AQA Biology, Lungs and Lung Diease. -Unit 1

Hope this is okay, i have just made notes from the Nelson Thornes textbook.

Comment if you want anything chnaging or added.

I'm using this for my revision, so good luck retakers !! =D

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  • Created on: 06-05-12 18:37
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Chapter 5 Lungs and Lung disease From AQA Nelson Thornes
4.1 Structure of Human gas-exchange system
In all aerobic organisms there need to be a constant supply of oxygen to release ATP during respiration. A
build of CO2 which needs to be removed could be dangerous if still left in the body.
The volume of O2 which is need and the amount of CO2 is large in mammals because:
- Large organisms with large volume of living cells.
- To maintain a high body temperature they need to have high metabolic and
respiratory rates.
This means lungs have been made as a specialised surface called lungs, to
exchange the gas with air and blood.
Mammalian Lungs
Lungs are located where they are because (inside the body):
- Air is not thick enough to support and protect the delicate structure.
- They would lose a lot of water and dry out.
The lungs are supported by bones called the Rib Cage; the ribs can move their
muscles to allow the lungs to ventilate. This also means that it can have a tidal
stream of air, and the air within in constantly replenished.
Main Parts
The lungs pair of lobed shaped, made up of tubes of bronchioles and which tiny air sacs called alveoli.
The Trachea a flexible airway which is supported by rings of cartilage, to stop it from collapsing on it when
air pressure changes (breathing in). The tracheal walls are made up of muscle lined with ciliated epithelium
and goblet cells. Goblet cells produce mucus which traps dirt particles and bacteria from being breathed in.
The cilium moves the mucus with dirt and organisms up to the throat and in to the stomach where it passes
down the oesophagus and in to stomach.
The Bronchi which is divided in to parts of the trachea, one leading in to each lung, they are similar structure
to trachea and also produce mucus to trap dirt. The bronchi are supported by the cartilage but as the
bronchi's get smaller so does the amount of cartilage.
The Bronchioles they are a series of subdivisions from the bronchi, the walls are muscles lined with
epithelial cells which they can constrict to allow air in and out the alveoli.
The Alveoli are minute air sacs, with a diameter of 100 micro-metres to 300 micro-metres these are at the
end of the bronchioles. They contain collagen and elastic fibres and lined in epithelium. The elastic fibre
allows the alveoli to stretch when they fill with air and spring back when they are breathing out. The alveolar
membrane is where gas exchange takes place.
4.2 The mechanisms of breathing
To maintain the diffusion of gases air has to be moved in and out of the lungs, this is ventilation. When the air
pressure in greater in the atmosphere and low in the lungs, air is forced in to the alveoli, this is Inspiration
(inhalation). When the air pressure is high in the lungs and low in the atmosphere then air is forced out expiration
(exhilaration). The pressure change is due to two sets of muscles:
- The diaphragm a sheet of muscle that separates the thorax from the
- The intercostal muscles which are between the ribs
* the internal intercostal muscles, which contraction leads to expiration.
* The External Intercostal muscles, which contraction leads to

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Chapter 5 Lungs and Lung disease From AQA Nelson Thornes
Breathing is an active process and it requires energy, it occurs:
- The external intercostal muscles contract whilst in internal in costal muscles relax.
- The ribs are pulled upwards and out, to increase the volume in the thorax.
- The diaphragm muscles contract causing it to flatten (this also increases the volume in thorax).…read more

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Chapter 5 Lungs and Lung disease From AQA Nelson Thornes
- The walls of the alveoli and capillaries are both really thin and the diffusion pathway is very short.
- Alveoli and capillaries have a very big surface area.
- Breathing movements constantly breathing movements constantly ventilate the lungs, and the heart
constantly pumps the blood around the capillaries, keeping a steep diffusion gradient. This ensures that there
is always being exchange.
4.…read more

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Chapter 5 Lungs and Lung disease From AQA Nelson Thornes
- More and better housing.
- Improved health facilities and housing.
- Better nutrition from food, so that the immune system is not weakened by a poor diet.
Other ways to control TB is through drugs, but this can take a long period of time to take them. So that is can
lead to mutations and the strain of M. tuberculosis no longer responds to the drug.…read more

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Chapter 5 Lungs and Lung disease From AQA Nelson Thornes
1 in 5 smokers will develop this in their lifetime, it develops after 20 years and so it is hard to diagnose it until
the lungs have been irreversibly damaged. In healthy lungs, there is a large amount of elastic tissue (elastin)
when expands and shrinks when we breathe in and out.…read more


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