Overview of circulation- Exam 2 Flashcards
Characteristics of pulmonary circulation
Systolic pulmonary artery pressure= 25 mm Hg
Pulmonary diastolic pressure= 8 mm Hg
Functional parts of circulation
Arteries transport under high pressure
Arterioles control conduits
Capillaries gas and nutrients exchange
venules and veins used for storage
Blood distribution in body
84% of blood in systemic circulation
16% of blood in pulmonary circulation
84% of Blood distribution in systemic circulation
64% in veins
13% in arteries
7% in arterioles and capillaries
What is the velocity of blood flow?
Volume of blood flow by area
V= F/A
Faster in arteries than veins
Very slow in capillaries due to gas and nutrients exchange
Functional principles of circulatory system
Rate of blood flow controlled by tissue need
cardiac output controlled by sum of local tissue flow
A.P. regulation independent of cardiac output and local blood flow control
Control of blood flow rate by tissue need
Micro vessels monitor tissue needs
Product accumulation acts directly on local blood vessels
local blood vessels dilate or constrict in response
Control of cardiac output by local tissue flows
Heart responds to demand of tissues
Heart can enroll help of nerves signals to pump required amount of blood
Factors determining blood flow
Pressure gradient
Resistance
F= Delta P/ Resistance
Cardiac output at rest = 5000 ml/min
What are the types of flow
Laminar (streamline) flow
turbulent flow
Characteristics of laminar flow
Blood flows @ steady rate and in streamlines
Blood vessels long and smooth
Characteristics of turbulent flow
Non layered flow
Creates murmurs
Produce more resistance than laminar flow
Proportional to velocity of blood flow, vessel diameter and density
Inversely proportional to the viscosity of blood
Blood viscosity
Property of blood to adhere to vessels walls and to each other
Based on number, shape and size of RBC
Blood more viscous than water (relative value=4.5)
Blood density
Blood heavier than water (specific gravity=1.055)
Depends on proportion of components particularly RBC and its proteins
What is Reynolds Number?
Measure of the tendency for turbulence to occur
Re=(velocity.diameter.density)/ viscosity
Re>200-400–>Turbulence will occur in some regions
Re> 2000—–> Turbulence will occur even in straight vessel
What is Blood Pressure?
Force exerted by the blood against any unit area of the vessel wall.
measured with a mercury manometer or with electronic transducers
What is Resistance?
Impediment to blood flow in a vessel
Indirectly calculated from measurements of blood flow and viscosity of blood
R=Pressure/(volume/time)
Variables determining resistance
Vessels radius: most important variable
Blood viscosity
Vessel length
Effects of resistance
Increase resistance—> Increase upstream pressure, Decrease of blood flow and downstream pressure
Decrease resistance—> Decrease upstream pressure, Increase blood flow and downstream pressure
Values of resistance
Resistance of entire systemic circulation = 1PRU
Total peripheral resistance up to 4 PRU in strongly constricted vessels.
Total peripheral resistance as low as 0.2 PRU in greatly dilated vessels
Resistance in the pulmonary system
Mean pulmonary arterial pressure= 16 mm Hg
Mean left atrial pressure=2 mm Hg
Resistance R=14/100= 0.14PRU
What is conductance?
Measure of blood flow through a vessel for a given pressure difference.
Each tissue contribute to overall conductance
Exact reciprocal of resistance
Arrangement of vessels
Arterioles, capillaries, venules and veins arranged in series
Parallel circuits formed supply blood throughout body
Circulations arranged in parallel
Brains Gastrointestinal
kidney Skin
Muscle Coronary circulation
Consequences of amputation
Removes parallel circuits
Reduction of total vascular conductance
Reduction of total blood flow
Increase total peripheral vascular resistance
Determinant of blood viscosity
hematocrit
Anemia decreases viscosity
Polycythemia increases viscosity
Blood flow autoregulation
Arterial pressure changes between 70-175 mm Hg
Vascular resistance adjustment and maintenance of normal blood flow done within AP parameters
Characteristics of systemic circulation
Arterial pressure between 120-70 mm Hg (systolic-diastolic)
Arterial pressure drops to 0 at vena cava termination
Systemic capillary pressure from 35-10 mm Hg
What are the causes of turbulent flow?
Blood flow is too great
Blood passes obstruction within the vessel
Blood makes sharp turn
Blood passes over rough surface
