El sistema circulatorio

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The blood circulatory system

1) Differences between red blood cells and white blood cells
|STRUCTURE |Only one kind of cell. |Several different kinds of cells |
| ||(phagocytes and lymphocytes being the |
| | |most numerous). |
| |Tiny, disc-like. |Larger than red blood cells (most of |
| | |them),varying shapes. |
| |No nuclei. |All have nuclei (of varying shapes |
| | |according to cell type). |
| |Spongy cytoplasm, carrying the red |Non-spongy cytoplasm, carrying granules|| |pigment haemoglobin. |(in some). |
| |Elastic cell membrane. |Non-elastic cell membrane. |
| |Maturation process in the red bone |Maturation process in the thymus, lymph|
||marrow. |nodes and spleen. |
|FUNCTIONS |Overall function: Gaseous exchange (as |Overall function: |
| |a part of the homeostatic function of |Defense of the body against both |
| |blood).|infectious disease and foreign |
| | |materials. |
| |Oxygen transport all throughout the |Collecting at the site of infection and|
| |body, carried as a combination with |engulfingand digesting harmful |
| |haemoglobin (oxyhaemoglobin). |bacteria, foreign particles and cell |
| | |debris (phagocytes). |
| |Carbon dioxide transport from the |Production and/or storage of antibodies|| |tissues to the lungs for it to be |(lymphocytes). |
| |exhaled; also bound to haemoglobin | |
| |(only small amounts, most of it travels| |
||in the plasma, either dissolved or as | |
| |sodium bicarbonate). | |

2. a) These steps of the heart beat take place in the following order:
iv) ventricles relax;
vii) semilunar valves close;
v) atria contract;
ii)blood enters ventricles;
vi) ventricles contract;
iii) tri- and bicuspid valves close;
i) blood enters arteries.

b) A person whose heart valves are damaged by disease is unable to take part in active sport because, if the heart valves are damaged, these are not able to carry out their function of stopping blood from flowing backwards. So, if they are not able...
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