Vascular physiology Flashcards
Whats the main function of blood circulation?
The function of circulation consists in fulfilling the requirements of the organism: transport of nutrients and oxygen towards the tissues, distribution of hormones, transport of waste from tissues, etc.
What do we need to maintain in the whole body?
In general, to keep the appropriate environment in all body fluids to maintain homeostasis.
Whats Hemodynamics?
HEMODYNAMICS studies the factors that participate in the regulation of blood flow through the cardiovascular system.
Define blood flow:
Volume of blood that passes through a given portion of a blood vessel
per time unit (ml, L/ h, sec, min).
On what does Hemodynamic depend on?
- blood flow
- blood pressure
- blood resistance
Whats the letter for blood flow?
F or Q
Name the formula of F(Q=
F(Q)= pressure gradient/ resistance
What does “directly proportional” mean?
Pressure difference between two given points of a blood vessel (pressure gradient = pushing force)
means: directly proportional
What does vascular resistance. mean?
Vascular resistance.
- Inversely proportional
Resistance = 8 ƞ L / p radius4
Whats p
blood viscosity
Whats L?
L = length
What does blood flow/ pressure gradient mean?
The difference in pressure between two points of the vasculature determines the flow, not the absolute value of the pressure
What does perfusion pressure mean? (important)
Perfusion pressure: the gradient between arterial blood pressure and venous pressure in a comparable location in
the vascular tree.
When does fluid only flow?
Fluid flows only if there is a positive pressure gradient
When does fluid Not flow?
If there is no pressure gradient, so no flow
On what does the flow depend on?
Flow depends on the pressure gradient
What’s blood flow or resistance?
The radius of the blood vessel is the most important factor that determines blood flow.
name the formula of resistance
alpha 1/radius^4
name the formula of flow
alpha 1/ resistance
When does the blood flow is gonna be faster?
- The smaller/ narrower the radius, the faster the flow
Think about the blood flow regarding the cardiac output:
- Movement of a volume (ΔV) per unit of time (Δt)
- Amount of blood that goes through a given point
in a given period of time (ml/min or l/min) - Healthy individual 5000 ml /min
State the F(Q) formula regarding the cardiac output
F(Q)= ΔV/ Δt
What’s hydrostatic pressure?
Hydrostatic pressure exerted by blood on the walls of a blood vessel.
On what factors depends the blood pressure?
- Cardiac Output (CO). - Blood volume.
- Vascular resistance.
Whats blood pressure?
- Is the force blood exerts against the wall of blood vessels.
• It produces distension of the wall of blood vessels.
• It produces movement of blood from areas with higher pressure to those with less pressure.
What’s blood pressure/ blood circulation?
- There is a loss of pressure as soon as blood exits the heart
- Aortic pressure depends on the contractile force of the left ventricle
- Pressure is being lost since blood exits from the left ventricle (approx. 110 mmHg) until it reaches the right atrium (0 mmHg).
What different effects do we have on peripheral or systemic resistance on BP?
The difficulty that blood has to go through blood vessels.
The resistance is determined by:
- Blood vessels
(vascular diameter, length) - Blood (viscosity)
Do we have a lower or higher resistance if we have a short vein?
A lower because the blood can go through faster
Anatomically wise on what does the artery contractility depend on?
On the developed media tunica
Define TOTAL peripheral resistance
The total peripheral resistance equals the sum of resistances within all blood vessels of the
systemic circulation.
Where can we find the mayor resistance?
In the arterioles
We have a blood flow through four identical vessels, how does the sum change?
The sum doesnt change, blood flow through four identical vessels is equal, total flow into vessels equal total flow
We have a blood flow through four different vessels but we constrict one of them, how does it change?
The total sum doesnt change, but the constricted one leave less blood through, whereas the others take this blood that in the end we get the same sum
How is the blood viscosity effected in blood pressure?
The higher the mass of formed elements in the blood or hematocrit, the higher the blood’s viscosity.
Name an example of less viscosity
anemia, less red blood cells, less viscosity
How can we increase the viscosity?
By Hematocrit
Can we find higher or lower viscosity in Polycythemia?
We find more viscosity
How is the blood pressure inside arteries conditioned?
Conditioned by the mechanical events within heart (systole and diastole)
Where can we find the highest arterial pressure?
Systolic blood pressure (SBP): The highest arterial pressure reached during ventricular systole (110-120 mmHg)
Where can we find the lowest arterial pressure?
