Final answer:
A sarcomere is the basic unit of muscle contraction in skeletal muscle, defined as the space between two consecutive Z lines or Z discs. It contains the A band, I band, H zone, and M line.
Step-by-step explanation:
A sarcomere is the basic unit of muscle contraction in skeletal muscle. It is defined as the space between two consecutive Z lines or Z discs, which mark the border of a sarcomere. The sarcomere contains several important structures, including the A band, I band, H zone, and M line.
The A band is the central region of the sarcomere and consists of overlapping thin (actin) and thick (myosin) filaments. The I band is a relatively clear region on either side of the A band, composed mainly of thin filaments. The H zone is the region in the center of the A band where thick filaments do not overlap with thin filaments. The M line is located at the center of the H zone.