Lecture 5

Muscle tissue, Structure of skeletal muscle, Classification

Muscle Tissue: Composed of contractile unites possessing the properties of

ExcitabilityContractilityExtensibilityElasticity

Functional Unit:

Muscle fiber

Smooth muscle fiber VisceralStriated muscle Skeletal / Cardiac

Skeletal Muscle

Functions: Provides force for Movement and PostureStabilizes JointsGenerates heat

AttachmentsOrigin /Insertion

Direct/Indirect (Tendon/Aponeurosis)Transmits forces (Fiber orientation?)

BellyGenerates force

StructureFiber covered by Endomysium—SarcolemmaFascicle covered by PerimysiumMuscle covered by Epimysium Epitenon

Muscle force is a function of

Number of muscle fibersPennation Angle

Pennation Angle

Unipennate MusclesBipennate MusclesMultipennate Muscles

Multipennate Bipennate

Accessory StructuresFasciaBursaTendon Sheath

Extensive Blood Supply

Extensive Innervations:Motor UnitSpindles/Golgi tendons endings/free nerve endings/Paciniancorpuscles

Regeneration of muscle tissue is possible

Spindle-shaped (fusiform)

Sheet like (planus)

CLASSIFICATION

Shapes

CLASSIFICATION

Functional: Prime Movers / AgonistsSynergistAntagonists

Specific Action:Flexor/ExtensorAdductor/AbductorSupinator/PronatorSphincter/DilatorLevator/DepresssorRotator

Number of joints crossed: UniarticularBiarticularPolyarticular

Developmental Origin and Innervation:

Somatic muscles – somatic motor innervationVisceral muscles – visceral autonomic motor innervation

Composition:

White fibers: More myofibrils more forceLess myoglobin short duration

Red Fibers: Less myofibrils weak force More myoglobin long duration

NAMING CONVENTIONS

ActionShapeRegional LocationDirection of fibersNumber of headsNumber of belliesAttachment sitesRelative position