Perimysium

Perimysium is the name given to the fibrous sheath that surrounds (covers) each bundle of single muscle fibres, the bundle being known as a fascicle.

Some texts describe perimysium as "dividing" or "grouping" individual muscle fibres into bundles or fasciculi.

Structure of Perimysium

Perimysium contains mainly collagen, but also intra-muscular fat (marbling), blood vessels and nerves that maintain blood flow and innervate the fascicles. Each fascicle receives branches of these blood vessels and nerves.

Location of Perimysium

Perimysium should not be confused with other layers of connective tissue located in the structure of muscles, such as endomysium or epimysium - see below.

Overall, the layers of muscle tissue are located as follows:

• 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 layer of epimysium.