The Department of Human anatomyThe Department of Human anatomy

General doctrine General doctrine about the muscles.about the muscles.

PLANPLAN General doctrine about of muscles. General doctrine about of muscles.

Smooth and skeletal muscles, their Smooth and skeletal muscles, their development and structure.development and structure.

Muscles as an organ. Muscles as an organ. Classification of muscles depending on Classification of muscles depending on

the form, arrangement and functions, the form, arrangement and functions, their outset and fixation. Tendons and their outset and fixation. Tendons and aponeurosis. aponeurosis.

Auxiliary apparatus of muscles.Auxiliary apparatus of muscles.

The term “muscle” is derived from Latin word The term “muscle” is derived from Latin word “Musculus” diminutive of “mus” meaning “Musculus” diminutive of “mus” meaning mouse. They were named so because their mouse. They were named so because their belly resembles body of the mouse and their belly resembles body of the mouse and their tendons resemble mouse’s tail. tendons resemble mouse’s tail.

Muscles are contractile tissues that bring about Muscles are contractile tissues that bring about movements of different body parts. They can movements of different body parts. They can be regarded as motors of human body be regarded as motors of human body because they provide all the force necessary because 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; skeletal Muscles are of three types; skeletal

(striated), smooth (non-striated) and (striated), smooth (non-striated) and cardiac. cardiac.

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 found They are the most abundant type and are found

attached to the skeleton. attached to the skeleton. For this reason they For this reason they are called skeletal muscles.are called skeletal muscles.

They are innervated by somatic nervous They are innervated by somatic nervous system and are therefore under voluntary system and are therefore under voluntary control. control. They obey the will of human beings.They obey the will of human beings.

They respond quickly to stimuli and are capable They respond quickly to stimuli and are capable of rapid contractions. of rapid contractions. They get fatigued easily They get fatigued easily because of their rapiditybecause of their rapidity

Each muscle fiber is multinucleated cylindrical Each muscle fiber is multinucleated cylindrical cell containing groups of myofibrils. The cell containing groups of myofibrils. The myofibrils are in turn made up of myofilaments myofibrils are in turn made up of myofilaments of three types namely actin, myosin, and of three types namely actin, myosin, and tropomyosin. Thus the skeletal muscles have tropomyosin. 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 all Examples of skeletal muscles include all muscles of body wall.muscles of body wall.

Smooth muscles:Smooth muscles: They are also known as plain, unstriped, visceral They are also known as plain, unstriped, visceral

and involuntary muscles.and involuntary muscles. Unlike skeletal muscles, they do not exhibit Unlike skeletal muscles, they do not exhibit

cross striations under the microscope and thus cross striations under the microscope and thus they got the name “smooth”.they got the name “smooth”.

They are supplied by autonomic nervous system They 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 capable of They respond slowly to stimuli but are capable of long time sustained contractions. They do not long time sustained contractions. They do not get fatigued easily because of their slowness of get fatigued easily because of their slowness of response.response.

They provide motor power for regulating internal They 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 elongated Each smooth muscle fiber is an elongated spindle shaped cell with a single nucleus placed spindle shaped cell with a single nucleus placed at the center. They also possess actin and at the center. They also possess actin and myosin filaments but the structural arrangement myosin filaments but the structural arrangement of these filaments is very different as compared of these filaments is very different as compared to the skeletal muscles.to the skeletal muscles.

Examples of smooth muscles include muscles of Examples of smooth muscles include muscles of blood vessels, and muscles of the gut etc.blood vessels, and muscles of the gut etc.

Cardiac muscles:Cardiac muscles:

They form the myocardium of human They form the myocardium of human heart.heart.

Cardiac muscle is intermediate in Cardiac muscle is intermediate in structure lying between the skeletal and structure lying between the skeletal and smooth muscles. They are striated like smooth muscles. They are striated like skeletal muscles but at the same time they skeletal muscles but at the same time they are involuntary and have uninuclear cells are involuntary and have uninuclear cells like smooth muscles.like smooth muscles.

They are meant for automatic rhythmic They are meant for automatic rhythmic contractions for long period of time.contractions for long period of time.

Each muscle fiber has a single centrally Each muscle fiber has a single centrally placed nucleus. The fibers branch and placed nucleus. The fibers branch and anastomoses with each other to form a anastomoses with each other to form a syncitium. Neighboring cells are joined by syncitium. Neighboring cells are joined by intercalated discs which provide intercalated discs which provide conductive pathways from one cell to conductive pathways from one cell to another.another.

