H zone
anatomy
Quick Summary
ultrastructure of a group of myofibrils
Figure 7: Ultrastructure of a group of myofibrils, showing the sarcoplasmic reticulum and transverse tubules, which constitute the two membrane systems within a muscle fibre.
The H zone is a region within the A band of a sarcomere, the basic contractile unit of muscle. It appears lighter than the overlap region of the A band and contains only thick filaments, without any thin filaments. This zone is part of the structure responsible for muscle contraction, where filaments slide past each other rather than shortening. The primary function of filaments like myosin is to produce force and movement, essential for muscle contraction.123
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