MUSCLE MUSCLE

TISSUETISSUE

MyologyMyology Anatomical study of muscles is called myologyAnatomical study of muscles is called myology Mostly myology is concerned with skeletal musclesMostly myology is concerned with skeletal muscles Together with bones, joints, tendons and Together with bones, joints, tendons and

ligaments, they form the ligaments, they form the musclosketal system musclosketal system of of levers that provide body movementslevers that provide body movements

The musculosketal system work closely together The musculosketal system work closely together with the nervous system to attain a coordinated with the nervous system to attain a coordinated and meaningful body movements. and meaningful body movements.

Types of MusclesTypes of Muscles

Skeletal muscleSkeletal muscle-attached to bones-attached to bones-striated-striated-voluntary-voluntary-cylindrical-cylindrical-multinucleate & peripheral-multinucleate & peripheral

Types of Muscles...Types of Muscles...

Smooth muscleSmooth muscle -visceral organs of GIT, -visceral organs of GIT,

-blood vessels etc-blood vessels etc -non-striated, -non-striated, -involuntary-involuntary -spindle-shaped, -spindle-shaped, -uninucleate-uninucleate

Types of Muscles...Types of Muscles...

Cardiac muscleCardiac muscle--heart (myocardium)heart (myocardium)-striated-striated-involuntary-involuntary-branched -branched -intercalated discs-intercalated discs

Muscle FunctionsMuscle Functions

MovementMovementMaintain postureMaintain postureStabilize jointsStabilize jointsHeat productionHeat production

Characteristics of Muscle Characteristics of Muscle TissueTissue

Excitable (+ neuron, adipocytes)Excitable (+ neuron, adipocytes)-response to electrical impulses-response to electrical impulses

ContractileContractile-shorten and lengthen to generate-shorten and lengthen to generatemechanical energymechanical energy

Elongated cellsElongated cells

TerminologyTerminologyHas special terminologyHas special terminology Muscle cell= myofibre or myocyteMuscle cell= myofibre or myocyte Myofibrils= contractile elementsMyofibrils= contractile elements Myofilaments= actin and myosinMyofilaments= actin and myosin Sarcoplasm= muscle cytoplasmSarcoplasm= muscle cytoplasm Sarcoplasmic reticulum= muscle ERSarcoplasmic reticulum= muscle ER Sarcomere= contractile unit/segmentSarcomere= contractile unit/segment Sarcolemma= cell membrane/ Sarcolemma= cell membrane/

plasmalemmaplasmalemma Sarcosome= mitochondria (rare use)Sarcosome= mitochondria (rare use)

Skeletal muscles cellsSkeletal muscles cells -Connective tissue wrappings (well developed in skeletal -Connective tissue wrappings (well developed in skeletal

muscles)muscles)

EndomysiumEndomysium- Loose areolar and elastic fibres cover - Loose areolar and elastic fibres cover

individual myofibresindividual myofibres PerimysiumPerimysium -Collagen fibre fascicule (a bundle of muscle cells)-Collagen fibre fascicule (a bundle of muscle cells) EpimysiumEpimysium -Dense fibrous connective around entire muscle-Dense fibrous connective around entire muscle

Fig. Muscle organization

Fig. Myofibre

Fig. Sarcomere

Fig. Myofibril organization

Actin (thin filaments)

Fig. Myosin (thick filament)

Fig. Skeletal muscle fibre- H/E

Slow twitch (red) fibersSlow twitch (red) fibers

-Slowly contraction-Slowly contraction-High O-High O22 usage usage -Rich blood supply and myoglobin-Rich blood supply and myoglobin-Hence red fibers-Hence red fibers-Less fatigue and high endurance-Less fatigue and high endurance-Rich mitochondria-Rich mitochondria-Little glycogen-Little glycogen-Less contractile force-Less contractile force-E.g. postural muscles-E.g. postural muscles

Intermediate fibresIntermediate fibres Fast contractionFast contraction Aerobic metabolism Aerobic metabolism Moderate blood, myoglobin and Moderate blood, myoglobin and

mitochondria,mitochondria, Moderate glycogenModerate glycogen Moderately fatigue resistanceModerately fatigue resistance Intermediate powerIntermediate power E.g walking, sprintingE.g walking, sprinting

Fast twitch (white) fibresFast twitch (white) fibres

-contract fast-contract fast-anaerobic metabolism-anaerobic metabolism-little myoglobin, blood,-little myoglobin, blood,-mitochondria, increased-mitochondria, increased-glycogen--white fibers fatigable-glycogen--white fibers fatigable-powerful, short-term--ball hitting-powerful, short-term--ball hitting

White and red muscle fibres

Nerve and blood supplyNerve and blood supplyMuscle tissue is richly innervated by nervesMuscle tissue is richly innervated by nervesEach myofibre is innervated by one nerve fibreEach myofibre is innervated by one nerve fibreOr one nerves fibre innervates several myofibresOr one nerves fibre innervates several myofibres

Motor innervationMotor innervation: At the neuromuscular junction: At the neuromuscular junction found at the sarcolemma. Acetylcholine is the found at the sarcolemma. Acetylcholine is the

neurotransmitterneurotransmitter

Sensory innervationSensory innervationAt the specialized At the specialized muscle spindles muscle spindles inside the muscle near inside the muscle near

myotendinous junctionsmyotendinous junctionsThey are proprioceptive fibres for They are proprioceptive fibres for strechstrech

Muscle is also richly supplied with blood. Small arteioes run Muscle is also richly supplied with blood. Small arteioes run within the muscle fascicleswithin the muscle fascicles

Neuromuscular Junction

Nerve ending

Muscle cell

Muscle regenerationMuscle regeneration

Muscle fibres have limited ability to Muscle fibres have limited ability to regenerateregenerate

after injuryafter injury

Fibrous tissue multiply to replece injured Fibrous tissue multiply to replece injured muscle cellsmuscle cells

SatelliteSatellite cells can also differentiate to cells can also differentiate to replace dead cellreplace dead cell

Muscle massMuscle mass HypertrophyHypertrophy -Increase in muscle fibre cell size with exercise-Increase in muscle fibre cell size with exercise

AtrophyAtrophy -Decrease in muscle fibre size e.g. -Decrease in muscle fibre size e.g.

HyperplasiaHyperplasia - Increase in number of muscle cells- Increase in number of muscle cells

Smooth muscle cells

Cardiac muscle cells

Optics of light microscopy