastic. When cord-like or
rope-like, it is called tendon;rope-like, it is called tendon;
when flattened, it is calledwhen flattened, it is called

A typical skeletal muscle consists of two types of A typical skeletal muscle consists of two types of
tissues: Contractile tissue and Supporting tissues: Contractile tissue and Supporting
tissue.tissue.
 The contractile tissue of each muscle is The contractile tissue of each muscle is
composed of numerous muscle fibers. Each composed of numerous muscle fibers. Each
muscle fiber is a multinucleated, cross-striated muscle fiber is a multinucleated, cross-striated
cylindrical cell. The length of each muscle fiber cylindrical cell. The length of each muscle fiber
is between 1 and 300 mm. It consists of a cell is between 1 and 300 mm. It consists of a cell
membrane (sarcolemma), which encloses the membrane (sarcolemma), which encloses the
cytoplasm (sarcoplasm).cytoplasm (sarcoplasm).

There are two types of substances embedded in theThere are two types of substances embedded in the
sarcoplasm.sarcoplasm.
 Several nuclei arranged at the periphery beneath theSeveral nuclei arranged at the periphery beneath the
sarcolemma.sarcolemma.
 A number of evenly distributed longitudinal threadsA number of evenly distributed longitudinal threads
called myofibrils.called myofibrils.
Each myofibril shows alternate light and dark bands.Each myofibril shows alternate light and dark bands.
Dark bands are Anisotropic and thus are known as A-Dark bands are Anisotropic and thus are known as A-
bands. The light bands are Isotropic and thus arebands. The light bands are Isotropic and thus are
known as I-bands. The bands of adjacent fibrils areknown as I-bands. The bands of adjacent fibrils are
aligned transversely so that the muscle fiber appearsaligned transversely so that the muscle fiber appears
cross striated. In the middles of the A band (darkcross striated. In the middles of the A band (dark
band) there is a light H band. In the middle of the Hband) there is a light H band. In the middle of the H
band there is a dark M line. In the middle of the I bandband there is a dark M line. In the middle of the I band
(light band) there is a dark Z disk also known as(light band) there is a dark Z disk also known as
Krause’s membrane. The segment of myofibrilKrause’s membrane. The segment of myofibril
between two Z discs is called sarcomere.between two Z discs is called sarcomere.

General doctrine about muscles

Supporting tissue:Supporting tissue:
It helps in organization of the muscle.It helps in organization of the muscle.
EndomysiumEndomysium  surrounds each musclesurrounds each muscle
fiber separately.fiber separately. PerimysiumPerimysium  surroundssurrounds
bundles (fasciculi or myonemes) ofbundles (fasciculi or myonemes) of
muscle fibers of various sizes.muscle fibers of various sizes.
EpimysiumEpimysium  surrounds the entire muscle.surrounds the entire muscle.
The connective tissue of the muscleThe connective tissue of the muscle
becomes continuous with the tendon.becomes continuous with the tendon.

Tendons and aponeurosesTendons and aponeuroses
On the ends, muscular connective tissueOn the ends, muscular connective tissue
elements continue as tendons, which serve forelements continue as tendons, which serve for
the attachment of the muscle. Tendons arethe attachment of the muscle. Tendons are
light golden in color, rather strong, and highlylight golden in color, rather strong, and highly
resistant to extension. They are made of denseresistant to extension. They are made of dense
regular connective tissue, which consists ofregular connective tissue, which consists of
the cells — fibroblasts and numerous parallelthe cells — fibroblasts and numerous parallel
collagen fibers that interweave and contributecollagen fibers that interweave and contribute
to most of the tendon's mass.to most of the tendon's mass.
Wide and flat tendons are calledWide and flat tendons are called aponeuroses.aponeuroses.
Their structure is characterized by theTheir structure is characterized by the
distribution of collagen fibers in one plane.distribution of collagen fibers in one plane.
However, collagen fibers are orientated alongHowever, collagen fibers are orientated along
the direction of stretching forces acting on thethe direction of stretching forces acting on the

