1. Digestive
    1. Mouth
    2. Sophagus
    3. Stomach
    4. Intestines
  2. Circulatory
    1. Heart
    2. Veins
    3. Arteries
    4. Capillaries
  3. Respiratory
    1. Nose
    2. Lungs
    3. Trachea
  4. Nervous
    1. Brain
    2. Spinal Cord
    3. Nerves