Human Respiratory System
The respiratory system sustains tissue functions in the human body by facilitating the efficient
exchange of oxygen and carbon dioxide with the external environment.
General Functions of the Respiratory System
The respiratory system fulfills its roles through pulmonary ventilation, external
respiration, gas transport, and internal respiration.
Pulmonary Ventilation – This is also called breathing; this process is the mechanical
movement of the air into and out of the lungs.
External Respiration - This phase refers to the exchange of gases that occurs
between the alveoli and the pulmonary capillaries.
Transport of Gases - This phase involves the circulatory system, which
transports gases between the lungs and tissues.
Internal Respiration - This phase refers to the exchange of gases that occurs
between the blood and body tissues.
2 Zones in Human Respiratory System
The conducting zone. It serves as the passageway of air into the lungs.
The respiratory zone. This consists of structures that facilitate the actual gas exchange.
Moving on, the respiratory system aids in the respiration process. It can be anatomically
divided into the upper and lower respiratory tracts.
Upper Respiratory Tract includes the:
NOSE - This structure serves as the primary entrance of air into the respiratory tract. It
also helps moisten, warm, and filter the incoming air. Its primary opening, the nostrils,
lead to the nasal cavity, the inner chamber.
NASAL CAVITY - The nasal cavity consists of nasal hairs (vibrissae) and cilia, both of
which filter the air.
PHARYNX - The throat serves as a passageway for both air and food into the
esophagus.
EPIGLOTTIS - This cartilaginous structure helps close the entrance to the trachea when
swallowing food.
LARYNX - This structure helps in sound production and also protects the trachea from
food aspiration.
Lower Respiratory Tract refers to the following airway structures:
TRACHEA - The windpipe connects the larynx to the rest of the lungs. It consists of cilia
that help propel debris-containing mucus back into the esophagus.
BRONCHI - These two branches penetrate into each of the lungs as they originate from
the trachea. Each bronchus consists of cartilage and smooth muscles that prevent it
from collapsing. The bronchi branch up to approximately 23 times to form the smaller
bronchioles.