The fibers of the skeletal muscles of theThe fibers of the skeletal muscles of the
entire body are not same. There are twoentire body are not same. There are two
primary variants, which differ from oneprimary variants, which differ from one
another significantly. These variants are:another significantly. These variants are:
 Slow (Type I) muscle fibersSlow (Type I) muscle fibers
 Fast (Type II) muscle fibersFast (Type II) muscle fibers
Type IIa fibersType IIa fibers
Type IIb fibersType IIb fibers

Slow (Type I) muscle fibers:Slow (Type I) muscle fibers:
These type of fibers show a slow ‘tonic’These type of fibers show a slow ‘tonic’
contraction characteristic of posturalcontraction characteristic of postural
muscles. These are red in color becausemuscles. These are red in color because
of large amounts of myoglobin, Theof large amounts of myoglobin, The
fibers are rich in mitochondria andfibers are rich in mitochondria and
oxidative enzymes, but poor inoxidative enzymes, but poor in
phosphorylases. Because of a well-phosphorylases. Because of a well-
developed aerobic metabolism, slowdeveloped aerobic metabolism, slow
fibers are highly resistant to fatigue.fibers are highly resistant to fatigue.

Fast (Type II) muscle fibers:Fast (Type II) muscle fibers:
Type II muscle fibers are further divided into twoType II muscle fibers are further divided into two
categories: Type IIa and Type IIb.categories: Type IIa and Type IIb.
Type IIa fibers:Type IIa fibers:
 They represent a variant of type II (fast) fibersThey represent a variant of type II (fast) fibers
which are relatively resistant to fatigue, althoughwhich are relatively resistant to fatigue, although
less than type I fibers. They are red in colorless than type I fibers. They are red in color
because of presence of significant amount ofbecause of presence of significant amount of
myoglobin in them. Oxidative phosphorylation inmyoglobin in them. Oxidative phosphorylation in
this type of fibers is more developed that Type Ithis type of fibers is more developed that Type I
fibers.fibers.

Type IIb fibers:Type IIb fibers:
 They show a fast ‘phasic’ contraction,They show a fast ‘phasic’ contraction,
required for large-scale movements ofrequired for large-scale movements of
body segments. These are paler (white) inbody segments. These are paler (white) in
color because of small amounts ofcolor because of small amounts of
myoglobin. The fibers are rich in glycogenmyoglobin. The fibers are rich in glycogen
and phosphorylases, but poor inand phosphorylases, but poor in
mitochondria and oxidative enzymes.mitochondria and oxidative enzymes.
Because of a glycolytic respiration, the fastBecause of a glycolytic respiration, the fast
fibers are quite easily fatigued.fibers are quite easily fatigued.

The muscles have been named in a number ofThe muscles have been named in a number of
ways.ways.
 According to theirAccording to their shapeshape, e.g. trapezius,, e.g. trapezius,
rhomboideus, serratus anterior, latissimus dorsi,rhomboideus, serratus anterior, latissimus dorsi,
etc.etc.
 According to theAccording to the number of heads of originnumber of heads of origin, e.g., e.g.
biceps, triceps, quadriceps, digastric, etc.biceps, triceps, quadriceps, digastric, etc.
 According to theirAccording to their gross structuregross structure, e.g., e.g.
semitendinosus, semi-’membranosus, etc.semitendinosus, semi-’membranosus, etc.
 According to theirAccording to their locationlocation, e.g. temporalis, supra-, e.g. temporalis, supra-
spinatus, intercostales.spinatus, intercostales.

 According to theirAccording to their attachmentsattachments, e.g. stylohyoid,, e.g. stylohyoid,
cricothyroid, etc.cricothyroid, etc.
 According to theirAccording to their actionaction, e.g. adductor longus,, e.g. adductor longus,
flexor carpi ulnaris, abductor pollicis longus, etc.flexor carpi ulnaris, abductor pollicis longus, etc.
 According to direction of theirAccording to direction of their fibersfibers, e.g. rectus, e.g. rectus
abdominis, transversus abdominis, orbicularisabdominis, transversus abdominis, orbicularis
oculi.oculi.
 A muscle with two bellies with an interveningA muscle with two bellies with an intervening
tendon is called digastric muscle. Muscle withtendon is called digastric muscle. Muscle with
number of intervening tendons or intersections isnumber of intervening tendons or intersections is
the rectus abdominis.the rectus abdominis.
 Depending on the type of action produced by theDepending on the type of action produced by the
muscle on the joint there uni-articular, bi-articularmuscle on the joint there uni-articular, bi-articular
and multi-articular muscles.and multi-articular muscles.

