It comprises several organs whose function is to transport air to and from the lungs, It contains a conducting zone consisting of a series of branching tubes which form the airways

The smallest branches of the respiratory system airways end in alveoli, The smallest branches of the respiratory system conducting zone end in alveoli

It takes place in the alveoli (microscopic air sacs), It takes place in the alveoli which provide a large exchange surface, It takes place in the alveoli consisting of thin membranes, covered with the extensive capillary network of the pulmonary circulation

The blood that exits the lungs via the pulmonary arteries is rich in oxygen

The blood in pulmonary veins – high O2 – low CO2, Alveoli – thin-walled sacs – large exchange surface, The blood in pulmonary arteries – high CO2 – low O2

It belongs to the conducting zone of the respiratory system, It has an external part consisting of cartilage and skin, It has two internal parts called nasal cavities, It represents the normal entry way of air in the respiratory system

The nasal choanae enable the communication between the nasal cavities and the nasopharynx, The nose is responsible for heating, humidifying and filtering air, The external nares (nostrils) are openings of the nasal cavities to the external environment

They represent the internal part of the nose, They communicate with the external environment through the nostrils, They are lined by a mucosa whose inflammation is called rhinitis

The frontal sinus inside the bone bearing the same name, The inferior nasal concha which delimits the inferior meatus, The nasal vestibule, in the ventral part of the nasal cavity

It contains blood vessels which warm cold air, It secretes mucus which humidifies dry air

They open into the nasal cavities, They decrease the weight of the cranium and serve as resonance chambers, They are lined with a mucosa which continues the mucosa of the nasal cavity

The nasal cavity is associated with the olfactory sense, The olfactory region is situated in the upper wall of the nasal cavities, The blood vessels in the nasal mucosa warm up cold air

The oropharynx, situated posterior to the oral cavity, The oropharynx where the digestive and respiratory tracts meet, The laryngopharynx, situated posterior to the larynx, The nasopharynx, situated posterior to the nasal cavities

It belongs to the airways and it has a cartilaginous structure, It is a passageway of air from the pharynx to the trachea, It is involved in the production of sounds

It is involved in the production of sounds, It joins the pharynx and the trachea at the level of the cervical vertebrae, It houses the vocal cords

Larynx – shorter vocal cords – children, Larynx – women – higher-pitched voice, Larynx – thyroid cartilage – more visible in men

It branches in two main bronchi, It continues the larynx, It is lined with ciliary cells which filter air before it enters the bronchi

They belong to the conducting zone of the respiratory system, together with the pharynx, bronchi and bronchioles, The larynx continues with the trachea. A semi-rigid tube, The mucosa lining the trachea contains ciliary cells which filter the air before it enters the bronchi

They are kept open by some cartilaginous rings situated in the posterior part, They belong to the bronchial tree, They result from the branching of the trachea

They are microscopic air sacs, approximately 300 million for each lung, In the alveoli, O2 from the air is exchanged for CO2 from the blood by a passive diffusion process, The respiratory membrane of alveoli forms an extremely thin barrier which allows the passage of respiratory gases

The nasal cavities, the larynx and the trachea belong to the airways and they are lined with mucosa, The branches of the trachea, bronchi and bronchioles form the bronchial tree of the lung, The larynx has true vocal cords and false vocal cords (ventricular folds)

Is based on the principle according to which air travels from a high-pressure area (high density) to a low-pressure area (low density), Is the process by which air flows in and out of the alveoli, Belongs to the breathing process, together with gas exchange

Inhibits the activation of the respiratory control centre, Determines the decrease of the respiratory rate and amplitude

Oxygen passes from the alveoli into the bloodstream, to be transported to the cells, Carbon dioxide passes from the bloodstream to the alveoli, to be expelled by breathing