In your body, you have only two types of bone tissue: cortical and cancellous bone. In this lesson, we will learn about the structure and function of cancellous bone, which plays a crucial role in producing blood cells and stem cells and is the primary tissue affected by osteoporosis.
balaclava (plural balaclavas) 1  A warm cap shielding the neck and head, often made out of wool. ( 2 chiefly Canada) A ski mask with holes for the eyes and, sometimes, the nose and mouth, which may be rolled up and worn like a toque or pulled over the face for greater protection.
If cold air bothers you during exercise, you can wear a scarf or facemask to help âprewarmâ the air. I use a balaclava to keep my face warmer in very cold conditions and avoid frostbite on my cheeks. There are many designs that have extra materials over the mouth and nose to prewarm the air.