Quick Facts
The belly of a muscle is the fleshy contractile part of a muscle (Dorland, 2011).
Related parts of the anatomy
Structure
The “belly” of the muscle is typically the largest or thickest portion of the muscle. The muscle belly is composed of the fascicles, which are groups of muscle fibers bundled together. The muscle belly is encased in a connective tissue sheath called the epimysium.
Key Features/Anatomical Relations
The muscle belly lies between the origin and insertion points of the muscle. In muscles which have multiple origins, for example the two-headed biceps femoris or biceps brachii muscles, the fibers from the multiple heads converge to form one muscle belly prior to the insertion point (MacIntosh et al., 2006).
Function
The muscle belly is the collection of the muscle fibers contained within their connective tissue sheaths. The muscle fibers, or myocytes, contain myofibrils that contain the contractile units of the muscle called sarcomeres. The sarcomeres are responsible for the ability of the muscle to contract and relax.
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.
