MANFRED KAGE / SCIENCE PHOTO LIBRARY MANFRED KAGE / SCIENCE PHOTO LIBRARY
Skeletal muscle. Light micrograph of a longitudinal section through skeletal muscle fibres. Muscle fibres are extremely long, cylindrical cells (running from top to bottom). Running the length of each fibre are thin threads called myofibrils (not seen). The cross striations (pink stripes) are due to the regular arrangement of contractile proteins in these myofibrils. These proteins (actin and myosin) slide past each other when a muscle contraction takes place, shortening the fibre. The oval structure at lower centre is most likely a small blood vessel. Skeletal muscle is muscle under voluntary control. Magnification unknown.
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