The Respiratory System

The function of the respiratory system is to inhale the air we breathe, which allows oxygen to pass into the blood stream and waste products (carbon dioxide) to be removed from the blood stream and to be exhaled.

When you breathe in, air enters through the nose. The nasal cavity warms and filters the air we breathe before it enters the trachea. The trachea then divides into the left and right bronchi. The bronchi then divide into what are known as alveoli, which are small air sacs in the lungs. This is where the oxygen we breathe in enters the blood stream, and when we breathe out, this removes waste product (carbon dioxide) from the blood stream.

The air we breathe contains about 21% oxygen. The rest is made up of different gases. Our body uses approximately 5% of this oxygen, exhaling the remaining 16%.  Therefore what we exhale has sufficient oxygen content for the purposes of rescue breathing.

The Upper Respiratory Tract

The upper respiratory tract includes the nostrils, mouth, nasal cavity, throat (pharynx) and the voice box (larynx). The throat is the main passage for both food and air. It starts from the cavity at the back of the nose and mouth and extends down to where it divides into two separate tubes, the trachea and the oesophagus. The trachea allows the passage of air to and from the lungs.

The upper respiratory tract is the most common location for an airway obstruction.

When you breathe in, air enters through the nose. The nasal cavity warms and filters the air we breathe before it enters the trachea. The trachea then divides into the left and right bronchi.

The Lower Respiratory Tract

The lower respiratory tract consists of the trachea (windpipe), bronchi and lungs, which then divide into two, going into the left and the right lung. The bronchi then progressively divide into small bronchioles and eventually end up as alveoli and alveolar sacs which are small air sacs in the lungs. This is where the oxygen we breathe in enters the blood stream and when we breathe out this removes waste product (carbon dioxide) from the blood stream. The lungs fill most of the chest cavity, which is separated by the abdomen by a large sheet of muscle, known as the diaphragm.