Pressure And Flow In Arteries And Veins Flashcards
What are the different korotkoff sounds and what do they represent?
Silence - totally blocked vessel
Tapping - slightly opened vessel allowing flow of some blood
Thumping - partially opened vessel causing turbulent blood flow
Muffled - almost fully opened vessel
Silence - fully opened vessel allowing normal passive blood flow
What are the advantages and disadvantages of taking blood pressure using the korotkoff sounds?
Advantages is that its cheap and non invasive
Disadvantages is accuracy, discontinuous and needs care
What affects the pressure wave?
Stroke volume
Velocity of ejection
Total peripheral resistance
Elasticity of arteries
What is the drop in pressure as blood flows through the arteries?
95-90mmHg
What is the drop in pressure as the blood flows through the arterioles?
90-40mmHg
What is drop in pressure as the blood flows through the capillaries?
40-20mmHg
What is the drop in pressure as the blood flows through the veins and venues?
20-5mmHg
Is the pulmonary MAP the same as the systemic MAP?
No
The pulmonary MAP is a 5th of that of the systemic MAP
Where is blood velocity highest?
The aorta and other arteries
This is because they have the smallest surface area
Without extrinsic influences, why is the driving force of blood back to the heart low?
Because there is low pressure in the veins so the pressure difference is low
What are the main extrinsic influences which affect flow?
Gravity Venomotor tone Respiratory pump Skeletal muscle pump Systemic filling pressure
Describe how gravity affects flow.
Gravity causes an increase in pressure in the legs due to pooling of blood, so decreased pressure at the heart, therefore decreasing EDV.
Decreased EDV = decreased preload/SV/CO/MAP
This can cause orthostatic hypotension
Describe how the skeletal muscle pump affects flow.
When skeletal muscle contracts it queerest on the veins its surrounds which pushing blood through the veins.
Therefore lackage of movement can cause a thrombus formation (DVT) or varicose veins (build up of blood in the veins)
Describe how the respiratory pump affects flow.
On inspiration the diaphragm contracts to increase thoracic volume which causes decreased pressure in the thorax and increased pressure in the abdomen.
This pressure gradient runs through vessels which draws blood back to the heart via venous return
Describe how venomotor tone affects flow.
Contraction of the smooth muscle which surrounds veins and venues increases pressure to push blood up through the vessels.
