Stefan SivkovStefan Sivkov

MU - PlovdivMU - Plovdiv

Why do we study muscles?Why do we study muscles?

Body movementBody movement

Skeletal movementSkeletal movement

Movement of bloodMovement of blood

Movement of foodMovement of food

Uterine contractionsUterine contractions

Muscle disordersMuscle disorders Food resourceFood resource Weight controlWeight control

– Use it or looseUse it or loose itit

General characteristicsGeneral characteristics

6600 00 musclesmuscles - 40 % - 40 % body weightbody weight Organ structureOrgan structure

musclemuscle, , connectiveconnective, , nervenerve, , epithelialepithelial tissuetissue

FunctionsFunctions

• movementmovement

• heat productionheat production

• posture controlposture control

• supportsupport

EmbryogenesisEmbryogenesis

Mesodermal originMesodermal origin

SomitesSomites – – primary mesodermal segmentsprimary mesodermal segments

sclerotomessclerotomes – – vertebral columnvertebral column

myotomesmyotomes – – muscles of body and limbsmuscles of body and limbs

dorsaldorsal – – back musclesback muscles

ventralventral – – antero-lateral and limb antero-lateral and limb

musclesmuscles

Branchial gillsBranchial gills – – facial and neck musclesfacial and neck muscles

Topological organization of Topological organization of musclesmuscles

Paired and symmetricalPaired and symmetrical

Segmental – in the bodySegmental – in the body

Shortest distance between origin and insertionShortest distance between origin and insertion

Perpendicular to the joint axesPerpendicular to the joint axes

ClassificationClassification

According to the formAccording to the form According to the fiber directionAccording to the fiber direction According to the functionAccording to the function According the number of jointsAccording the number of joints According to the positionAccording to the position

Structure of the muscleStructure of the muscle

Contractile (fleshy) partContractile (fleshy) part

ExtrafusalExtrafusal muscle fibersmuscle fibers Muscle fibersMuscle fibers

Muscle bundlesMuscle bundles

MuscleMuscle

Connective tissue Connective tissue in the musclein the muscle

1.1. EndomysiumEndomysium. Thin layer around . Thin layer around

the muscle fiber.the muscle fiber.

2. Perimysium.2. Perimysium. Thicker layer around Thicker layer around

a bundle of muscle fibers (a bundle of muscle fibers (fasciclefascicle). ).

3. Epimysium.3. Epimysium. The outer connective The outer connective

tissue layer.tissue layer.

Muscle spindleMuscle spindle

ProprioreceptionProprioreception

IntrafusalIntrafusal muscle fibers muscle fibers thinthin (30 (30 m mm) m) andand shortshort (m (mmm)) central portioncentral portion ( (nuclear bagnuclear bag) )

- - sensory endingssensory endings peripheral partsperipheral parts

- motor endings of motor endings of -motoneurons-motoneurons

Intrafusal fibersIntrafusal fibers – – nuclear bagnuclear bag andand nuclear nuclear

chainchain.. Fusimotor fibersFusimotor fibers – – motor nerve fibersmotor nerve fibers. . PrimaryPrimary (Іа) (Іа) andand secondarysecondary (ІІ) (ІІ) sensory nerve sensory nerve

fibersfibers..

Registers changes in the muscle length and Registers changes in the muscle length and

speed. Sensation is modulated from CNS by speed. Sensation is modulated from CNS by

fusimotor systemfusimotor system::

- - static gamma system static gamma system for changes in lengthfor changes in length

- - dynamic gamma systemdynamic gamma system for changes in for changes in

speedspeed..

