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1.2.1 EXCHANGE SURFACES AND BREATHING

Single celled organisms, such as Amoeba, have a high surface area to volume ratio. This means that
they don't need a specialized exchange surface because they're so thin that gases are able to
diffuse in and out of them because it is a relatively short…

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Gaseous exchange in the lungs

The lungs are a large pair of inflatable
structures lying in the chest cavity. Air can pass
into the lungs through the nose and along the
trachea, bronchi and bronchioles. Each part
of this airway has adapted to its function of
allowing the passage of…

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A thin layer of moisture lines the alveoli. The moisture passes through the cell membranes from the
cytoplasm of the alveolus cells. As we breathe out, it evaporates and is lost. The lungs must produce
a product called a surfactant to reduce the cohesive forces between the water molecules. Without…

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The lungs are in the chest cavity and are protected by the ribs which surround them. Each lung is
covered by pleural membranes which secrete a lubricating fluid, allowing the lungs to inflate and
deflate without rubbing against the walls of the ribcage. There are intercostal muscles in between
the…

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The cartilage is in the form of incomplete rings or C-rings in the trachea, but is less regular in
the bronchi.
On the inside surface of the cartilage is a layer of glandular tissue, connective tissue, elastic
fibers, smooth muscle and blood vessels. This is often called the `loose tissue'.…

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Cartilage

The cartilage plays a structural role. It supports the trachea and bronchi, holding them open. This
prevents collapse when air pressure inside is low during inhalation. The cartilage does not form a
complete ring (c-ring) so that there is some flexibility. This allows you to move your neck without…

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Breathing

Inspiration (breathing in)
If the air is to enter the lungs, then the pressure inside them must be lower than the
atmospheric pressure.
The external intercostal muscles contract and the internal intercostal muscles relax,
raising the ribs upwards and outwards.
At the same time, the muscular diaphragm contracts and…

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SPIROMETER

A spirometer consists of a chamber filled with oxygen that floats on a tank of water. A person
breathes from a disposable mouthpiece attached
to a tube connected to the chamber of oxygen.
Breathing in takes oxygen from the chamber,
which then sinks down. Breathing out pushes air
into…

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Residual volume is the volume of air that always remains in the lungs, even after the biggest
exhalation possible. Usually around 1.5 dm3
Dead space is the air in the bronchioles, bronchi and trachea. There is no gas exchange between this
air and the blood.
Inspiratory reserve volume is how…

Comments

L.Brady

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amazing, really useful! thanks

ellen

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do you have these kind of notes for unit 2?

Swallowtail

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These are a superbly written set of notes with coloured annotated diagrams on the respiratory system and the circulatory system. Although written for the OCR specification they would be useful to any biology student needing to study these topics for their specification. Team these up with a set of flashcards and a quiz or two for a complete set of resources.

Ross Bonnel Loves Kids and You

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"These are a superbly written set of notes with coloured annotated diagrams on the respiratory system and the circulatory system. Although written for the OCR specification they would be useful to any biology student needing to study these topics for their specification. Team these up with a set of flashcards and a quiz or two for a complete set of resources."

- Cunt, 2014

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