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.
Beta-carotene is a precursor for vitamin A. The body needs to convert it to retinol or vitamin A for use. Beta-carotene is found naturally in mostly orange and dark green plant foods, such as carrots, sweet potatoes, mangos, and kale.itamin A is a family of fat-soluble compounds that play an important role in vision, bone growth, reproduction, cell division, and cell differentiation. Vitamin A is important for healthy bones.