The respiratory tract is divided into the upper and the lower tracts. The upper
respiratory tract contains the nares, nasal cavity, pharynx, and larynx and the
lowertract consists of the trachea, bronchi, bronchioles, alveoli, and alveolar-
capillary membrane.
During respiration, air is inhaled and makes its way through the upper respi-
ratory tract and travels to the alveoli capillary membrane in the lower respiratory
tract, which is the site of gas exchange. Oxygen from the air attaches to the
hemoglobin of the blood while carbon dioxide leaves the blood and is expelled
through the lower and upper respiratory tracts during expiration.RESPIRATION
There are three phases of respiration:Ventilation
Ventilation is the process by which oxygenated air passes through the respiratory
tract during inspiration.Perfusion
Perfusion is when blood from the pulmonary circulation is sufficient at the
alveolar-capillary bed to conduct diffusion. In order for perfusion to occur,
the alveolar pressure must be matched by adequate ventilation. The presence of
mucosal edema, secretions and bronchospasm increase resistance to the airflow,
which results in decreased ventilation. Decreased ventilation causes a decrease
in diffusion.Diffusion
Diffusion is the process where oxygen moves into the capillary bed and carbon
dioxide leaves the capillary bed.COMPLIANCE AND THE LUNGS
There are two lungs inside the chest cavity. Each is surrounded by a membrane
called the pleura. Each lung is divided into parts called lobes. The right lung has
three lobes and the left lung has two lobes.(^254) CHAPTER 14 Respiratory Diseases