1 Each muscle fibre ( muscle cell ) is covered by a plasma membrane sheath which is called the sarcolemma. 2  Tunnel-like extensions from the sarcolemma pass through the muscle fibre from one side of it to the other in transverse sections through the diameter of the fibre.keletal muscles consist of 100,000s of muscle cells (also known as muscle fibers) that perform the functions of the specific muscle of which they are a part.
Green vegetables are also a major source of iron and calciumfor any diet. Swiss chard and spinach are not considered good sources of calcium, due to their high content of oxalic acid. Green leafy vegetables are rich in beta-carotene, which can also be converted into vitamin A, and also improve immune function. Millions of children around the world have an increased risk of blindness, and other illnesses because of inadequate dietary vitamin A from green leafy vegetables.
Some carotenoids, such as lycopene, zeaxanthin, lutein, capsanthin, and canthaxanthin are not converted into vitamin A in the body. But again, they are powerful cancer fighters, prevalent in fruits and vegetables.There is abundant evidence that lycopene in particular helps reduce the risk for prostate cancer.range and yellow fruits and vegetables have high vitamin A activity because of the carotenoids they contain. Generally, the deeper the color of the fruit or vegetable is an indication of a higher concentration of carotenoids. Carrots, for example, are especially good sources of beta-carotene.