Muscles and bones work together in tandem meaning that the muscles attach to tendons and ligaments and the tendons and ligaments attach to bones. The muscles pull the bones, causing movement. The movements that the muscles make are ultimately controlled by the brain and nervous system.
The human skeleton is comprised of 206 bones. Bones begin to form prior to birth. Initially the skeleton is fluid cartilage; soon after the bones begin to ossify, meaning they take on calcium phosphate, causing them to harden. At age 20, the human bones are considered to be fully developed. There are 600 muscles in the human body.