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