Oct 2015 03

The structure of muscle

By: Dave Wheeler

I've blogged before about how muscles work:

But today it's time to look at the detail of the make up of muscle fibres.

 

pic by stockimages @ freedigitalphotos.net

 

The structure of muscle

Muscles are made of muscle fibres.

Muscle fibres are bundled together. These bundles are called Fasciculi.

There can be anything from 10 to 100 muscle fibres per Fascicle:

  • Big powerful muscles, like the Quads will have a lot of fibres to each Fascicle.
  • Small precision muscles, like those in your fingers will have only a few fibres to each Fascicle.

Each muscle fibre is surrounded by a layer called Endomysium which you can think of as grease to allow the fibres to move against eachother without friction.

Each Fascicle, or bundle or fibres, is also surrounded by a layer of "grease", called Perimysium, this time to allow the bundles to run smoothly against other bundles.

All of the bundles which form the entire muscle are then surrounded by a final layer of "grease" called the Epimysium which protects the muscle from rubbing against  nearby muscles and bones.

Individual muscle fibres are roughly the thickness of a human hair (well, actually very slightly thinner - anything from 10 to 80 microns, which is 0.01mm-0.08mm).

Each individual muscle fibre is then divided along its length into chunks of cylindrical structures called Myofibrils.

Each muscle fibre can contain 100's or 1000's of Myofibrils, depending on the fibre's length.

Myofibrils are basically bundles of Actin and Myosin proteins which run the length of the fibre.

Finally, each Myofibril is broken down into repeating segments called Sarcomeres.

It's these Sarcomeres that peform the main funtion of muscle, which is contraction.