tc. Irregular bones are varied in shape and size and "tend to be more specialised in their location" (Sheridan, 2002). The vertebrae and some of the bones in the skull are irregular bones. Sesamoid bones act as pulleys to guide tendons during movement and are usually a small mass of bone that forms where there is pressure and extra strength needed e.g. the patella or kneecap.
             As well as bone in the skeletal system we also have tendons (which connect muscles to bone), ligaments (which connect bone to bone), and cartilage. Cartilage "both resembles and differs from bone" (Marieb, Benjamin, 2002). Cartilage is much more flexible than bone and provides two major functions within the skeletal system. The two main types of cartilage are hyaline cartilage and fibro-cartilage. Hyaline cartilage is glass like in appearance and is usually found coating the ends of bone providing a smooth gliding movement at the joints. Fibro-cartilage contains collagen, which makes it very strong and gives added support to the bone e.g. the vertebral discs to the vertebral column.
             Almost every bone in the body joins to another bone forming a joint. Joints hold bones together making them secure but also allowing for movement. There are three types of joint in the body – fibrous, cartilaginous and synovial. Fibrous joints provide no movement as the bones are tightly bound together with fibrous connective tissue e.g. the joints between the bones of the skull. Cartilaginous joints provide a slight movement where the bones are connected at the joint by fibro-cartilage e.g. the pubis, joints within the vertebral column. Synovial joints (see diagram 3) allow for free movement as a fibrous capsule, which encloses the joint, holds the bones together. This capsule is lined with synovial membrane, which secretes synovial fluid into the space between the two bones called the joint cavity. The synovial fluid acts as a lubricant to the ends of the...