hemodynamics (physio) Flashcards
What are the cellular elements of blood?
Leukocytes, thrombocytes (platelets), erythrocytes.
Centrifuging separates hematocrit from plasma. A hematocrit measurement is routinely performed when a variety of pathologies are suspected (B12 deficiency, long-term blood loss, lung disease, etc). What is a normal hematocrit level?
40% in women and 45% in men
RBC count …….. WBC count.
>>
……….. is the cellular fraction of blood while………….. is the noncellular fraction.
Hematocrit plasma
Plasma mainly contains what?
proteins (colloid), lipids, phospholipids, neutral fats, electrolytes.
What are colloids?
molecules with MW > 30,000. In blood they are the proteins. They are considered suspended rather than dissolved in solution.
Blood colloids are proteins. ………….are associated with proteins.
Fats
The heart is a 2 stroke pump. The left side pumps into the systemic circulation. This is the………… pressure side of the circulatory system. Return is via veins. This is the…………. pressure side. The Right side of the heart pumps into pulmonary circulation.
high low
Systole
When ventricles contract.
Diastole
When ventricles relax.
Systemic circulation consists of…………… distribution to different organs.
parallel
When it comes to the histology of arteries and veins, the layers from the lumen side to outside are:
endothelium, elastic tissue, smooth muscle, fibrous tissue.
Veins have what relative to arteries?
- a thinner elastic tissue
- less smooth muscle
- inner valves to prevent backflow of blood
Why do veins need valves to prevent backflow?
Veins return blood to the heart AGAINST gravity.
How do varicose veins form?
Incompetent valves result in valves not properly sealing, and blood backflows and results in engorgement of the veins.
A variety of factors causes this. such as obesity or standing on your feet for long periods of time.
Capillaries lack what?
elastic, smooth muscle, and fibrous layers.
What are the 3 basic types of capillaries?
– Continuous capillaries: where endothelial cells touch each other. MOST COMMON.
– Fenestrated: which have a diaphragm over the fenestration, & are found in exocrine glands, renal corpuscle, and small intestine.
– Sinusoidal: found in the liver.
The sum of the cross sectional areas of all capillaries is substantially greater than all other compartments of the circulatory system! Where is the greatest volume of blood held though?
In the veins and venules (due to their compliance).
What are the 2 most widely used imaging modalities to assess the competence of a vascular bed, and what do they rely on?
computed tomography angiography & magnetic resonance angiography.
Both rely on IV infusion of contrast agents.
In steady state (over period longer than the cardiac cycle) flow in each section of the circulatory system must necessarily be the same. What does this mean?
flow in all the arteries combined is the same as that in all the capillaries combined which is the same as the combined flow in the veins.
What is the formula for resistance?
R= resistance
n= viscosity
L= length
r= radius
Alteration in radius is the basis for regulating blood flow. Why?
Resistance is inversely related to radius^ 4th power! So if you reduce the radius, you increase the resistance. Since F=ΔP/R, having a larger resistance means a lower flow.
When vessels are in series, the overall resistance is what?
The sum of the individual resistances.
When vessels are in parallel, is the overall resistance less than or greater than the individual resistances?
less than
Poiseulle’s law applies to laminar flow. Laminar flow occurs when each cylinder of fluid from that adhering to the vessel wall inward slips past each other. Flow rate……………. as we move from the wall to the center of the vessel.
increases
What is the equation for Reynolds number?
N(tiny R)= ρDv/viscosity
Where:
N(tiny R)= Reynold’s number
ρ= density
D = diameter
v = velocity
What does it mean when you can hear turbulent flow?
A problem! Heart murmurs can be readily heard when flow is turbulent and is indicative of valvular disease.
* Arterial bruts are symptoms of any of a variety of pathologies including stenosis.
Velocity is the distance blood flows/time (cm/min). Velocity is inversely proportional to vessel…………….
diameter
* The greater the diameter, the slower the velocity
What is the formula for compliance?
C=V/P
Where:
C = compliance
V = volume (ml)
P = pressure (mm Hg)
The veins are the unstressed volume (meaning……………………….) while the arteries are the stressed volume (meaning……………………….).
they hold a large volume of blood under low pressure
they hold a small volume of blood under high pressure
* Differences in elasticity of tissue is due to the amount of elastic fibers (elastin, elaunin, andoxytalan) in the vessel wall. Note that capillaries and venules don’t have any.
* The pressure in the aorta is pulsatile (going up during systole and down during diastole). It is dampened due to the high elastance of the arteries, and it is smooth in the……………………
* See diagram.
arterioles
The…………… of arteries prevents a drop in pressure in the arteries.
elastance (elastic recoil)
When we increase pressure with a blood pressure cuff, we block blood flow through brachial artery completely. Then, we slowly release the pressure. When the pressure inside the vessel equals the pressure of the cuff (well, just above the cuff pressure), this is when we get the measurement for systolic pressure and can start hearing………………. flow (aka Korotkoff sounds). Then, when the sound goes away, there is……………….. flow. This gives us our diastolic pressure reading.
turbulent
laminar
