Lecture 11 – Capillaries II: Fluid exchange Flashcards
Importance of fluid exchange (3)
Normal physiological function - water for chemical reactions
Fluid re absorption from tissues to blood can maintain during haemorrhage
Abnormalities in fluid exchange can ,end to oedema/tissue swelling.
Fluid movement at the capillary wall (3)
Semi permeable membrane
Fluid moves across membrane into interstitial fluid via hydrostatic/hydraulic pressure.
Large molecules can’t pass through so they exert an osmotic/oncotic pressure which creates a suction force to move fluid into capillary.
increase in H pressure and decrease in O leads to excess filtration and oedema.
4 pressures determine filtration rate
FC
Starlings principle of fluid exchange
FC
Lymphatic circulation (3)
Returns excess tissues fluid back to the CVS. About 8 litres a day are filtered.
Lymph flow can be affected by lymph valves/SM/skeletal muscle contraction and relaxation.
Tissue fluid will be forced out of the capillaries due to hydrostatic pressure, this surrounds the tissues forming lymph and is absorbed into the lymphatic capillaries, it returns to the blood stream via drainage through the vena cava.
Lymphatic circulation - control of EC fluid balance depends on (3)
Capillary filtration
Capillary reabsorption
Lymphatic system
Lymphatic circulation - Starlings factor determine fluid balance (3)
Circulation
Interstitial fluid
Lymphatic system
Lymphatic problems (2)
Normal drainage
E.g. drainage elephantitis nematode infestation grow mate and form nests in the lymphatic system
Lymphoedema
Caused by surgery
Lymph nodes may be removed to prevent it from further spreading in the body.
Functions of capillaries (2) mechanism (2)
Solute exchange - nutrients of tissues, hormones and drug delivery
DIFFUSION obeys Ficks law
Fluid exchange - regulation of plasma and interstitial fluid volumes
BULK FLOW all molecules together pressure gradients across wall obeys Starlings principle
