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.
Liver, whole or fortified milk and milk products contain vitamin A. Leafy green vegetables such as spinach, broccoli and brussels sprouts as well as yellow and orange fruits and vegetables such as cantaloupe, carrots, sweet potatoes and squash contain beta-carotene, which converts to vitamin A in the body.ood sources include fortified milk and margarine, cereals, beef, egg yolks, liver and fatty fish such as salmon and sardines. You can also fight a vitamin D deficiency by getting moderate sun exposure -- the exact amount of sun you need depends on the time of year and your location.