STEVE GSCHMEISSNER / SCIENCE PHOTO LIBRARY STEVE GSCHMEISSNER / SCIENCE PHOTO LIBRARY
Skeletal muscle. Coloured scanning electron micrograph (SEM) of skeletal (striated) muscle fibres. Each muscle fibre (green bundle) consists of a number of smaller vertical strands called myofibrils enclosed by supportive connective tissue (blue). The myofibrils are crossed by transverse tubules and each myofibril is made up of many contractile units called sarcomeres. Sarcomeres contain protein filaments of myosin and actin which can slide over one another, allowing the muscle to contract. Skeletal muscle is under the conscious control of the brain. Magnification unknown.
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