The respiratory system is formed by organs involved in breathing.

Breathing is a process that includes:

• Ventilation - exchanging air between the outer environment and the lungs;
• Respiration - exchanging gases (oxygen and carbon dioxide) between the outer environment and tissue and cells of the body. 

Before reaching the lungs, the air passes through the air passages, which include the nasal cavity, nasopharynx, larynx, trachea, and bronchi. Air in the air passages undergoes several transformations, including cleaning, warming, and humidifying.

The respiratory system is formed by the air passages and paired respiratory organs - the lungs.

The lungs are the most prominent organs of the respiratory system, and they are essential for respiration.

The respiratory system may also be called the respiratory tract, and it can be divided into two major parts depending on their position in the body. Mentioned parts are called the upper and lower respiratory tracts.

The upper respiratory tract includes the following structures:

• Nose and nasal cavity
• Paranasal sinuses
• Nasopharynx and oropharynx
• Larynx (above the vocal cords)

The lower respiratory tract consists of the following organs:

• Larynx (below the vocal cords)
• Trachea
• Bronchi

The lower respiratory tract ends with the lungs, which are covered by pleura - a thin and serous double layer of tissue that lines the thoracic cavity and covers the lungs.