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.
Another leafy vegetable high in beta carotene in the form of vitamin A, kale has 478 milligrams of the nutrient and 20 calories per half cup serving. Kale recipes to try: â¢ Kale Chips. â¢ Roast Cod with Bacon, Potatoes, and Kale. â¢ Kale Salad with Glazed Onions and Cheddar.
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.wo of the most common sources are retinol and beta-carotene. Retinol is sometimes called âtrueâ vitamin A because it is nearly ready for the body to use. Retinol is found in such animal foods as liver, eggs, and fatty fish.