Skeletal Muscle Structure

Skeletal muscle structure consists of bundles of muscle fibres which are made up of smaller and smaller elements. Here we explain the structure of skeletal muscle and how musclular contraction works at a cellular level.


1. Epimysium

The epimysium is a protective covering which surrounds the muscle and holds it all together. It reduces friction between the muscle and surrounding bones and other tissues. The epimysium also extends at either end to form the tendons of the muscle.

2. Fasciculi

Fasciculi are bundles of muscle fibres. The fasciculi of larger muscles have more fibres per bundle and smaller muscles contain less. They range between 10 and 100 fibres per fasciculi. Another connective tissue called the perimisium surrounds groups of fasciculi.

3. Muscle Fibres

Individual muscle fibres are covered in yet another connective tissue known as endomysium. This acts to insulate each fibre. Muscle fibres again vary in size but can be up to 35cm long and 10 micrometers in diameter.

Each muscle fibre has a cell membrane called the Sarcolemma. Beneath this is the Sarcoplasm – a gelatinous fluid which fills most types of cells. Contained within the Sarcoplasm are mitochondria – the powerhouse of any cell, which produce it’s energy.

4. Myofibrils

Myofibrils are cylinder shaped structures found within each muscle fibre. Each muscle fiber contains hundreds or even thousands of them! Myofibrils actually consist of bundles of two proteins called Actin and Myosin which run the length of the muscle fiber and are vital for muscle contraction.

Another important feature for muscle contraction is the Sarcoplasmic Reticulum – a network of channels which surround the myofibrils. Muscle contracting is triggered and stopped by calcium which is stored within these channels.

Transverse tubules pass inwards from the Sacrolemma throughout the Myofibril, through which nerve impulses travel.

Each Myofibril can also be broken down into functional repeating segments along it’s length. These are called Sarcomeres. It is these segments the cause the muscle shortening seen during concentric contractions as the filaments slide over each other.

More on Sliding filament theory

Further reading:

Related articles

  • Magneium in sports nutrition

    Replenishing electrolytes after strenuous exercise is crucial, and magnesium has a particular role in muscular health and recovery. We look at the health benefits of…

  • Hamstring muscle contraction

    Sliding filament theory explains how muscles contract at a cellular level. Muscles contract in different ways depending on whether they are shortening, lengthening or staying…

  • DOMS - bounding exercise

    DOMS or delayed onset muscle soreness is a particular type of muscle soreness that sets in hours after exercise. It can range from mild discomfort…

  • Deep vein thrombosis DVT

    Deep Vein Thrombosis or DVT is a blood clot in a vein. It is most common in the calf muscle area, particularly following surgery and…

  • Tight calf muscles - benefits of stretching

    Tight calf muscles at the back of the lower leg is a common problem in athletes, especially those who run long distances. Here we explain…

Scroll to Top