Oedema and heart failure Flashcards
Why is the total cross section area high in capillary beds
Large surface area means functions can take place like gaseous exchange
What is the function of a precapillary sphincter
Cuff of smooth muscle fibres that surround the roof of each true capillary at the metaarteriole that act as a valve to regulate blood flow into the capillary
What important functions take place between capillaries and cells
- Removal of CO2 and waste products from cells
- Delivery of nutrients and oxygen to metabolising tissues
How is water distributed throughout the body with regards to extra / intracellular components
2/3= intracellular fluid 1/3= extracellular fluid (80% interstitial fluid and 20% blood plasma)
What does hydrostatic pressure exerted against the inner capillary wall cause
Promotes the formation of tissue fluid- net filtration pressure, out of the vessel
What is colloid osmotic pressure
osmotic pressure exerted by plasma proteins
Promotes fluid re absorption into circulatory system
What happens to the hydrostatic pressure difference as the length of the capillary increases
It decreases
What is Starling force
(Capillary hydrostatic pressure + Colloid osmotic pressure of interstitial fluid) - (Interstitial fluid hydrostatic pressure + Colloid osmotic pressure of blood plasma)
What is the net pressure at arterial end of a capillary
Net pressure filtration (pushing fluid out)
What is the net pressure at the venous end of a capillary
Net pressure absorption (fluid in)
What is an oedema
An excessive accumulation of interstitial fluid
What can cause oedema in relation to starling’s forces
- increased outward filtration
- decreased absorption
- leaky vessels
What could cause increased venous pressure
- Obstruction of vessels
- generalized increase in venous pressure i.e. heart failure
What could cause a decrease in absorption pressure
- Fall in plasma colloid osmotic pressure
- this could lead to protein loss and reduced protein synthesis
What could cause leaky vessels
- Local inflammation
- Vasculitis, inflammation of the blood vessels (usually a secondary disease)