Structure of the respiratory system Copy

The respiratory system consists of the following structures. These provide the passageway for air in and out of the body:

• the nose
• the naso-pharynx
• the pharynx
• the larynx
• the trachea
• the bronchi
• the lungs

The nose

The nose moistens, warms and filters the incoming air. Tiny hairs called cilia line the nasal cavities and filter the incoming air. Mucous membrane secretes a sticky fluid called mucus which helps to prevent dust and bacteria from entering the lungs.

The naso-pharynx

The naso-pharynx is the upper part of the nasal cavity behind the nose.

The pharynx

The pharynx (throat) lies behind the mouth and between the nasal cavity and the larynx.  The pharynx serves as an air and food passage but cannot be used for both purposes at the same time, otherwise choking would result.

The larynx

The larynx is a short passage connecting the pharynx to the trachea. The larynx provides a passageway for air between the pharynx and the trachea.

The trachea

The trachea or windpipe passes down into the thorax and connects the larynx with the bronchi, which pass into the lungs.

The bronchi

The bronchi are two short tubes, which lead to and carry air into each lung. They are lined with mucous membrane and ciliated cells; he mucus traps solid particles and cilia move the particles upwards, preventing dirt from entering the delicate lung tissue. The bronchi subdivide into bronchioles in the lungs. These subdivide yet again and finally end in minute air-filled sacs called alveoli.

The lungs

The lungs are cone-shaped spongy organs situated in the thoracic cavity on either side of the heart. The function of the lungs is to facilitate the exchange of the gases oxygen and carbon dioxide.

Respiration

Respiration is the process of inhaling oxygen and exhaling carbon dioxide.

Inspiration

• Diaphragm contracts – increasing volume of thoracic cavity, therefore lungs fill with air.
• External intercostal muscles contract pulling ribs up and outwards.

Expiration

• Air leaves lungs due to relaxation of diaphragm.
• When the body needs to force air out, the internal intercostal muscles contract.

There are three types of breathing:

Apical – shallow, this occurs when the person is stressed or excited. This type of breathing only uses the upper lobe of the lungs.

Lateral costal breathing – slow, deep breathing that uses the middle and upper lobes of the lungs.

Diaphragmatic breathing – deep and calming breathing which uses the upper, middle and lower parts of the lungs.