Muscle tendonMuscle tendon

Attachment of muscleAttachment of muscle

formform – – according to the muscle formaccording to the muscle form

thicknessthickness – – up toup to 20% 20% muscle thicknessmuscle thickness

structurestructure

– collagen fiberscollagen fibers

– peritendineumperitendineum – – between and around the fibersbetween and around the fibers

– Golgi corpusclesGolgi corpuscles – – stretch receptors stretch receptors

– blood vesselsblood vessels – – less than in the muscleless than in the muscle

TypeType I I muscle fibersmuscle fibers

Lowest contractile Lowest contractile velocityvelocity

Lowest cross section Lowest cross section surface surface

Highest aerobic capacityHighest aerobic capacity Lowest anaerobic Lowest anaerobic

capacitycapacity Slow, long-term Slow, long-term

contractioncontraction. . Long distance runners, Long distance runners,

swimmersswimmers

TypeType II II muscle fibersmuscle fibers

TypeType II-b II-b fibers havefibers have Highest contractile velocityHighest contractile velocity Highest cross section surface Highest cross section surface Lowest aerobic capacityLowest aerobic capacity Highest anaerobic capacityHighest anaerobic capacity Quick, short-term contractionQuick, short-term contraction. .

Sprint, weight-lifting, fitnessSprint, weight-lifting, fitness

TypeType II-a II-a fibersfibers are intermediateare intermediate. .

Auxiliary structuresAuxiliary structures

FasciaeFasciae

properproper – – one muscleone muscle

groupgroup – – synergic synergic

musclesmuscles

septaeseptae – – separate separate

neighbouring muscle neighbouring muscle

groupsgroups

Synovial vaginaeSynovial vaginae

Outer sheathOuter sheath

Inner sheathInner sheath

MesotenonMesotenon

Synovial bursaeSynovial bursae Beneath tendons and muscles, close to Beneath tendons and muscles, close to

their insertions their insertions

Sesamoid bonesSesamoid bones In tendons close to their insertionsIn tendons close to their insertions

Histological Histological characteristics of characteristics of

muscle fibersmuscle fibers

1.1. Cross striationCross striation. .

а. Dark and light bands. а. Dark and light bands.

1) А1) А--bandsbands. . DarkDark –– anisotropic anisotropic

2) І2) І--bandsbands. . LightLight - - isotropicisotropic..

б.б.1) Z disc1) Z disc in І band. in І band.

2) Н zone in 2) Н zone in А band; А band; М линия,М линия, dark in Н. dark in Н.

Muscle biomechanicsMuscle biomechanics

Internal biomechanicsInternal biomechanics Physiological transectionPhysiological transection – – perpendicular to fibersperpendicular to fibers Anatomical transectionAnatomical transection – – through the widest part of the musclethrough the widest part of the muscle Vector of muscle strengthVector of muscle strength

Effectiveness of muscle strength -Effectiveness of muscle strength - negatively proportional to the negatively proportional to the

angle between the vector and the boneangle between the vector and the bone

Muscle biomechanicsMuscle biomechanics

External biomechanicsExternal biomechanics

Movements in jointsMovements in joints. . Synergists and antagonistsSynergists and antagonists

Muscle strengthMuscle strength. . Number and length of the fibersNumber and length of the fibers

External biomechanicsExternal biomechanics

AttachmentsAttachments punctum mobilepunctum mobile - - insertioninsertion punctum fixumpunctum fixum - - originorigin

Levers of muscle contractionLevers of muscle contraction FulcrumFulcrum Point of loadPoint of load Point of strengthPoint of strength

I class leverI class lever – – of equilibriumof equilibrium II class leverII class lever

ІІА ІІА classclass – – of strengthof strength ІІВ ІІВ classclass – – of speedof speed

Theory of sliding myofilamentsTheory of sliding myofilaments

Cycle of crossed bridgesCycle of crossed bridges

ATP required. ATP required. Crossed bridgesCrossed bridges

MyosinMyosinOn both sides of the myofilamentsOn both sides of the myofilamentsBidirectional on one side of the myofilamentBidirectional on one side of the myofilament

А-bandsdo not changeА-bandsdo not change І-І-bandsbands narrownarrow