1. Gas Exchange By: Jose Posada & Andrés González

2. Distinguish between ventilation, gas exchange and cell respiration Ventilation : Is the process of inhaling and exhaling, with oxygen entering the alveoli (large surface area). Cell Respiration : The chemical process occurring in the mitochondria where energy is released as ATP. Gas exchange : Process of exchanging one gas for the other between the alveoli and capillaries. (Carbon dioxide for oxygen).

4. Explain the need for a ventilation system A ventilation system is needed in order to obtain oxygen for living organisms and to get rid of carbon dioxide. Surface diffusion utilized by many smaller organisms is not sufficient in supplying the oxygen needs of the body. It is also needed to maintain a concentration gradient in the alveoli.

5. Describe the features of alveoli that adapt them to gas exchange Cells secrete fluid making the inner surface moist. Single layer of cells allowing for short diffusion distance. Increase in surface area. Dense network of capillaries near the surface.

6. Diagram

7. Mechanism of ventilation of the lungs When we inhale The diaphragm moves down and becomes flat because abdominal muscles relax(allowing for more air). The volume of the thorax increases, air flows into the lungs. External intercostal muscles contract. When we exhale