CV 2 Flashcards
Compliance is the arterials ability to:
~ Expand ( with age, vessels become less compliant )
~ Change in volume / Change in pressure
Distensibility is related to the arterial walls:
~ Elastic properties
~ Stress on a vessel
~ Decreased distensibility increases risk of arterial wall damage
~ ability to accommodate the pulsatile output of the heart
Veins are how many times more distensible than arteries?
8x
What are Control Conduits on Arterioles?
~ These “Pre-capillary Sphincters” determine where blood flow will go within the vasculature (open & close vessels, recruit vessels)
Circulation %: Pulmonary Vessels
9%
Circulation %: Heart
7%
Circulation %: Systemic arteries and arterioles
13%
Circulation %: Systemic capillaries
7%
Circulation %: Systemic veins and venues ( blood reservoirs )
64%
Cross-Sectional Area (cm squared) of the Aorta:
2.5
Cross-Sectional Area (cm squared) of the Small arteries:
20
Cross-Sectional Area (cm squared) of the Arterioles:
40
Cross-Sectional Area (cm squared) of the Capillaries:
2500
Cross-Sectional Area (cm squared) of the Venules:
250
Cross-Sectional Area (cm squared) of the Small veins:
80
Cross-Sectional Area (cm squared) of the Venae cave:
8
The smaller the cross sectional are the ________ the velocity
higher
Functional pressure:
~ Allows exchange to occur
~ capillaries, venules, small veins 17 mmHg
~ Mean PAP - 16 mmHg
~ Lungs - 7
Guyton’s 3 pearls of circulation
1: The rate of blood flow to each tissue of the body is almost always precisely controlled in relation to the tissue need
2: CO is controlled mainly by the sum of all local tissue flow
3: Arterial pressure regulation is generally independent of either local blood flow control or CO control
What are the main things that control the blood pressure?
Kidneys, and Nervous system
Arterial BP is controlled by:
~ CNS input (Squeeze & Beat)
~ Renal input (More or Less Fluid)
OHM’s Law
Flow = Change in Pressure / Resistance
( F = ΔP / R )
CO = how many L / min
5L / min
What is Parabolic Profile blood flow
When fluid at the center of the vessels moves faster than the fluid near the vessel wall due to friction
Laminar flow becomes turbulent when:
~ Rate of flow becomes too fast
~ Obstruction of a vessel
~ Sharp turns
~ Rough Surfaces
What are EDDY currents
Whirlpools
Turbulent tendency increases as what 4 things increase?
1: Velocity of blood
2: Diameter of the vessel
3: Density of blood
4: Viscosity of blood
Reynolds #
RE = VDP / viscosity
Reynolds # above 200-400
turbulent flow will occur at some branches of vessels
Reynolds # at 2000
turbulent flow will occur even at a straight smooth vessel
Density =
~ Mass / unit of Volume
~ ( temperature matters: gas vs liquid vs solid )
Viscosity =
Describes the friction between 2 layers of a given fluid ( e.g. RBCs and plasma )
What is blood pressure?
Force exerted by the blood against any area of a vessel wall
What is 70 mmHg in terms of measurment?
the force exerted by the blood can push a column of mercury against gravity up to 70 mm high
*** 1 mmHg =
1.36 cm of water
( 70 mmHg x 1.36 = 95.2 cm H2O )
mmHg vs cm of H2O
~ mmHg is the force needed to push a column of mercury agains gravity ____ mm high
~ cm of H2O is the force needed to push a column of water against gravity ____ mm high
*** SVR =. (equation)
([MAP-CVP]/CO) x 80
*** SVR is measured in
~ Dyne / sec / cm-5
~ Dyne: “The force required to accelerate a mass of 1 gram at a rate of 1 centimeter per second squared.”
Conductance is
~ The measure of blood flow through the vessel for a given pressure difference
~ Reciprocal of resistance
~ Conductance = 1/R
2/3 of total systemic resistance to blood flow is located:
in the small arterioles
Series / Serial resistance
~ Flow through each vessel is the same & the total resistance to flow is equal to the sum of the resistances in the vessel
~ R ( total ) = R1 + R2 + R3 + R4….
Parallel resistance
~ Flow through vessels which have branched extensively and permits each tissue to regulate its own blood flow independently of other tissues
~ 1/R (total )= (1/R1) + (1/R2) + (1/R3) + (1/R4)….
How are Arteries, arterioles, capillaries, venues, and veins arranged?
In series but when these branch, usually within the organs, the vessels are considered to be in parallel
As pressure in vessels increases what happens in relation to series/paralles resistance?
new vascular beds get recruited, further increasing parallel blood flow while maintaining a steady pressure
with increase in arterial pressur, rice of the blood through the vessel is increased resulting in compensatory increases in vascular resistance prompted by
local control mechanisms of the tissues (with a reduction in arterial pressure resistance is promptly reduced in most tissues and blood flow is maintained
Functions as an outer protective layer of the heart
Epicardium
Serous membrane that consists of connective tissue covered by epithelium
Epicardium
visceral layer of serous pericardium that that includes blood capillaries, lymph capillaries, and nerve fibers
Epicardium
Heart layer described as thick, largely consisting of cardiac muscle, arranged in planes separated by connective tissue that is richly supplied with blood capillaries and nerve fibers. “the force behind blood pumping out of the heart”
Myocardium
What layer of the heart: consists of epithelial and connective tissue that contains many elastic and collagenous fibers, lines all the heart chambers and valves, and is contiguous with the inner lining of blood vessels (endothelial cells)
Endocardium
The sac covering the heart, fibrous, tough, inelastic
Pericardium
Serous pericardium is how many layers?
