Measuring Breathing Flashcards
ventilation
the movement of air into and out of the lungs
gas exchange
the ‘swapping’ of gases between the alveolar air and the blood
The lungs
The lungs are located within the upper part of your body called the thorax. They are surrounded by the ribcage and in between the ribs are intercostal muscles which play a role in ventilating the lungs.
When you inhale:
The intercostal muscles contract, expanding the ribcage outwards and upwards.
The diaphragm contracts, pulling downwards to increase the volume of the chest.
Pressure inside the chest is lowered and air is sucked into the lungs.
When you exhale:
The intercostal muscles relax, the ribcage drops inwards and downwards.
The diaphragm relaxes, moving back upwards, decreasing the volume of the chest.
Pressure inside the chest increases and air is forced out.
Mechanical Ventilation
When a person stops breathing on their own, mechanical ventilation can be used until the patient is able to recover and again breathe independently. This is done by machines called ventilators -
Negative pressure ventilators
the patient is placed in an airtight machine from the neck down, and a vacuum is created around the thorax. This creates a negative pressure, which leads to the expansion of the thorax and a decrease in pressure. As a result, air is drawn into the lungs. As the vacuum is released, the elasticity of the lungs, diaphragm and chest wall cause exhalation.
Positive pressure ventilators
air is forced into the lungs through a tube which is inserted into the trachea. As the ventilator pumps air in, the lungs inflate. When the ventilator stops, the elasticity of the lungs, diaphragm and chest wall cause exhalation.
Gas exchange
Within the alveoli, an exchange of gases takes place between the gases inside the alveoli and the blood.
Adaptations of the alveoli (1)
They are folded, providing a much greater surface area for gas exchange to occur.
Adaptations of the alveoli (2)
The walls of the alveoli are only one cell thick. This makes the exchange surface very thin - shortening the diffusion distance across which gases have to move.
Adaptations of the alveoli (3)
Each alveolus is surrounded by blood capillaries which ensure a good blood supply. This is important as the blood is constantly taking oxygen away and bringing in more carbon dioxide - which helps to maintain the maximum concentration gradient between the blood and the air in the alveoli.
Adaptations of the alveoli (4)
Each alveolus is ventilated, removing waste carbon dioxide and replenishing oxygen levels in the alveolar air. This also helps to maintain the maximum concentration gradient between the blood and the air in the alveoli.
