1. The respiratory system’s primary function is the transport of oxygen and carbon dioxide between the environment and the tissues. 1. Ventilation is the movement of gas into and out of the lung. 2. Ventilation requires muscular energy. 3. The respiratory muscles generate work to stretch the lung and overcome the frictional resistance to airflow provided by the airways (airway resistance). 4. Lung elasticity results from tissue and surface tension forces. 5. The lung is mechanically connected to the thoracic cage by the pleural liquid. 6. Airflow is opposed by frictional resistance in the airways. 7. Smooth muscle contraction affects the diameters of the trachea, bronchi, and bronchioles. 8. Dynamic compression can narrow the airways and limit airflow. 9. The distribution of air depends on the local mechanical properties of the lung. 10. In some species, air travels between adjacent regions of lung through collateral pathways. Air flows into the alveoli through the nares, nasal cavity, pharynx, larynx, trachea, bronchi, and bronchioles. These structures constitute the conducting airways. Because gas exchange does not occur in these pathways, they are also known as the anatomic dead-space (Figure 45-3). Dead-space can also occur within the alveoli. This alveolar dead-space is caused by alveoli that are poorly perfused with blood, so that gas exchange cannot occur optimally (see Chapter 47). Physiologic dead-space is the sum of the anatomic and the alveolar dead-space. Let us define the portion of each VT that enters the alveoli as VA and the part that enters the dead-space as VD. Then: If each side of this equation is multiplied by respiratory frequency (f) as follows:
Overview of Respiratory Function
Ventilation of the Lung
Ventilation
Ventilation Is the Movement of Gas Into and Out of the Lung
The Respiratory Muscles Generate Work to Stretch the Lung and Overcome the Frictional Resistance to Airflow Provided by the Airways (Airway Resistance)
< div class='tao-gold-member'>
You may also need
Full access? Get Clinical Tree
Overview of Respiratory Function: Ventilation of the Lung
Only gold members can continue reading. Log In or Register a > to continue