THE RESPIRATORY SYSTEM

  Breathing controlled by the respiratory system is a continuous process. Breathing consists of exchange of gases between the body and the air, by a process called respiration. The respiratory system in conjunction with the cardiovascular system provides oxygen to the body cells for energy and removes carbon dioxide from the body cells. 

In addition to providing for exchange of gases between the body and the air, the organs of the respiratory system are also responsible for producing sound and assisting in the body’s defense against foreign material. 

In medicine, pulmonology is the specialty that deals with diseases of the lungs and the respiratory tract. A pulmonologist is a physician who studies the diseases and conditions of the respiratory system and treats them. 

THE RESPIRATION PROCESS 

Respiration is the act of breathing: 

• Inhaling (inspiration) - taking in oxygen
• Exhaling (expiration) - giving off carbon dioxide 

Respiration is accomplished by 2 processes – external respiration and internal respiration. 

• Internal Respiration – Exchange of gases at the cellular level. It refers to the O2 requiring chemical reactions that take place in the mitochondria and are the chief source of energy in the eukaryotic cells. 

• External Respiration - At the level of the whole organism, it designates the process of taking in O2 from the environment and returning CO2 to it.

UPPER RESPIRATORY TRACT

The upper respiratory tract begins with the nose. It consists of the nasopharynx, the larynx, and the upper trachea.

 Air enters the body through the nares of the nose and the mouth. The nose is lined with mucous membranes that help to warm and filter the air as it enters the respiratory tract. Hair-like projections on the mucous membranes called cilia sweep dirt and foreign material toward the throat for elimination. 

Once air passes through the nasal cavity and paranasal sinuses, it reaches the pharynx or the throat.

 The pharynx is divided into 

• Nasopharynx, the upper portion located behind the nose 

• Oropharynx, the middle portion located behind the mouth 

• Laryngopharynx, the lower portion located behind the larynx.

The pharynx serves as common passageway for both air and food. During the act of swallowing, a small flap of cartilage called the epiglottis covers the opening of the larynx so that food cannot enter the larynx and lower airways while passing through the pharynx to the lower digestive tract. 

Larynx is the voice box containing the structures that make vocal sounds possible, i.e., the vocal cords. The vocal cords vibrate as air passes through the space between them, producing sound. This space is called the glottis. The larynx connects the pharynx with the trachea. The larynx is supported by nine cartilages, the most prominent of which is the thyroid cartilage at the front.