Sarcolemma

Sarcolemma is the name of the cell membrane that encloses each muscle cell, specifically muscle cells ("muscle cell" = "muscle fibre" = "muscle fiber").

Structure of Sarcolemma

Each sarcolemma has a similar biochemical composition to that of a plasmalemma, which is another word for a (general) cell membrane. The structure of muscle cells specifically is such that tunnel-like extensions from the sarcolemma pass across muscle cells (="muscle fibres" etc.) from side to side, so they are said to be transverse. These extensions of the sarcolemma are called transverse tubules, which is often abbreviated to simply "T tubules".

Functions of Sarcolemma

Sarcolemma perform an important role in the muscle contraction process - see also types of muscle contractions. When the Muscle Action Potential (which is a form of electrical "instruction") travels along the sarcolemma of muscle fibres, then into the transverse tubules, calcium ions (Ca²⁺) are released into the sarcoplasm.

The word sarcolemma is formed from two parts:

• sarco- which means "flesh", and
• -lemma which means "sheath"

Sarcolemma is one of the layers of muscle tissue. Overall, the main layers of muscle tissue include:

• Sarcolemma is the cell membrane that encloses each muscle cell (which is also known as a muscle fibre).
• Endomysium is connective tissue that wraps each individual muscle fibre.
• Perimysium is connective tissue that wraps bundles of muscle fibres - the "bundles" being known as fasicles.
• Epimysium is connective tissue that wraps the whole muscle.
• Fascia (or "deep fascia") is a layer of thickened connective tissue that covers the entire muscle and is located over the epimysium.

Compare sarcolemma, which covers muscle cells, with tendon sheaths, which cover tendons.