Muscular Tissue

Muscular tissue is made of elongated cells called muscle fibres. Each fibre is enclosed by a cell membrane called the sarcolemma, and its cytoplasm is called the sarcoplasm. Within the sarcoplasm lie large numbers of fine, contractile fibrils called myofibrils, themselves built from the two contractile proteins actin and myosin. Depending on the type of muscle, a muscle cell may contain one nucleus or several.

When stimulated, a muscle fibre contracts and shortens in length — this is why muscular tissue is described as a contractile tissue. It is a vascular tissue (well supplied with blood vessels) and is also innervated (supplied by nerves), and its cells contain unusually large numbers of mitochondria to meet the high energy demand of repeated contraction. …