1. Skeletal Muscle – Common Features Most have the following features: Nervous control – we can control muscle action Contractility – muscles can contract Extensibility – muscles can stretch under force

2. Skeletal Muscle – Common Features Elasticity – can return to their original size Atrophy – will decrease in size (waste away) when not used Hypertrophy – will increase in size (grow) in response to exercise

3. Muscle Fibre Arrangement Organised in different ways depending on shape and function Three main types: FusiformPennateRadiate

4. Fusiform Muscles Run the length of the muscle body Are designed for mobility Generate a low amount of force Example: –Biceps brachii

5. Pennate Muscles Fibres in pennate muscles run at angles to the tendons Not as mobile as fusiform muscles Can generate much more force though

6. 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

8. Structure of Skeletal Muscle Starting right in the middle of a muscle: Each muscle contains thousands of muscle fibres Fibres run the length of the muscle Each fibre is covered in Endomysium, which helps the fibres bind into bundles

9. Structure of Skeletal Muscle These bundles of fibres are called Fasciculi Fasciculi then also bind together in bigger bundles, surrounded by a connective tissue called Perimysium

10. 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.

11. This is one muscle fibre, surrounded by Endomysium A bundle of fibres together is a Fasciculi, surrounded by Perimysium