According toAccording to embryonicembryonic
development:development:
- Autochthonous- Autochthonous
remain in the place of theirremain in the place of their
formation and do notformation and do not
relocate to other regionsrelocate to other regions
Autochthonous musclesAutochthonous muscles
comprise the deepcomprise the deep
muscles of the back,muscles of the back,
intercostal muscles, andintercostal muscles, and
abdominal muscles asabdominal muscles as
well as the majority of thewell as the majority of the
muscles of the limbs,muscles of the limbs,
neck, and headneck, and head
-- HeterochthonousHeterochthonous
move from the place ofmove from the place of
their embryologicaltheir embryological
origin to other regionsorigin to other regions
 truncipetal musclestruncipetal muscles,,
which migrate to thewhich migrate to the
trunk from their origin ontrunk from their origin on
the upper and lowerthe upper and lower
limbs;limbs;
 truncifugal musclestruncifugal muscles,,
which migrate to thewhich migrate to the
limbs in the process oflimbs in the process of
development.development.

THE WORK OF MUSCLESTHE WORK OF MUSCLES
 During contraction, the skeletal muscles shortenDuring contraction, the skeletal muscles shorten
to 30-40% of their original length. This causesto 30-40% of their original length. This causes
two points, where the muscles attach, to movetwo points, where the muscles attach, to move
closer towards each other. In the process ofcloser towards each other. In the process of
contraction, muscles carry out certain work .contraction, muscles carry out certain work .
 When the muscle contracts, in most cases oneWhen the muscle contracts, in most cases one
end of the muscle remains fixedend of the muscle remains fixed (punctum(punctum
fixum),fixum), whereas the other end moveswhereas the other end moves (punctum(punctum
mobile)mobile) pulling the bone to which it is attached.pulling the bone to which it is attached.
Depending on the character of movement, theseDepending on the character of movement, these
points may switch places.points may switch places.

There are too many diseases that effect the muscularThere are too many diseases that effect the muscular
system to mention. Many of them are brain disorderssystem to mention. Many of them are brain disorders
that effect the motor control areas in the frontal andthat effect the motor control areas in the frontal and
parietal lobes of the brain. To name some:parietal lobes of the brain. To name some:
 Muscular dystrophy - genetic disease that rendersMuscular dystrophy - genetic disease that renders
muscle fibres more vulnerable to damage than normalmuscle fibres more vulnerable to damage than normal
 Dermatomyositis - autoimmune disease causing skinDermatomyositis - autoimmune disease causing skin
rash and muscle weaknessrash and muscle weakness
 Compartment Syndrome - the result of too muchCompartment Syndrome - the result of too much
pressure building up around the muscles causingpressure building up around the muscles causing
severe pain and sometimes cellular deathsevere pain and sometimes cellular death
 Rhabdomyolysis - causes muscle fibbers toRhabdomyolysis - causes muscle fibbers to
breakdown and get absorbed into the bloodstream,breakdown and get absorbed into the bloodstream,
alcoholism, drug abuse, and heatstroke are severalalcoholism, drug abuse, and heatstroke are several
known causesknown causes
 Fibrodysplasia Ossificans Progressia - rare congenitalFibrodysplasia Ossificans Progressia - rare congenital
disease that causes the muscles, tendons, anddisease that causes the muscles, tendons, and
ligaments to be replaced with bone tissueligaments to be replaced with bone tissue

If you want to keep your muscles systemIf you want to keep your muscles system
healthy you should:healthy you should:
-- Exercise on a regular basisExercise on a regular basis
- Eat a balanced diet- Eat a balanced diet
- Consume a sufficient amount of Vitamin E- Consume a sufficient amount of Vitamin E

Thank you for attention!Thank you for attention!

General doctrine about muscles

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General doctrine about muscles