which type of blood vesels in the arm possesses vales

which type of blood vesels in the arm possesses vales

Answers
The arteries - Arteries carry blood AWAY from the heart, as a result the blood pulses through the arteries in response to the heart's beat. The radial artery on the inside of the wrist is often used in measuring pulse by counting the number of heartbeats in one minute. Any further help required please feel free to contact me :-)
smiledotcom
31 January 2013
Sorry... that answer was for your previous question.
smiledotcom
31 January 2013
The answer to this question is:- The veins - these carry deoxygenated blood back to the heart. Veins possess valves which are internal structures that prevent the backflow of deoxygenated blood, and permit the blood to flow only in one direction.
smiledotcom
31 January 2013
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How does tissue fluid return back into the circulatory system? ( AQA AS biology)


Q - How does tissue fluid return to the circulatory system?

In my textbook, it says the main reason is that it re-enters the capillaries by the loss of hydrostatic pressure within them, so by the time the blood gets to the venous end of the capillary the hydrostatic pressure is less within the capillary than outside them in the tissue fluid, so the tissue fluid is forced back into the blood in the capillary. However, when I look at mark schemes it says that it mainly re-enters by osmosis? How does it move in by osmosis? (I know that the remaining moves back into the bloodstream via the lymphatic system)

Answer

As the blood moves through the capillary it is getting further from the heart and pressure is being split between branches. This means hydrostatic pressure, and the force that attempts to push the fluid through the walls, decreases, However, osmotic pressure (basically how big the gradient of water potentials is) must get higher than hydrostatic pressure to ‘over power’ it. With nutrients moving out with the water, this means water potential would hardly be affected. However, there are special proteins in the plasma of the blood called plasma proteins. Being soluble (unlike may proteins) they alter water potential and being large (like many proteins) they are unable to cross the semi-permeable cell membranes of the capillary wall. As water moves out, the concentration of these proteins increases, and the water potential in the capillaries decreases. The gradient of water potential from outside to inside gets higher, as does the osmotic pressure. Eventually, osmotic pressure is higher than hydrostatic pressure, and fluid is forced back in! Any excess is returned via the lymphatic system, entering dead-ended lymphatic capillaries. This system of vessels eventually drains the excess fluid back into the circulatory system.