Key Questions for Understanding Respiratory Physiology

1. 4 Steps of Respiration 1.Pulmonary ventilation: also called breathing; air moves into and out of the lungs 2.External respiration: gas exchange between the alveoli and the pulmonary blood 3.Respiratory gas transport: oxygen and carbon dioxide must be transported to and from lungs and cells by the blood 4.Internal respiration: at systemic capillaries, gas exchange occurs between blood and tissue cells

2.Breathing depends on volume changes occurring in the thoracic cavity.

What are inspiratory muscles? When the diaphragm and the external intercostals contract, the size of the thoracic cavity increases. Since the lungs adhere tightly to the thorax walls, they are stretched to the larger size of the thorax

What causes the partial vacuum?  As the volume of the lungs increases, the gases in the lungs spread out, which decreases the pressure of the gas, producing a partial vacuum.

Why is expiration a passive process?  As the inspiratory muscles relax, the ribcage descends and the lungs recoil. This causes intrapulmonary gases to flow out to relieve pressure in the lungs. It requires no muscular effort.

What are the effects of the decrease in intrapulmonary volume?  The gases in the lungs are forced together, causing an increase in pressure. To equalize the pressure inside and outside the lungs, air flows out.

What is pneumothorax?  It is the presence of air in the interpleural space.  It is caused by a rupture of the visceral pleura, often the result of a chest wound.

What is normal tidal volume?  It is the volume of air moved by normal, quiet breathing.  It averages about 500 mL, or 1 pint

What is the inspiratory reserve volume?  IRV is the amount of air that can be taken forcibly over the tidal volume.  It is between 2100 and 3200 mL

What is the residual volume?  Residual volume is the amount of air that remains in the lungs and cannot be expelled. It normally equals 1200 mL.

What is vital capacity?  Vital capacity is the total amount of exchangeable air in the lungs. It normally equals 4800 mL  Tidal Volume (TV) + Inspiratory Reserve Volume (IRV) + Residual Volume (ERV) = Vital Capacity

Explain the difference between external and internal respiration.  External respiration is the actual exchange of gases between the alveoli and the blood  Internal respiration is the gas exchange process that occurs between the systemic capillaries and the tissue cells

13. Internal respiration, the exchange of gases that takes place between the blood and tissue cells is opposite to what occurs in the lungs.

What is hypoxia?  Hypoxia is inadequate oxygen delivery to body tissues. It is easy to recognize in fair-skinned people because their skin and mucosae take on a bluish cast (they become cyanotic)

Why is carbon monoxide dangerous?  Carbon monoxide competes vigorously with oxygen for the same binding sites on hemoglobin. It often displaces oxygen on the hemoglobin molecule. Therefore, oxygen is unable to be transported to the cells of the body.