AQA AS Bio unit 1: The lungs and lung disease

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  • Created on: 27-05-13 18:19
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The lungs and lung disease
All aerobic organisms need a constant supply of oxygen to release ATP during respiration. Build ups
of CO2 need to be removed as they could be dangerous if left in the body.
In mammals a large volume of oxygen is needed because they have high metabolic rates to keep
body temperature high.
Parts of the respiratory system
The ribcage, Intercostal Muscles and the Diaphragm
These all work together to move air in and out of the lungs.
Made up of tubes of bronchioles and tiny air sacs called alveoli
A flexible airway which is supported by rings of cartilage to stop it from collapsing on it
when air pressure changes. The tracheal walls are made up of muscle lined with ciliated
epithelium and goblet cells. Goblet cells produce mucus which traps dirt particles. The cilia
move the mucus and dirt up to the throat.
The trachea splits into two bronchi which lead to each lung. They are similar in structure to
the trachea.
A series of subdivisions from the bronchi leading to the alveoli.
Small sacs where gaseous exchange takes place.
Capillaries surround the alveoli and oxygen from the alveoli diffuses into the blood and
carbon dioxide diffuses out of the blood and into the alveoli.
Diffusion of gases is rapid because:
o The diffusion distance is very small as the walls of the alveoli and capillaries are very
o There are many small alveoli which provides a large surface area
o The lungs are constantly ventilated and the blood is constantly moving through the
capillaries which ensure a steep concentration gradient is maintained.

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This is an active process and requires energy.
The internal intercostal muscles relax the external intercostal muscles contract.
The ribs are pulled upwards and outwards increasing the volume of the thorax
The diaphragm contracts, causing it to flatten which also increases volume of the thorax.
The increased volume results in a decreased pressure in the lungs.
Atmospheric pressure is greater than pulmonary pressure, so air is forced into the lungs.
This is a passive process and does not require much energy.…read more

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Once TB bacteria have entered the lung they:
1. Multiply in the lung tissues
2. This causes inflammation and white blood cells kill off most of the bacteria
3. The infected tissue within the tubercles dies which damages the exchange surface, causing
tidal volume to be decreased. This is called primary infection and is usually controlled within
a few weeks.
4. Some bacteria, however, remain in the lungs, dormant. Years later they re-emerge and cause
a second infection of TB called post-primary tuberculosis.
5.…read more

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Elastin helps the alveoli return to their normal shape after inspiration and expiration.
The alveoli cannot recoil, so the lungs tidal volume is decreased.
This causes shortness of breath and wheezing.…read more


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