Human Body Study Guide Locomotion, necessary to escape danger, obtain food and shelter, and reproduce, is accomplished by the interaction of the skeletal and muscular systems, and coordinated by the nervous system. Functions of the Skeletal System: The digestive system consists of organs that are responsible for the mechanical and chemical breakdown of food. The breakdown process results in molecules that can be absorbed and transported to cells. mechanical digestion: The physical breakdown of 1. provides shape & structure food into smaller pieces. 2. enables you to move 3. produces blood cells mouth: teeth break food into pieces esophagus: forms food into a ball stomach: churns food into a liquid 4. protects organs chemical digestion: The use of acids and enzymes to change the food into nutrient molecules. 5. stores minerals and other materials mouth: adds saliva to begin digestion stomach: adds acid and enzymes (pepsin) small intestine: adds bile and pancreatic enzymes large intestine: bacteria work on indigestible material The circulatory system moves substances to and from cells, where they are needed or produced, responding to changing demands. Absorption is the process by which nutrient molecules are taken into (absorbed) into the blood stream to be delivered to the cells of the body. The circulatory works with many systems: digestive: blood collect digested nutrients and delivers them to body cells respiratory: the blood collects and delivers needed oxygen and carries waste to be removed by the lungs Arteries carry blood away from the heart. Veins carry blood toward the heart. Capillaries allow for the exchange of needed materials between the blood and body cells. Diffusion occurs in the capillaries. It is when molecules travel from an area if high concentration to an area of lower concentration. This is how the exchange of oxygen and nutrients happen. During respiration, cells use oxygen to release the energy stored in food. The respiratory system supplies oxygen and removes carbon dioxide (gas exchange).