The Skeleton safeguards vital organs. The brain is encased in bones that are part of the skull. The thoracic cavity houses the heart and lungs, while the vertebral column supports and protects the spinal cord. The digestive system is located within the body, but can also be considered as internal because it is surrounded by fat and membranes-not bone! The kidneys filter the blood and release toxins through urine. The liver filters the blood of harmful substances produced by other organs of the body and stores them for removal later. The skeleton works in partnership with many other organ systems including the immune system, the endocrine system (which controls hormones), the cardiovascular system (which provides blood to all parts of the body), and the nervous system (which controls muscles). In conclusion, the skeleton is made up of a large number of different parts that work together to provide support for the body's various organs.