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.
cap - a tight-fitting headdress. 1  balaclava, balaclava helmet - a cap that is close-fitting and woolen and covers all of the head but the face. 2  Balmoral, bluebonnet - a brimless dark blue Scottish cap with a flat top and a plume on one side. 3  baseball cap, golf cap, jockey cap - a cap with a bill.