Bodily movement is carried out by the interaction of the muscular and skeletal systems. For this reason, they are often grouped together as the musculo-skeletal system. Muscles are connected to bones by tendons . Bones are connected to each other by ligaments . Where this connection occurs is typically called a joint .
Muscles cause movement by contracting and relaxing.
An example would be the contraction of the biceps and a relaxation of the triceps. This produces a bend at the elbow. The contraction of the triceps and relaxation of the biceps produces the effect of straightening the arm. This same interaction between the muscular and the skeletal system is also what makes breathing possible. Blood cells are produced by the marrow located in some bones.