issue fluid
May 19, 2015
Tissue fluid
1. Exchange across the capillaries
2. Formation of tissue fluid
3. Lymph
Tissue fluid
• As blood flows through the capillaries some fluid passes out of capillaries
• This is tissue fluid it is very similar to plasma but does not have large plasma protein molecules in it
• This fluid bathes every cell in the body supplying them with glucose, amino acids, fatty acids, salts and oxygen
• (Tissue fluid also removes carbon dioxide an other waste material from cells)
Tissue fluid - formation
• As blood enters the narrow capillaries the build up of pressure forces water through the capillary walls into the cells.
• Other substances move out by diffusion
Tissue fluid - formation
Tissue fluid – exchange with tissues
Quick question – If you take out lots of water from a fluid but leave all the large plasma proteins in it, what happens to the water potential?
• As fluid leaves the capillaries the blood has lost a lot of its water and so it is far more concentrated (its water potential becomes more negative / lower)
• So water passes back into the capillary by osmosis
• Waste products leave the cells and enter the capillaries by diffusion
Tissue fluid - drainage
Tissu e f lu id hy d ro sta tic p ressu re = + 0 .4 5k P aTissu e f lu id w ate r p o te n tia l = – 0 .3 5 k P a
T issu e flu id
B lo o d h yd ro sta tic p ressu re = + 5 .2 k P aB lo o d w ate r p o te n tia l = – 3 .1 5 k P a
A rte rio le en d o fcap illa ry
Ven u le en d o fca p illa ry
• Not all the fluid returns to the blood capillary• 10% enters a separate system of microscopic
tubes called lymph capillaries• These are part of the lymph system• Lymph vessels have valves that let fluid enter
but not leave them• The lymph capillaries join to form lymph
vessels
Tissue fluid - Lymph
• Flow of liquid through the lymph system is very slow
• It depends on movement of our muscles, the valves in the vessels.
• Flow is in one direction only, from tissues back towards the bloodstream.
Tissue fluid
So… fluid• In the Blood is called plasma
• Surrounding the cells is called tissue fluid
• In the lymphatic system is called lymph
Tissue fluid
Tis
sue
flu
id
F rom arte ry
X
To v e in
T issu e ce lls
B lo o d cap illa ry
(i) Name the system to which the vessel labelled X belongs.
(ii)Describe the function of the vessels in this system. (2)
(i) lymph / lymphatic;
(ii)drains excess tissue fluid (because not all re-enters capillaries) / prevents accumulation of fluid ;returns fluid to blood;
W a te rpo ten tia lof p lasm a
M o ren eg a tiv e
A rte ria le n d
Ven o u se nd
D is tan ce a lo n g c ap illa ry
Explain what causes the decrease in water potential at the arterial end of the capillary. Explain what causes the increase in water potential towards the venous end of the capillary.
loss of water;(due to) hydrostatic pressure/blood pressure;explanation in terms of solute concentration / plasma proteins;2 max
water enters;due to osmosis / more negative water potential (in capillary);2