~ 2 layers
~ Parietal layer - lines fibrous pericardium
~ Visceral layer - adheres to outside of heart (epicardium); space between parietal & visceral layer contains small amount of fluid
What is essential to coronary blood flow?
Afterload - needs a driving pressure to fill coronaries
Under normal conditions with constant perfusion pressure, what is the major determinant of coronary blood flow
Coronary vascular resistance
How much blood traverses the coronary arteries?
~ 4 - 5% of Total Cardiac Output
~ about 225 - 250mL / min
At what point is maximal LCA inflow
During early diastole ( during systole pressure compresses vessels on the LV )
At what point is maximal RCA inflow
During ventricular systole ( thin right ventricle contracts at a much lower pressure which does not compress the coronaries as much as the LV )
What equation determines Coronary Perfusion Pressure (CPP)
Aortic Diastolic Pressure - LVEDP = Coronary Perfusion Pressure
What is a normal CPP
15 - 70 mmHg
How high does CPP need to be during cardiac arrest in order to achieve ROSC
15 mmHg
What happens to CPP if there is an interruption in compressions?
There is a drastic call in CPP which takes time to rebuild
Define Compliance
The increase in volume when the pressure in that vessel has increased
Compliance = Volume / Pressure
Pulse Pressure equation
PP = SV / Compliance
PP = SBP - DBP
What is the PP in a normal healthy adult
40 mmHg
What do you see with Low pulse pressure ( < 30 mmHg )
~ Narrow pulse pressure
~ drop in SV or High SVR or both
~ Hypovolemia, cardiac tamponade
What do you see with High pulse pressure ( > 60 )
~ Wide pulse pressure
~ Increase in SV or low SVR or both
~ Atherosclerosis, AR, PDA
What is a norma CVP
~ 2 - 6 mmHg
~ -3 - +30
~ -3 mmHg = heart is pumping or severe hemorrhage ( think little blood in heart )
~ +30 mmHg = heart failure or post massive transfusion ( think too much blood in the heart )
What is gravities effect on BP
~ Legs +90 mmHg
~ Arms +35 mmHg (rib compression + gravity)
~ Neck 0 mmHg
~ Skull -10 mmHg
What can happen if the skull is open during surgery?
~ Hydrostatic suction
~ air can be sucked in to the venous system and may cause a venous air embolism in the heart (death)
How much blood volume can be lost from the circulatory system within 15 - 20 min of standing absolutely still?
10-20%
Even after ____% of total blood volume is lost, the venous reservoir helps the circulatory system function almost normally?
20%
Blood reservoirs: Spleen
100 mL of blood
Blood reservoirs: Liver
Several hundreds of milliliters
Blood reservoirs: Large abdominal veins
300 mL
Blood reservoirs: Venous plexus beneath the skin
Several hundreds of milliliters
Blood reservoirs: Heart
50 - 100 mL
Blood reservoirs: Lungs
100 - 200 mL
What is created of smooth muscle fiber that opens and closes the capillary entrance?
Precapillary Sphincters
The Capillary: Brain
Tight junctions
The Capillary: Liver
Wide junctions
The Capillary: GI
Somewhere between tight and wide junctions
The Capillary: Kidneys
Fenestre
What can the Lymphatic system be thought of as?
A drainage system
The Lymphatic system filters:
~ 2 - 3 L / day
~ 1/10th of fluid filtered from the arterial capillaries
~ Contains valves similar to veins
What is Lymph?
~ Fluid - has same composition as interstitial fluid
~ increases in protein concentration 3 - 5 g/dL in certain areas like liver and GI
~ 2/3 of lymph comes from thoracic duct ( liver and intestines )
Lymph rates of flow:
~ 100 mL/hr - thoracic duct
~ 20 mL/hr - lymphatic channels
~ 120 mL/hr total
What do increases in interstitial fluid pressure due to lymph flow if lymph vessels are working nomrally
Increases lymph flow
What determines lymph flow?
1: Interstitial fluid pressure
2: Activity of lymph pump - external factors that intermittently compress lymph vessels cause pumping ( movement of skeletal muscles, pulsation of arteries adjacent to lymphatics )
What is the role of the Lymph system?
To return fluids and proteins to the circulation ( controls protein concentration, volume and pressure in the interstitial)
What is the largest Lymph organ in the body
The Spleen
What is the structure of the spleen?
Encased in a connective tissue capsule extending inward to divide spleen into lobules
What 2 types of tissues is the spleen comprised of?
White pulp - T & B lymphocytes
Red Pulp - blood reservior
Blood flow through the spleen
Enters via splenic artery - moves through sinuses ( filtration ) - leaves through the splenic vein
What does the spleen do?
~ Plays a role in immunity by destroying pathogens in blood, creating lymphocytes in response to invading pathogens, engulfing cells with macrophages
~ Removes old and damaged RBCs from circulation
In what organ are sinuses present that during emergencies (hemorrhage) smooth muscle in vessels contract to squeeze blood into circulation?
Spleen
