Quick Facts
The epimysium is the fibrous sheath about an entire muscle (Dorland, 2011).
Related parts of the anatomy
Structure
The epimysium is a well-defined layer of dense irregular connective tissue, which completely envelopes the muscle belly. It consists primarily of type I collagen fibers, which are tightly arranged to form a relatively strong fibrous covering of the muscle (Standring, 2016).
Blood vessels travel through this collagenous sheath around the outside of the whole skeletal muscle, providing the skeletal muscle with blood supply.
Nerves travel through the epimysium around the outside of the whole skeletal muscle, innervating the skeletal muscle.
Key Features/Anatomical Relations
The epimysium surrounds, or envelops the muscle, separating it from the surrounding organs and tissues. The three collagenous sheaths, the epimysium, perimysium, and endomysium, unite and fuse where the muscles connect to adjoining structures such as tendons (Standring, 2016).
Function
The epimysium separates the muscle from adjacent structures and carries blood vessels and nerves which supply the muscle tissue. The contraction of muscle requires a vast amount of energy; therefore, an extensive vascular network is necessary in order to deliver this energy to the muscle tissue, and in addition to carry away the by-products (i.e., metabolic waste) of the muscle contraction. The epimysial nerves will innervate the skeletal muscle fascicles and the muscle fibers within them, carrying the signal required to initiate contraction of the muscle tissue (MacIntosh, Gardiner and McComas, 2006).
As the epimysium is composed of collagen and elastin fibers, it contributes to the resistance of a muscle to tensile forces.
List of Clinical Correlates
—Vasculitis
—Mysium damage
—Connective tissue disease
References
Dorland, W. (2011) Dorland's Illustrated Medical Dictionary. 32nd edn. Philadelphia, USA: Elsevier Saunders.
MacIntosh, B. R., Gardiner, P. F. and McComas, A. J. (2006) Skeletal Muscle: Form and Function. Human Kinetics.
Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41 edn.: Elsevier Limited.
