Capillaries II Flashcards
Why is fluid exchange important
H2O for chemical reactions
Maintain circulation during haemorrhage
Abnormalities lead to oedema/tissue swelling
What is oncotic pressure
Pressure exerted by large molecules on membrane, which creates suction force to move fluid into capillary.
What is hydraulic pressure
Pressure exerted due to blood flow, where fluid moves across membrane into interstitial space
What is the equation for Starling’s principle of fluid exchange
Jv = LpA {[Pc - Pi) - sigma(Pip - Pii) }
or
Jv is proportional to {Hydraulic pressure difference (Pc - Pi) - Osmotic pressure difference (Pip - Pii)
where
Lp = Hydraulic conductance of the endothelium - how leaky the endothelium is to fluid
Sigma = Reflection coefficient = Fraction of the osmotic pressure that is exerted
A = Wall area
Pc = Capillary blood pressure
Pi = Interstitial fluid pressure
Pip = Plasma proteins
Pii = Interstitial proteins
What is lymphatic circulation
Returning excess tissue fluid/solutes back to the CVS
What helps lymphatic circulation
Lymph vessels have valves and smooth muscle. The contraction of the smooth muscle helps lymph flow, as well as surrounding skeletal muscle contractions
What does the overall control of extracellular fluid balance depend on
Capillary filtration
Capillary reabsorption
Lymphatic System
How do Starling’s factors determine changes in fluid balance
Circulation, interstitial fluid, lymphatic system
What is hypovolemia
Low capillary pressure - Caused by sympathetic nerve-induced vasoconstriction of pre-capillary arterioles leading to drop in downstream capillary pressure
What is oedema and what causes it
Excess of fluid within interstitial space, imbalance between filtration, reabsorption, lymph function
Caused by increased capillary pressure, decreased plasma protein oncotic pressure, inflammatory response and lymphatic problems
Describe low protein oedema
Not enough protein intake to make plasma proteins
Nephrotic syndrome: Urinary protein loss - Replaced by liver production
Liver disease: Not enough endogenous albumin produced
Describe inflammatory-mediated oedema
Swelling triggered by local chemical mediators of inflammation
Large increase in capillary permeability
Describe lymphatic obstruction
Filariasis/elphantitis - Nematode infestation, larvae migrate to lymphatic system grow/mate/form nests - block lymph drainage
Describe lymphatic removal
Lyphoedema - Caused by surgery to treat testicular cancer - removal of lymphatics
