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Purpose of heart and circulation move substances around the body.
Small organisms such as unicellular creatures substances move around the
organism by diffusion.
Diffusion the random net movement of particles from an area of high
concentration to an area of low concentration through a partially permeable
Mass flow all the particles in a liquid move in one direction through tubes
due to a difference in pressure.
Open circulatory system one pump of the heart pushes blood into the
cavities surrounding the animal's organs, then when the heart relaxes, the
blood is drawn back in.
Closed circulatory systems blood is enclosed in tubes and generates
higher blood pressure blood travels faster. Blood leaves the heart in arteries,
then arterioles to capillaries. Blood returns to the heart in venules then veins.
Valves ensure the flow in one direction. Animals with closed circulatory
systems are usually larger.
Single circulatory system Heart pumps deoxygenated blood to gills.
Gaseous exchange in the gills. Blood leaves gills, flows round the body
and returns to the heart.
Double circulatory system Right ventricle pumps deoxygenated
blood to the lungs to receive oxygen. Oxygenated blood returns to the
heart. Left ventricle pumps blood to the rest of the body. The blood
flows through the heart twice on one circuit round the body. Gives the
blood an extra boost reduces time, high metabolic rate.
The transport medium All in one direction in the circulatory system due to a
change in pressure mass flow .
Blood contains plasma and water and contains dissolved substances such
as digested food molecules, oxygen and carbon dioxide, proteins, amino
acids, salts, enzymes, hormones, antibodies and urea. Cells are also in the
Water polarity has an unevenly distributed
electrical charge hydrogen end slightly positive
and oxygen end slightly negative. Water is a
dipole (pair of equal and oppositely charged or
magnetised poles separated by a distance).
The slightly positive end is attracted to the
slightly negative part of another molecule
( hydrogen bonding ).
Many chemicals dissolve easily in water due to
dipole nature. Ionic substances (such as
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In sodium chloride, the negative Cl ions are
attracted to the positive hydrogen part of water, and the positive Na+ ions are
attracted to the negative oxygen, separating them in an aqueous solution.
Polar molecules also dissolve easily in
water said to be hydrophilic . Nonpolar
substances such as lipids are said to be
hydrophobic and do not dissolve in water.…read more
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Vena Cava vein that returns blood to the right atrium of the heart from the
Pulmonary artery the artery that connects the right ventricle of the heart to
the lungs deoxygenated blood.
Pulmonary vein the vein that connects the left atrium of the heart to the
Aorta the artery which carries the blood from the heart to all parts of the body
except the lungs.
Pulmonary vessels the blood vessels that connect the heart and the lungs.…read more
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Calcium salts and fibrous tissue also build up, resulting in a hard
swelling called a plaque . This means the artery loses some of its
3. Plaques cause the lumen of the artery to become narrower, making it
more difficult for the heart to pump blood around the body and can lead
to a rise in blood pressure. There is now a dangerous positive
feedback building up. Plaques lead to more raised blood pressure
which leads to more plaque etc.