noun, plural: sarcomeres
A segment consisting of a highly organized assembly of filaments delimited by two Z lines; the contractile unit of a myofibril
The sarcomere is regarded as the contractile unit of a myofibril since it contains the smallest functional structures and molecules essential for muscle contraction. Two important proteins namely actin and myosin form thin and thick filaments, respectively. These filaments are arranged in a way that they are partly overlapping and may slide past each other during contraction.
Word origin: Greek sarco (flesh) + –mere, from meros (part)