The AlveoliThe Alveoli

Louis Holdcroft & Joel WillamsLouis Holdcroft & Joel Willams

AdaptationsAdaptations

The lungs Alveoli have many The lungs Alveoli have many adaptations to make it a lot more adaptations to make it a lot more effective for efficient gas effective for efficient gas exchange:exchange:

There are millions of AlveoliThere are millions of Alveoli

Alveoli have a large surface area Alveoli have a large surface area to volume ratioto volume ratio

They are very thin (1 cell thick)They are very thin (1 cell thick)

They are partially permeable so They are partially permeable so allow only selected materials allow only selected materials throughthrough

There is a movement of an There is a movement of an environmental medium and a environmental medium and a movement of an internal medium.movement of an internal medium.

The enviromental medium is the air and the internal medium is the blood.

Reasons for these adaptions:Reasons for these adaptions:They have a large surface area to They have a large surface area to volume ratiovolume ratio – This is because the – This is because the larger the surface area the more larger the surface area the more oxygen it picks up and speeds up the oxygen it picks up and speeds up the rate of gas exhange.rate of gas exhange.They are very thinThey are very thin – Because they are – Because they are only 1 cell thick this keeps the diffusion only 1 cell thick this keeps the diffusion pathway short and allows materials to pathway short and allows materials to pass through them rapidly. Aswell as pass through them rapidly. Aswell as this the red blood cells are slowed this the red blood cells are slowed down and therefore have more time to down and therefore have more time to pick up oxygen, making the gas pick up oxygen, making the gas exchange more efficient.exchange more efficient.They are partially permeableThey are partially permeable – This – This allows selected materials to diffuse allows selected materials to diffuse through easily.through easily.They have a net movement of an They have a net movement of an environmental and internal mediumenvironmental and internal medium – – There is a constant movement of blood There is a constant movement of blood around the capillaries of the alveoli and around the capillaries of the alveoli and a constant ventilation of air aswell, this a constant ventilation of air aswell, this maintains the concentration gradient for maintains the concentration gradient for efficient gas exchange.efficient gas exchange.

Role of environmental and internal Role of environmental and internal mediums in the lungsmediums in the lungs

In the lungs there are 2 mediums which help to increase gas exchange. In the lungs there are 2 mediums which help to increase gas exchange. Breathing movements constantly ventilate the lungs, this means that Breathing movements constantly ventilate the lungs, this means that there is always a supply of oxygen in the lungs which the red blood there is always a supply of oxygen in the lungs which the red blood cells pick up and get rid of CO2, this supply of oxygen maintains a cells pick up and get rid of CO2, this supply of oxygen maintains a concentration gradient for efficient gas exchange. The internal medium concentration gradient for efficient gas exchange. The internal medium is blood, the heart constantly pumps blood around the body, and is blood, the heart constantly pumps blood around the body, and around the capillaries in the alveoli. This blood is constantly arriving at around the capillaries in the alveoli. This blood is constantly arriving at the lungs and picking up the oxygen, together both of these mediums the lungs and picking up the oxygen, together both of these mediums insure that a steep concentration gradient of oxygen is maintained.insure that a steep concentration gradient of oxygen is maintained.

Constant blood flow Constant airflow

Facts of the alveoli:Facts of the alveoli:

Their total surface area is 70 Their total surface area is 70 metres squared, around half metres squared, around half the area of a tennis court.the area of a tennis court.Each alveolus is around 0.05 to Each alveolus is around 0.05 to 0.3 micro metres, which is very 0.3 micro metres, which is very thin.thin.The blood capillaries supplying The blood capillaries supplying them are around 7-10 them are around 7-10 micrometres in diameter and micrometres in diameter and have a wall of around 0.04 – have a wall of around 0.04 – 0.2 micrometres for efficient 0.2 micrometres for efficient gas exchange.gas exchange.

Real alveoli in the lungs.