A muscle is made up of bundles of muscle tissue. This muscle tissue consists of muscle cells, each having a lot of mitochondria.
Mitochondria produce energy through cellular respiration, which enables muscles to contract and move. The high concentration of mitochondria in muscle cells provides the energy required for movement.
Muscles cover the skeleton and are attached to bones by strong tendons. It’s important to remember that muscles work by contracting. When they contract, muscles shorten, pulling on the bone they’re attached to, and this moves the bone.
Muscles work in pairs at joints to enable movement; these are known as antagonistic pairs. One muscle in the pair contracts while the other relaxes. For example, at the elbow joint:
Muscles can only pull, not push. When a muscle contracts, it pulls the bone to which it is attached.