Heamodynamics and microcirculation Flashcards
What is Total Peripheral Resistance? TPR
resistance to flow of blood in systemic circuit
What does MAP equal?
Cardiac output * TPR
What is Darcy’s Law?
flow is linearly proportional to pressure difference between 2 points
What is mean velocity?
Flow/ Total cross sectional area
What are the 3 types of blood flow in vessels?
Laminar- arteries/veins
Turbulent
Single file flow - capillaries
Where does turbulent flow occur?
ventricles
What is TPR equation?
8nL/ Pir^4
L- tube length r= radius
n= fluid viscosity
What is Poiseuille Law equation for Fluid Flow? Q
Pressure difference/Resistance
How are vessels of the same type arranged ?
Parallel but aorta/Pulmonary trunk arent
When does total resistance in circuit increase?
when series unit added
What is Compliance?
Volume/ change in distending Pressure
What is distending pressure?
pressure inside minus pressure outside
Why is artery a shallow gradient on Compliance graph?
when pressure applied, volume doesn’t increase by much
Why does Vein have large compliance?
thin walls and store volume well
What is LaPlace equation for Tension?
T= Pt *r/ u u= wall thickness Pt= trans mural r= radius
What is Trans Mural pressure ? Pt
pressure along entire wall
What is Autoregulation?
adjustment of blood flow to specific tissue
How is blood flow changed?
diameter of arterioles change
Alter contraction of sphincters
How is oxygen a factor of metabolic autoregulation?
hypoxia when not enough 02 to meet metabolic demand
How is low 02 supply increased?
Arteriolar smooth muscle vasodilate
What happens in vasodilation?
resistance decreases so inc. blood flow so inc. 02
What metabolic products diffuse into surrounding tissue and relax smooth muscle?
CO2
H+
Adenosine
K+
What substances in endothelium mediate vasodilation in smooth muscle?
Prostacyclin
Nitrogen oxide- Endothelium derived relaxing factor
What happens when Perfusion Pressure increases?
inc. stretch of smooth muscle> constriction>inc. Resistance so decreased flow then NEG. feedback
What is long term autoregulation of low 02 delivery?
increase Microcirculatory vessels
enlargement of vessels
What is an example of when long term autoreg.?
high altitudes
What do clefts in capillary endothelium allow?
hydrophobic solutes
water/ ions
How is exchange of fluid between capillaries and tissues?
- hydrostatic pressure highest at arterial end
- net osmotic pressure gradient favours fluid absorption by capillary
What is net fluid movement?
- fluid out at arterial end
- fluid in at venous end
What is lymph ?
fluid with white blood cells and waste
What are lymph nodes in the head?
Parotid
Submental
Submandibular
What carries excess fluid from capillary beds?
lymphatic vessels w/ smooth muscle to venous system
What does right lymphatic duct drain into?
internal jugular vein
What does left lymphatic duct drain into?
Subclavian vein
