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.
You can also contribute to your vitamin A intake by including good sources of beta-carotene in your diet, as this can be converted into vitamin A by the body. The main food sources of beta-carotene are: 1  yellow, red and green (leafy) vegetables, such as spinach, carrots, sweet potatoes and red peppers.itamin A. Vitamin A is also known as retinol and has several important functions. These include: 1  helping your immune system to work as it should against infections. 2  helping vision in dim light. 3  keeping skin and the linings of some parts of the body, such as the nose, healthy.