Breathing and exchange surfaces-study guide

Covers all I've been taught in the breathing and exchange surfaces topic AKA unit 1:section 4

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Biology study guide- Exchange surfaces and breathing
Surface area: volume ratios
Calculation- surface area/ volume to get surface area compare to volume = 1
Smaller animals have a greater surface area to volume ration than larger animals.
A larger surface area to volume ratio allows for more exchange of substances.
Skin has a large surface area so that sweat can be evaporated.
Alveoli have a large surface area for gas exchange.
Villi have a large surface area for the exchange of nutrients into the intestine.
Exchange organs
only occur in multi cellular organisms
as in single cell organisms substances can diffuse directly into the cell.
In multicellular organisms this cant happen because some cells are too deep in the body and
that larger animals have a low surface are to volume ratio so it it difficult to exchange the
amount of substances required by diffusion.
Gas exchange
This occurs in the alveoli. Where oxygen goes into blood capillaries and CO2 leaves the
blood capillaries.
The gasses move by diffusion through the alveolar epithelium and the capillary epithelium.
The oxygen then goes into the hemoglobin in the blood.
The CO2 then enters the alveolar space so that it can be breathed out.
Tissues and their functions in Gas Exchange
Goblet cells and glandular tissue- secrete mucus which traps air particles which may contain
pollen or bacteria.
Ciliated epithelium- have cilia( like little hairs) which move in a synchronized movement to
move the mucus up the the back of the throat.
Smooth muscle- contract to constrict the airway. Constricting lumen can restrict the flow of
air in and out of the alveoli. This is what causes asthma.
Elastic fibres- when the smooth tissue relaxes the elastic fibres recoil to their original size
and shape. This helps to dilate the airway.
In the alveoli the allow the alveoli to stretch and prevent the bursting
Cartilage- for support in the trachea and bronchi, to prevent them collapsing during times of
low pressure.
Are effective exchange surfaces because;
-They have an enormous surface area.
-They have a moist lining
-Very thin walls( epithelium cells are only one cell thick)
-A large blood supply to constantly take away oxygen and bring in CO2 keeping
concentration gradient high
Inspiration-Active process
The Diaphragm contracts
The external intercostal muscles contract and lift the ribs up
These contractions allow for the lungs to expand
The pressure within the lungs decreases
The air is draw into the lungs due to the lower pressure compared to outside the lungs.

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Biology study guide- Exchange surfaces and breathing
Expiration- Passive process
The diaphragm relaxes
The external intercostal muscles relax lowering the ribs
These relaxations decrease the area of the lungs( compress the lungs)
Which increases the pressure inside the lungs
Forces air out of the lungs
Key Words
-Tidal volume- the volume of air moved in and out during breathing when at rest.
-Vital capacity- the largest amount of air that can be breathed in and out in one breath.…read more


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