Functions of Muscular System:Functions of Muscular System:

Muscular system has the following important Muscular 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. for all voluntary movements of human body parts. MMuscles are uscles 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 hearegular pumping of hearrt keeps the t 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 of A typical skeletal muscle consists of two ends and two parts.two ends and two parts.

Ends:Ends: Origin is one end of the muscle Origin is one end of the muscle

which remains fixed during its which remains fixed during its contraction.contraction.

Insertion is the other end which Insertion is the other end which moves during its contraction. In moves during its contraction. In the limb muscles, the origin is the limb muscles, the origin is usually proximal to insertion.usually proximal to insertion.

Parts:Parts: Fleshy part is contractile, and is Fleshy part is contractile, and is

called the ‘belly’.called the ‘belly’. Fibrous part is non-contractile Fibrous part is non-contractile

and inelastic. When cord-like or and inelastic. When cord-like or rope-like, it is called tendon; rope-like, it is called tendon; when flattened, it is called when flattened, it is called aponeurosis.aponeurosis.

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 the There are two types of substances embedded in the sarcoplasm.sarcoplasm.

Several nuclei arranged at the periphery beneath the Several nuclei arranged at the periphery beneath the sarcolemma.sarcolemma.

A number of evenly distributed longitudinal threads A 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 are bands. The light bands are Isotropic and thus are known as I-bands. The bands of adjacent fibrils are known as I-bands. The bands of adjacent fibrils are aligned transversely so that the muscle fiber appears aligned transversely so that the muscle fiber appears cross striated. In the middles of the A band (dark cross striated. In the middles of the A band (dark band) there is a light H band. In the middle of the H band) 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 band band 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 myofibril Krause’s membrane. The segment of myofibril between two Z discs is called sarcomere.between two Z discs is called sarcomere.

Supporting tissue:Supporting tissue:

It helps in organization of the muscle. It helps in organization of the muscle. EndomysiumEndomysium  surrounds each muscle surrounds each muscle fiber separately. fiber separately. PerimysiumPerimysium  surrounds surrounds bundles (fasciculi or myonemes) of bundles (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 muscle The connective tissue of the muscle becomes continuous with the tendon.becomes continuous with the tendon.

TendonsTendons and aponeuroses and aponeuroses On the ends, muscular connective tissue On the ends, muscular connective tissue

elements continue as tendons, which serve for elements continue as tendons, which serve for the attachment of the muscle. Tendons are the attachment of the muscle. Tendons are light golden in color, rather strong, and highly light golden in color, rather strong, and highly resistant to extension. They are made of dense resistant to extension. They are made of dense regular connective tissue, which consists of regular connective tissue, which consists of the cells — fibroblasts and numerous parallel the cells — fibroblasts and numerous parallel collagen fibers that interweave and contribute collagen fibers that interweave and contribute to most of the tendon's mass.to most of the tendon's mass.

Wide and flat tendons are called Wide and flat tendons are called aponeuroses.aponeuroses. Their structure is characterized by the Their structure is characterized by the distribution of collagen fibers in one plane. distribution of collagen fibers in one plane. However, collagen fibers are orientated along However, collagen fibers are orientated along the direction of stretching forces acting on the the direction of stretching forces acting on the aponeurosis.aponeurosis.

The fibers of the skeletal muscles of the The fibers of the skeletal muscles of the entire body are not same. There are two entire body are not same. There are two primary variants, which differ from one primary 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 postural contraction characteristic of postural muscles. These are red in color because muscles. These are red in color because of large amounts of myoglobin, The of large amounts of myoglobin, The fibers are rich in mitochondria and fibers are rich in mitochondria and oxidative enzymes, but poor in oxidative enzymes, but poor in phosphorylases.  Because of a well-phosphorylases.  Because of a well-developed aerobic metabolism, slow developed 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 two Type 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) fibers They represent a variant of type II (fast) fibers

which are relatively resistant to fatigue, although which are relatively resistant to fatigue, although less than type I fibers. They are red in color less than type I fibers. They are red in color because of presence of significant amount of because of presence of significant amount of myoglobin in them. Oxidative phosphorylation in myoglobin in them. Oxidative phosphorylation in this type of fibers is more developed that Type I this 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 of required for large-scale movements of body segments. These are paler (white) in body segments. These are paler (white) in color because of small amounts of color because of small amounts of myoglobin. The fibers are rich in glycogen myoglobin. The fibers are rich in glycogen and phosphorylases, but poor in and phosphorylases, but poor in mitochondria and oxidative enzymes. mitochondria and oxidative enzymes. Because of a glycolytic respiration, the fast Because of a glycolytic respiration, the fast fibers are quite easily fatigued.fibers are quite easily fatigued.

