Biology AS AQA Unit 1 Lung Disease

Made these notes for my year 12 summer exam to revise and read over. There are spelling mistakes in most of my files but due to the busy exam schedule I had no time to correct them (sorry).

Most files have more information than what is needed but I feel it helps you feel more confident walking into the exam if you have a greater knowledge background and may help when having to apply knowledge to questions. Good luck :)

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  • Created by: Chelcie
  • Created on: 02-09-13 12:37
Preview of Biology AS AQA Unit 1 Lung Disease

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Lung Disease
The volume of oxygen that has to be absorbed (and CO removed) is large in mammals because:
1) They are relatively large organisms with a large volume of living cells
2) They maintain a high body temperature and therefore have high metabolic rates and
respiratory rates
They are located inside the body because air is not dense enough to support and protect the delicate
structures and they would lose water and dry out.
The rib cage supports the lungs.
Intercostal muscles can move the rib which allows ventilation with a tidal stream of air.
Trachea ­ flexible airway supported by a ring of cartilage which prevents collapse as the air
pressure inside falls when breathing in. Walls are made of muscle, lined with ciliated
epithelium and goblet cells. Goblet cells produce mucus. Cilia move mucus up the throat to
either the stomach or the oesophagus.
Bronchi ­ divisions of trachea. Also produce mucus, have cilia. The larger bronchi have
Bronchioles ­ subdivisions of bronchi. Their walls are muscle lined with epithelial cells.
Muscles are for constriction to control the flow of air in and out of the alveoli.
Alveoli ­ air sacs at the end of bronchioles. Contain some collagen and elastic fibres. Lined
with epithelium also. Elastic fibres allow for stretch as they fill with air and then springing
back. The alveolar membrane is the gas-exchange surface.
To maintain diffusion gradient, air must constantly be moved in and out of lungs.
Inspiration... (Uses energy)
External intercostal muscles contract (while internal relax)
Ribs pulled upwards and outwards, increasing the volume of the thorax.
The diaphragm muscles contract, causing it to flatten, which also increases the volume of
the thorax.
Increased volume of thorax leads to reduction of pressure in lungs.
Atmospheric pressure is now greater than pulmonary pressure, so air is forced into the
Expiration... (Passive process)
Internal intercostals muscles contract (while external relax)
Ribs move downwards and inwards, decreasing the volume of the thorax.
The diaphragm muscles relax, causing it to return to upward domed position. This decreases
the volume of thorax.
The decreased volume of the thorax increases pressure in lungs.
As the pulmonary pressure is now greater than the atmospheric pressure, air is forced out
of lungs.

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Total volume of air that is moved into the lungs during one minute
Pulmonary ventilation (dm3 min-1) = tidal volume (dm3) x ventilation rate (min-1)
Large surface area to volume ration
To speed up rate of exchange
Very thin
Keep diffusion pathway short
Partially permeable
Allows selected materials to move through easily
There is movement of environmental medium
To maintain diffusion gradient
There is a movement of internal medium
To maintain diffusion gradient
Diffusion Surface area x diffusion concentration
Length…read more

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Spreads through air droplets.
The bacterium is resistant and can survive for several weeks once the droplets have dried.
TB is spread between family members/close friends/work colleagues as close contact for a while is
needed for transmission.
TB can also spread from cow to human as bacteria also infect cattle. Therefore milk may contain the
People of greater risk are those who are in close contact with individuals, work in long-term care
facilities, are from countries where TB is common, have reduced immunity.…read more

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Localised allergic reaction
Allergens stimulate asthma
One or more of these allergens causes which blood cells on the linings of the bronchi and bronchioles
to release histamine.
Causes airway linings to be inflamed.…read more


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