FRANCIS LEROY, BIOCOSMOS / SCIENCE PHOTO LIBRARY FRANCIS LEROY, BIOCOSMOS / SCIENCE PHOTO LIBRARY
Muscle cell anatomy. Artwork of the anatomy of a muscle cell, also known as a muscle fibre. The cell is surrounded by a plasma membrane called the sarcolemma (grey). Within the cell are myofibrils, bundles of actin (blue) and myosin (white) fibres surrounded by a sarcoplasmic reticulum (yellow). The sarcoplasmic reticulum holds a reserve of calcium ions, which are needed for contraction. Mitochondria (white with red outline) within the myofibrils provide the energy needed for contraction.
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