Skeletal Muscle – Common Features

Most have the following features:Nervous control – we can control muscle actionContractility – muscles can contractExtensibility – muscles can stretch under force

Skeletal Muscle – Common Features

Elasticity – can return to their original sizeAtrophy – will decrease in size (waste away) when not usedHypertrophy – will increase in size (grow) in response to exercise

Muscle Fibre Arrangement

Organised in different ways depending on shape and functionThree main types:

FusiformPennateRadiate

Fusiform Muscles

Run the length of the muscle bodyAre designed for mobilityGenerate a low amount of forceExample:– Biceps brachii

Pennate Muscles

Fibres in pennate muscles run at angles to the tendonsNot as mobile as fusiform musclesCan generate much more force though

Pennate Muscles

Unipennate – fibres are found on only one side of a central tendon (ie: semimembranosus)Bipennate – fibres run off either side of a central tendon (rectus femoris)Multipennate – fibres branch out everywhere off several tendons (deltoid). This is the strongest type

Structure of Skeletal Muscle

Starting right in the middle of a muscle:

Each muscle contains thousands of muscle fibresFibres run the length of the muscleEach fibre is covered in Endomysium, which helps the fibres bind into bundles

Structure of Skeletal Muscle

These bundles of fibres are called FasciculiFasciculi then also bind together in bigger bundles, surrounded by a connective tissue called Perimysium

Structure of Skeletal Muscle

Finally, the outer layer of skeletal muscle is covered in another connective tissue called epimysium.Epimysium thickens towards the end of the muscle to form the tendon.

This is one muscle fibre, surrounded by Endomysium

A bundle of fibres together is a Fasciculi, surrounded by Perimysium