Gills remove dissolved oxygen from the water as it passes over them - dissolved oxygen diffuses into the blood. Gills also give off carbon dioxide. Gills are the exchange point. Insects a. Spiracles - tiny openings in the exoskeleton of insects through which air enters the insects body. Lungs take in oxygen and remove carbon dioxide from the blood.
Capillaries is where exchange occurs.
Human Respiration - diagram of respiratory system A. Diaphragm 1. Defn - sheet of muscles across the bottom of the chest which pump air into and out of the lungs. This increases the volume of the chest cavity. Lower pressure in the lungs allows air to rush in through the nose and mouth. B. Nose and mouth both allow air to enter the body.