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26 Cards in this Set
- Front
- Back
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Single circulatory system |
Blood only passes through the heart once for each complete circuit of the body |
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Double circulatory system |
Blood passes through the heart twice for each complete circuit of the body |
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Pulmonary circulation |
The portion of the cardiovascular systemwhich carries deoxygenated blood away from the heart, to the lungs, and returns oxygenated (oxygen-rich) blood back to the heart
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Systemic circulation |
The part of the cardiovascular system which carries oxygenated blood away from the heart to the body, and returns deoxygenated blood back to the heart
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Closed circulatory system |
The blood is enclosed inside blood vessels |
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Open circulatory system |
The blood isn't enclosed in blood vessels all the time, instead it flows freely through the body cavity |
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What do valves do? |
They prevent blood flowing the wrong way The valves only open one way - whether they are open or closed depends on the relative pressure of the heart chambers If there's higher pressure behind a valve, it's forced open If pressure is higher in front of the valve, it's forced shut |
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Why does the left ventricle of the heart have a thicker, more muscular wall than the right ventricle? |
It needs to contract powerfully to pump blood all the way round the body The right side only needs to get blood to the lungs, which are nearby |
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Why do the ventricles have thicker walls than the atria? |
They have to push blood out of the heart whereas the atria just need to push blood a short distance into the ventricles |
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The cardiac cycle |
An ongoing sequence of contraction and relaxation of the atria and ventricles that keeps the blood continuously circulating round the body Firstly the ventricles relax and the atria contract Then the ventricles contarct and the atria relax Finally the ventricles relax and the atria relax |
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The cardiac muscle is myogenic |
This means that it can contract and relax without receiving signals from nerves |
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What's the function of the arteries? |
To carry blood from the heart to the rest of the body |
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What's the structure of the arteries? |
Walls are thick and muscular Elastic fibres - to cope with the high pressure produced by the heartbeat Folded inner lining - allows artery to expand, this helps to cope with pressure All arteries carry oxygenated blood except for the pulmonary arteries |
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What's the function of the capillaries? |
Exchange substances such as glucose and oxygen with cells |
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What's the structure of the capillaries? |
Arteries branch into capillaries Capillaries are the smallest blood vessel Walls are only one cell thick - for efficient diffusion Capillaries connect to veins |
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What's the function of the veins? |
To take blood back to the heart under low pressure |
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What's the structure of the veins? |
They're wider than equivalent arteries Have very little elastic or muscle tissue Veins contain valves to stop blood flowing backwards Blood flow by veins is helped by contraction of the body muscles surrounding them All veins carry deoxygenated blood except for pulmonary veins |
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Tissue fluid |
The fluid which surrounds cells in tissues It's made from substances that leave the blood e.g. oxygen, water and nutrients Cells take in oxygen and nutrients from tissue fluid, and release metabolic waste into it |
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Capillary bed |
The network of capillaries in an area of tissue Substance move out of the capillaries, into the tissue fluid by pressure filtration |
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Pressure filtration |
1. At the start of the capillary bed, nearest the arteries, the pressure inside the capillaries is greater than the pressure in the tissue fluid The difference in pressure forces fluid out of the capillaries and into the spaces around the cells, forming tissue fluid 2. As fluid leaves, the pressure reduces in the capillaries (pressure lower nearest veins) 3. Due to the fluid loss, the water potential at the end of the capillaries is lower than the tissue fluid, so some water re-enters the capillaries from the tissue fluid at the vein end by osmosis |
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How is excess tissue fluid returned to the blood? |
The smallest lymph vessels are the lymph capillaries Excess tissue fluid passes into lymph vessels - once inside, it's called lymph Valves in the lymph vessels stop the lymph going backwards Lymph gradually moves towards the main lymph vessels in the thorax Here it's returned to the blood near the heart |
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Haemoglobin |
A large protein with a quaternary structure Each chain has a haem group which contains iron and give haemoglobin its red colour Haemoglobin has a higher affinity for oxygen (each molecule can carry four oxygen molecules) In the lungs, oxygen joins to the iron in haemoglobin to form oxyhaemoglobin This is a reversible reaction |
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Partial pressure of oxygen |
A measure of oxygen concentration The greater the concentration of dissolved oxygen in cells, the higher the partial pressure |
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What does haemoglobin's affinity depend on? |
The partial pressure of oxygen Oxygen loads onto haemoglobin to form oxyhaemoglobin where there's a high partial pressure of oxygen Oxyhaemoglobin unloads its oxygen where there's a lower partial pressure of oxygen |
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Why does fetal haemoglobin have a higher affinity for oxygen than adult haemoglobin? |
The fetus gets oxygen from its mother's blood across the placenta By the time the mother's blood reaches the placenta, it's oxygen saturation has decreased (some has been used by mother's body) For the fetus to get enough oxygen to survive its haemoglobin has to have a higher affinity for oxygen If its haemoglobin had the same affinity for oxygen as adult haemoglobin its blood wouldn't be saturated enough |
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How does carbon dioxide concentration affects oxygen unloading? |
Most of the carbon dioxide from respiring tissues diffuses into RBCs and is converted to carbonic acid by the enzyme carbonic anhydrase The carbonic acid splits up to give hydrogen ions and hydrogencarbonate ions This increase in hydrogen ions causes oxyhaemoglobin to unload its oxygen so that haemoglobin can take up the hydrogen ions - this forms a compound called haemoglobinic acid The hydrogencarbonate ions diffuse out of the RBCs and are transported in the blood plasma When the blood reaches the lungs the low partial pressure of carbon dioxide causes hyrdogencarbonate and hydrogen ions to recombine into carbon dioxide The carbon dioxide then diffuses into the alveoli and is breathed out |