The muscles have been named in a number of The muscles have been named in a number of ways.ways.

According to their According to their shapeshape, e.g. trapezius, , e.g. trapezius, rhomboideus, serratus anterior, latissimus dorsi, rhomboideus, serratus anterior, latissimus dorsi, etc.etc.

According to the According 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 their According to their gross structuregross structure, e.g. , e.g. semitendinosus, semi-’membranosus, etc.semitendinosus, semi-’membranosus, etc.

According to their According to their locationlocation, e.g. temporalis, supra-, e.g. temporalis, supra-spinatus, intercostales.spinatus, intercostales.

According to their According to their attachmentsattachments, e.g. stylohyoid, , e.g. stylohyoid, cricothyroid, etc.cricothyroid, etc.

According to their According 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 their According to direction of their fibersfibers, e.g. rectus , e.g. rectus abdominis, transversus abdominis, orbicularis abdominis, transversus abdominis, orbicularis oculi.oculi.

A muscle with two bellies with an intervening A muscle with two bellies with an intervening tendon is called digastric muscle. Muscle with tendon is called digastric muscle. Muscle with number of intervening tendons or intersections is number of intervening tendons or intersections is the rectus abdominis.the rectus abdominis.

Depending on the type of action produced by the Depending on the type of action produced by the muscle on the joint there uni-articular, bi-articular muscle on the joint there uni-articular, bi-articular and multi-articular muscles.and multi-articular muscles.

According to According to embryonic embryonic development:development:- Autochthonous- Autochthonous

remain in the place of their remain in the place of their formation and do not formation and do not relocate to other regionsrelocate to other regions

Autochthonous muscles Autochthonous muscles comprise the deep comprise the deep muscles of the back, muscles of the back, intercostal muscles, and intercostal muscles, and abdominal muscles as abdominal muscles as well as the majority of the well as the majority of the muscles of the limbs, muscles of the limbs, neck, and headneck, and head

- - HeterochthonousHeterochthonous

move from the place of move from the place of their embryological their embryological origin to other regionsorigin to other regions

truncipetal musclestruncipetal muscles, , which migrate to the which migrate to the trunk from their origin on trunk from their origin on the upper and lower the upper and lower limbs;limbs;

truncifugal musclestruncifugal muscles, , which migrate to the which migrate to the limbs in the process of limbs in the process of development.development.

THE WORK OF MUSCLESTHE WORK OF MUSCLES During contraction, the skeletal muscles shorten During contraction, the skeletal muscles shorten

to 30-40% of their original length. This causes to 30-40% of their original length. This causes two points, where the muscles attach, to move two points, where the muscles attach, to move closer towards each other. In the process of closer 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 one When 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 moves whereas 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, these Depending on the character of movement, these points may switch places.points may switch places.

TThere are too many diseases that effect the muscular here are too many diseases that effect the muscular system to mention.  Many of them are brain disorders system to mention.  Many of them are brain disorders that effect the motor control areas in the frontal and that 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 renders Muscular dystrophy - genetic disease that renders muscle fibres more vulnerable to damage than normalmuscle fibres more vulnerable to damage than normal

Dermatomyositis - autoimmune disease causing skin Dermatomyositis - autoimmune disease causing skin rash and muscle weaknessrash and muscle weakness

Compartment Syndrome - the result of too much Compartment Syndrome - the result of too much pressure building up around the muscles causing pressure building up around the muscles causing severe pain and sometimes cellular deathsevere pain and sometimes cellular death

Rhabdomyolysis - causes muscle fibbers to Rhabdomyolysis - causes muscle fibbers to breakdown and get absorbed into the bloodstream, breakdown and get absorbed into the bloodstream, alcoholism, drug abuse, and heatstroke are several alcoholism, drug abuse, and heatstroke are several known causesknown causes

Fibrodysplasia Ossificans Progressia - rare congenital Fibrodysplasia Ossificans Progressia - rare congenital disease that causes the muscles, tendons, and disease 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 system If 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 dietEat a balanced diet- - Consume  a sufficient amount of Vitamin EConsume  a sufficient amount of Vitamin E

Thank you for attention!Thank you for attention!