Gas ExchangeBy: Jose Posada & Andrés González

Distinguish between ventilation, gas exchange and

cell respirationVentilation: 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).

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.

Describe the features of alveoli that adapt them to gas

exchangeCells 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.

Diagram

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

Abdominal muscles contract and the diaphragm becomes dome-shaped, moving up. The volume of the thorax decreases and intercostal muscles contract causing pressure to increase. Air flows out to equalize pressure gradient.