Objectives
- the relationship between flow pressure and resistance
- the effect the types of flow have on the circulation
- the basic law of flow - the law of poiseuille and its role in haemodynamics
- the factors what affect arterial blood pressure
- the factors that affect venous pressure
we need to maintain blood pressure for adequate perfusion flow depends on pressure gradient and resistance
the blood flow is
f = dP/R
hubs stuff on laminar flow and turbulent flow
peak speed in centre of vessel
shear stress is molecule sliding against each other highly increased resistance in turbulent flow
high shear stress can tear endothelium
reynold nmber relates velocity of blood flow diameter and density of blood as well as viscosity and determines turbulent vs laminar flow
Reynolds numebr is high in left bentricle aoric root exercise pregnancy anaemia
blood flow in capillaries is bolus
each rbc is lika a tamponade which pushed plasma around
sickle cell disease affects bolus transport as sickle form is hardened
Poiseuilles law
relates radius length and viscosity to resistance
radius is major factor in deciding resistance
pressure governing the blood flow
arterial blood pressure (this is what people talk about when they say BP)
IEL in the aortal wall this smooths flucutaions in the pressure and therefore flow
pulse pressure corresponsd to stroke volume and compliance
reduced in CHF Severe haemorrage aortic stenosus increased in trained athletes aortic valve stenosis arteriosclerosis
lots of values effect arterial BP