Diastolic pressure (PBD): The lowest arterial pressure reached during ventricular diastole (70-80 mmHg)
How do we call the thing for listening the heart sound?
The Stethoscope
How do we call the thing we put on the arm?
The inflatable cuff
How do we call the thing we can observe the pressure numbers?
Pressure gauge
Can we hear the blood flow when the artery is no longer compressed?
no, the blood flow is silent
Over what artery do we have to place over the stethoscope?
Over the brachial artery
Through what are the Karotkoff sounds are created?
The sound are created by pulsatile blood flow through the compressed artery
Does the pulse pressure increase or decrease along the cardiovascular system? (differential pressure)
it decreased along the cardiovascular system, because the resistance and total surface increase
What do we understand about mean arterial pressure?
The value of arterial pressure achieved during a complete cardiac cycle
What does MAP stand for?
Mean arterial pressure
Where do we find the lowest mean arterial pressure?
In pulmonary veins
Where do we find the highest mean arterial pressure?
In larger systemic arteries
What are the factors that affect the mean arterial pressure?
- blood volume
- cardiac output
- Distribution of blood through arteries and veins
- total vascular (peripheral resistance)
What do we understand under blood volume?
- fluid intake
- fluid loss (passive, regulated by kidneys)
What do we understand under cardiac output regarding the hemodynamics?
- Heart rate
- stroke volume
Regarding the hemodynamics: what factor affects the distribution of blood through arteries and veins?
Diameter vessels
Regarding the Hemodynamics: what’s the factor that affect the total vascular (peripheral) resistance?
The diameter of arterioles
Where do we store blood?
The venous system brings blood from tissues to the heart and acts as a blood reservoir (60-70% of blood from the whole vascular system is stored in veins)
Can we contract veins?
NO, just arteries
How do we call veins that have walls with a high degree of distension?
Capacitance vessels
Why do we have capacitance vessels?
They contribute to the regulation of the volume of blood that circulates at any given time
What do we understand under efficacious volume?
the regulation of the volume of blood that circulates at any given time
State three main characteristics of veins:
- large diameter
- low resistance
- speed of blood flow is slower (but faster than within capillaries)
Where can we find more flexible and thinner walls?
in veins
Where are the elastic and muscular components less developed?
In veins
Whats the factor that is more developed in veins?
The connective tissue
Name 3 classifications of veins:
- venules and small veins: tunica intimac
- Medium and large caliber veins:
•(Venous valves: avoid backflow of blood away from heart.) - Arteriovenous anastomosis:
• Allow blood flow to pass from the arterioles into the small venules without passing through capillaries.
What’s venous pressure?
It is the force that blood exerts on veins. Lower than the arterial pressure. Can vary depending on the volume of circulating blood (venous return) and on venous distention.
Whats central venous pressure
Pressure in the right atrium (≈0 mmHg). It is due to the blood that flows from the main veins (cava- systemic). It depends on factors that modulate the venous return / capacity of the heart to eject blood
Whats Peripheral venous pressure?
It is the pressure that blood exerts on thoracic / extra thoracic veins. Its value varies depending on each
vein and the posture
We have 2 types of venous pressure:
- Central venos pressure
2. Peripheral venous pressure
Whats a venous return?
Volume of blood that circulates from the capillaries to the right atrium per unit of time (min), propelled by a mean pressure gradient of 10-16 mmHg.
State the formula of venous return:
Difference of pressure between venules (16 mmHg) and right atrium (0-5 mmHg).
Whats the advantage of venous return?
Allows return of blood to the heart.
When does venous return decrease?
It decreases when pressure in right
atrium increases.
Factors that contribute to venous return:
- Venous pump (valves)
- Muscular pump
- Respiratory pump (inhalation/ exhalation)
- vascular pump
- Arterial pulse
- cardiac pump
Venous return: relaxation
Relaxation: valves are open and blood flows towards the heart.
Venous return: leg muscles contract
Leg muscles contract:
contraction pushes blood up. Some blood goes down and closes distal valves.
Venous return: after muscle contraction
proximal valve closes due to fall of blood. Distal valve opens because the pressure in the foot is higher than in the leg
State inhalation.
the diaphragm moves down causing a negative pressure in the thoracic cavity. Blood moves to less compressed thoracic veins [there is a suction effect from heart through the vena cava].
State exhalation
reverse pressure. Valves prevent blood from flowing back
Arterial pulse
abrupt expansion of an artery that compress the adjacent vein, resulting in the propelling of the blood towards the atria.
Cardiac pump:
atrial suction during ventricular diastole (atrial emptying).
