Week 5 Flashcards
Pressure is used for ___.
In solids, the quantity force per unit area is referred to as ___.
Pressure is used for gases or liquids
In solids, the quantity force per unit area is referred to as stress.
Pressure is measured in
Newton’s per square meters, i.e. Pascal.
1 mmHg is equal to
0.133 kPa
Fluid -
A substance in the liquid or gas phase.
For fluids at rest, the shear stress is
zero
Intermolecular bonds are strongest in
solids
Intermolecular bonds are weakest in
gases
Body of fluid is not able to resist a shearing force exerted on its surface, so it…
must keep deforming when subjected to it.
When the pressure in the cuff exceeds the systolic pressure,
there is no blood flow to the lower arm and, consequently, no sounds.
When the pressure in the cuff is lowered with the release bulb to just below the systolic
pressure
there is intermittent flow, which is turbulent and produces gurgling sounds called the Korotkoff or K sounds.
Korotkoff or K sounds -
gurgling sounds produced by intermittent turbulent flow when the cuff P is lowered just below systolic P
As the cuff pressure is lowered further, K sounds…
get louder and then lower and are heard until the cuff pressure decreases to the diastolic pressure
Blood flow is not interrupted when the cuff P is less than the diastolic pressure
and the K sounds cease because the blood flow is no longer turbulent
The onset of the K sounds denotes
the systolic blood P
The end of the K sound denotes
the diastolic P
The brain contains approximately how much cerebrospinal fluid (CSF)?
150 cm3
Increased pressure causes the skull to
enlarge (hydrocephalus)
The pressure in normal eyes ranges
from 1.6 to 3 kPa
glaucoma -
the pressure increases in the eyeball, it can restrict the blood supply to the retina and it affects vision.
Cystometry
clinical diagnostic procedure which is used to measure forces in the bladder
The result of cystometry
cystometrogram, which plots the volume of liquid
against intravesicular pressure
Law of Laplace
gives the relation between the pressure within the lumen of a vessel (ΔP), the tension in the wall (T) and the vessel radius (R):
T=deltaP*R
equation of continuity
statement of the conservation of mass during flow
What can we understand from equation of continuity?
In steady state, the same mass flows into a volume and leaves it
Bernoulli’s equation relates blood pressure (P), and blood flow velocity (v)
If pressure losses due to friction or turbulence are neglected, Bernoulli’s equation states that:
“the sum of fluid mechanical energy (Pressure energy), P, fluid kinetic energy ½ρv2, and fluid
potential energy, ρgh, stays constant”
Bernoulli’s law tells us that when a fluid particle decelerates pressure
increases
Bernoulli equation clinical applications
It is used for estimating the severity of an aortic or mitral valve stenosis, arterial stenosis and aneurysms
three components of the cardiovascular system
- Blood is the vehicle for transport
- The circulatory system is the distribution system and consists of a series of branched blood
vessels. - The heart is the four-chambered pump composed mostly of cardiac muscle that enables this circulatory flow
How much time f/ the average RBC to make 1 complete cycle of the body in a typical adult w/ 64 kg of mass?
56 sec
systole lasts for about 1/3 of the cycle, the mean blood pressure is a weighted sum
P mean = (P sys + 2P dias)/3
arterial pulse pressure (P pulse)
difference in pressure of 40 mmHg between systole and diastole
stenotic resistance ___ with flow
stenotic resistance increases with flow
where does much of the pressure drop in the arterial system?
in the arterioles (small arteries) and the capillaries
flow of blood in arteries is affected by (3):
- changes in the heart beat rate
- the volume pumped per beat (stroke volume)
- changes in the arteries themselves that control their diameters by chemical and neural mechanisms
two physical attributes of blood vessels in steady state:
- They have a resistance to flow, and so they need a pressure difference along the length of the vessel to drive the blood flow.
- They have a compliance in response to a distending pressure.
resistance vessel -
rigid vessel with constant volume V
flow rate of the resistance vessel is affected by the pressure drop inside the vessel
Arterioles, capillaries, and venules act like resistance vessels
compliance vessel -
elastic vessel that has no noticeable resistance
volume of the compliance vessel is affected by the pressure difference between the inside and outside of the vessel
aorta, large arteries and large veins are much like compliance vessels
stenosis is quantified by
the ratio As/Ao, called the area ratio
same expression as percentage of error:
(1 - As/A0) * 100
linear term (first term) in the pressure drop-flow equation accounts for
viscous losses within the stenosis
quadratic term (second term) in the pressure drop-flow equation accounts for
losses due to turbulence
severe stenoses (area occlusion higher than 85%), what losses dominate?
turbulent losses
Law of Laplace relates what?
relates transmural P (diff in P b/w 2 sides of a wall) WITH wall stress
T = ΔP * R
Equation of continuity:
statement of the conservation of mass during flow
When a fluid of a given density ρ, moves with average speed v, in a tube of cross-sectional area A, the product ρAv is constant.
Q = A1v1 = A2v2
BERNOULLI’S EQUATION
relates blood pressure (P), and blood flow velocity (v); E law; EXPRESSES THE CONSERVATION OF E IN THE FLOWING BLOOD
v HIGH - P low
LAW OF POISEUILLE
describes the relation between pressure drop, ΔP, and fluid flow, Q, under steady flow conditions
Q = 𝚫𝐏𝝅𝒓𝒊 / 𝟖𝜼𝒍
