Physiology of the Respiratory System

Objectives You will be able to… 1.Explain how air enters and leaves our lungs. Note: This covers all of the information in this presentation.

Pulmonary Ventilation Ventilation: the movement of air into and out of the lungs, a.k.a. breathing. Two phases of ventilation: – Inhalation Drawing air into the lungs. – Exhalation Expulsion of air from the lungs.

Inhalation How does air get into your lungs? – Respiratory muscles contract to enlarge the thorasic cavity. – Respiratory muscles include: Intercostal muscles – Located between the ribs. Diaphragm – Located below the rib cage between the thorasic and abdominal cavities.

Inhalation Diaphragm – When it contracts it flattens out and moves downward. What will happen to the thorasic cavity? – This increases the vertical space (volume) of the thorasic cavity.

Inhalation Intercostal Muscles – When they contract the rib cage moves out and up. – This also increases the amount of space (volume) in the thorasic cavity.

Inhalation How does this change in volume allow us to breath? – There is pressure exerted on the thorasic cavity and lungs (greater than atmospheric pressure). – Pressure x Volume = constant PV = k (Boyles Law) – P = k/V If the volume of the thorasic cavity increases, the pressure will do what? – Decrease!!! – When the pressure exerted on the lungs decreases below atmospheric pressure, air is pushed into the lungs.

Exhalation When the respiratory muscles relax, the thorasic cavity returns to its normal dimensions. – The rib cage moves back down and in. – The diaphragm thickens and moves upward. When the volume decreases, what happens to the thorasic cavity pressure? – Increases! When the pressure is higher than the atmospheric pressure, air is no longer pushed into the lungs.

Inhalation and Exhalation