Hemodynamics Flashcards
what is hemodynamics?
the forces that influence and regulate BP and blood flow
what are the different types of vasculature in the body?
- arteries
- arterioles
- capillaries
- venules
- veins
what is the structure and function of the arteries?
- very thick, can be very large diameters,
- have lots of smooth muscle and elastic tissue, endothelium and fibrous tissue
- function for movement of blood
- more blood movement than veins
what is the structure and function of the arterioles?
- smaller than arteries
- about the same size as venules but thicker
- have endothelium and smooth muscles
- this allows for the movement of blood toward the capillaries
what is the structure and function of the capillaries?
- very thin and small - only 1 layer of cells
- only have endothelium
- site of diffusion from the blood to the tissues back to the blood
- don’t contract
what is the structure and function of the venules?
- about the same size as arterioles
- don’t contract
- only have endothelium and fibrous tissue
what is the structure and function of the veins?
- largest in diameter
- not as thick as arteries
- has endothelium, elastic tissue, smooth muscle and fibrous tissue but less so than the arteries
the circulatory system consists of…
a central pump and several vascular beds organized in parallel to each other
- the overall resistance of the circuit depends on the individual resistance of each section
- if you increase resistance in one place, you have to decrease resistance somewhere else to maintain blood pressure in the body
flow of blood is dependent on the regulation of ________ and _________ in a closed loop.
pressure and resistance
how do the arteries function in the circulatory system and why is it important?
- they’re an elastic system
- are a pressure reservoir that maintains blood flow during ventricular relaxation
- if they did not maintain pressure, we would not be able to effectively pass blood through the body
how do the arterioles function in the circulatory system and why is it important?
- are able to change their diameter to change the resistance of that area
- this controls blood flow to places where it is necessary
- helps with direction
how do the capillaries function in the circulatory system and why is it important?
- they are super thin so they allow for diffusion of nutrients
- exchange between the blood cells
how do the veins function in the circulatory system and why is it important?
- they serve as an expandable volume reservoir
- more compliant (= easier to expand)
- more veins than arteries
how do you get blood to capillaries against resistance?
tissues in arteries enable expansion and elastic recoil will help keep pushing blood through the arteries into arterioles
- pressure reservoir
- in relaxation, pressure decreases and variable resistance regulators control diameter of arterioles
blood flow is dependent on…
PRESSURE GRADIENT
where is the highest point of pressure? lowest point?
highest = LV
lowest = RA
Hydrostatic pressure is…
pressure (associated with BP) exerted by fluid in all direction on the walls
- the pressure of a fluid in motion decreased with distance (pressure lost due to friction)
how does mean systolic blood pressure vary throughout the vasculature?
what is the primary driving force fr blood force?
mean arterial blood pressure
= the pressure reserved in the arteries during heart relaxation
at rest, the body tries to maintain MAPB, what happens if there are changes?
- if P changes?
- if CO changes?
- CO or PR can be altered to bring it back to normal
- changes in CO are balanced by changes in PR and vice versa
- ex: if blood loss occurs = decrease in CO then decrease in P – counteracted by increase in R
- ex: sudden increase in CO = decrease in R to maintain MABP = maintain pressure gradient
what factors determine blood flow?
cardiac output and MABP
what factors influence vascular resistance?
- length of the circuit
- viscosity of blood
- radius of blood vessel
According to Poiseuille’s equation, what are the relationships that affect cardiac output?
- increase of P or r = increase in cardiac output
- increase in viscosity or L = decrease in cardiac output
how is vascular resistance exerted in the body?
in parallel or series circuits
- the overall resistance of the circuit depend on the individual resistance of each section combined
what happens when there is sympathetic vasoconstriction?
= decreased radius
so R increased
blood flow decreases
– increase R here will lead to other areas decreasing resistance to maintain CO
what is flow rate (Q)?
- the volume of blood that passes a given point in the system per unit of time
- volume / time
what is velocity flow (v)?
- the distance a fixed volume of blood travels in a given period of time
- speed of flow
- the cardiac output should be the same but the size of the vessel alters the speed at which it travels
- faster in smaller vessels
what is the continuity principle?
- mass conservation
- the product of velocity and cross-sectional area is constant k
how does the velocity of blood flow relate to total sectional area of the vasculature?
- how does it vary in different vessels?
note: the capillaries are deemed a large cross sectional area because they are using the value of the combinations of all capillaries in a bed
what kind of conditions affect aortic and coronary blood flow?
- carotid stenosis (reduced radius)
- aortic coarctation
- atherosclerosis
