Skeleton and Joints

Choice B is an immovable joint, while choices C and D are freely moveable synovial (diarthrotic) joints.

Synovial joints have synovial fluid between the articulating bones. Fibrous joints have fibre between the articulating bones. Cartilaginous joints have cartilage between the bones. Amphiarthroses are “slightly moveable” joints.

A “long bone” has a length that is significantly longer than its width. A carpal (a bone of the wrist) is a short bone.

Wrist bones are carpals; hand bones are metacarpals (ankle bones are tarsals).

Phalanges (singular phalanx) are the bones of the fingers or toes. Metacarpals are the bones of the hand.

The lubricant action ensures a friction-free movement, while the relative incompressibility of the fluid allows, for example, the body weight to be distributed over the surface area of the knee joint (think about Pascal’s principle). Choice B is true but is a biological function.

The membrane around bones houses the bone-forming cells (osteoblasts) and the bone-resorbing cells (osteoclasts).

The occipital bone forms the base of the cranium.

The acetabulum is the “socket” into which fits the ball of the femur.

The occipital bone forms the floor of the cranium.