The skeletal system consists of a number of different types of tissue. The most obvious ones are the bones themselves, the dense and rigid structures that support the body and the connective tissues that connect those structures. The less obvious ones are the ones within the bones themselves including the marrow in which the body produces red blood cells and other important substances vital to the body's function.
Within the marrow there are actually two types, red and yellow. At birth the marrow consists entirely of red marrow and as the body ages some of it is converted to yellow. Red and most white blood cells as well as platelets are produced in the red marrow. One of the other functions of marrow is producing stem cells of various types.
Cartilage is another tissue found in the skeletal system and a particularly specialized one. Cartilage is critical in supporting and cushioning various parts of the skeletal system and is interesting in that it cannot heal itself in the ways that other tissues in the system can.