Simply, large tubular structures supported by cartilaginous rings called bronchi, divide several times to create smaller tubular structures called bronchioles. Bronchioles that have walls approximately one cell layer in thickness are called respiratory bronchioles; they terminate into hollow sacs of air called alveoli which are also approximately one cell layer thick. Blood is pumped to the lungs from the right heart via the pulmonary arteries which transition to capillaries that have an endothelium one cell thick. These capillaries surround the alveoli. There is a thin basement membrane between these structures. This thin walled interface is the site of gas exchange. Its thin structure is critical because gases are exchanged via passive diffusion which is driven by a concentration gradient on either side of the interface (1). Oxygen poor and carbon dioxide rich blood is pumped through the capillaries. The higher concentration of oxygen in the alveoli from ventilated air then attempts to equilibrate with the blood, by traversing the thin interface. Conversely, carbon dioxide in the blood moves off hemoglobin and into the alveoli where it is then expired out. An Alveolar pressure must be kept in order to keep the concentration gradient for the diffusion to occur. Breathing is what helps us maintain these concentration levels to allow for diffusion. Breathing is an …show more content…
This is accomplished by the rate of breathing and increasing the ventilation of more alveoli with fresh air. If the pH in the blood is to acidic, less than 7.35, respiratory centers in the brain described previously will cause hyperventilation, meaning that the rate of breathing will increase. This will allow more carbon dioxide to be removed from the blood since minute ventilation will increase. Removal of carbon dioxide makes the blood less acid. The opposite is true when the blood is more basic, greater than 7.45; respiratory centers will cause hypoventilation which will cause the body to retain carbon dioxide and make the blood more acidic. This phenomenon occurs to partially correct metabolic alkalosis and acidosis. Respiratory acidosis and respiratory alkalosis can be caused by disruption of normal physiologic homeostasis and ventilation perfusion mismatch