STEVE GSCHMEISSNER / SCIENCE PHOTO LIBRARY STEVE GSCHMEISSNER / SCIENCE PHOTO LIBRARY
Cardiac muscle. Coloured transmission electron micrograph (SEM) of cardiac muscle fibrils (pink) from a healthy heart. Mitochondria (brown blobs) supply the cells with energy. At lower centre is an intercalated disc (purple). This is a double membrane that separates adjacent cells in the muscle fibres. Intercalated discs facilitate the synchronised contraction of the muscle. Cardiac muscle is under subconscious control and continuously contracts to pump blood around the body without tiring.
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