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.
This chart will help you find foods that are a good source of vitamin A. Both animal and plant foods have vitamin A activity. Retinol, also called preformed vitamin A, is the natural form found in animals.Carotenoids, found in plants, are compounds that the body can convert to vitamin A.Liver is the single best food source of vitamin A. However, many experts recommend eating liver only once or twice a month because of the toxic substances it can contain. Environmental pollutants tend to congregate in an animal's liver.oth animal and plant foods have vitamin A activity. Retinol, also called preformed vitamin A, is the natural form found in animals. Carotenoids, found in plants, are compounds that the body can convert to vitamin A.