Haemodynamics Nov2 M2

Question 1

Average number of cells for a capillary and reason

Answer 1

1 capillary for every cell on avg -> large number of capillaries surrounding cell = are very close to all parts of the cell = large flow in cell

Question 2

Qualitative definition of diffusion

Answer 2

Spontaneous movement of particles caused by random thermal motion

Question 3

Definition (in words) for flux and for flow that don’t come from prof (for understanding)

Answer 3

Flux = Rate of volume flow across a unit area (per second) in m3/sm2. Flow = Volume of fluid which passes in some area(per second) in m3/s.

Question 4

Prof definition/formula for flux and units for flow

Answer 4

Flux = Flow/Area = D x concentration gradient. Flow is in mol/s

Question 5

Meaning of a concentration gradient and of D in flux formula + complete formula

Answer 5

Concentration gradient = (Cout- Cin)/d must divide by the distance D = diffusion coefficientFlux (mol/s for prof) = D x(Cout- Cin)/d

Question 6

Flow formula in terms for flux and complete

Answer 6

Flow = flux x area. Flow = D x(Cout- Cin)/d x A

Question 7

How much oxygen a person uses every minute + What principle rules the movement of air from outside of our airways to our alveoli

Answer 7

200-250 mL of oxygen/minute = what we use. Bulk flow responsible formovement of air to our alveoli (and not diffusion)

Question 8

Other name for bulk flow and 4 steps to get outside air to our cells

Answer 8

Convective flow. Convection from the outside to the alveoli -> Diffusion to the capillaries -> Convection from lung capillaries to tissue capillaries -> Diffusion from blood to tissue

Question 9

All transportwithinthe cardiovascular system OR the respiratory system is done through _________________. ll transportbetweenhe cardiovascular system AND the respiratory system is done through _________________

Answer 9

convection, diffusion

Question 10

Haemodynamics definition and 4 concepts to understand it

Answer 10

Volume, Flow, Pressure, Resistance

Question 11

Avg blood volume, def. of 1 unit of blood, characteristics of the reference individual

Answer 11

5L blood in body. 1 unit of blood = 450 mL (amount at donation). Ref. individual = 70 kg young healthy male lying flat on his back.

Question 12

Blood distribution in the body when lying flat

Answer 12

60% in vein/venules, 10% in arteries, 10% in capillaries, 10% in heart, 10% in lungs

Question 13

Other name for the venous system and other name for its vessels and why

Answer 13

Capacitance system and capacitance vessels. Because most blood in venous system when lying flat (has a capacity to hold stuff)

Question 14

Other name for the arterial system and why

Answer 14

Resistance system because resistance to flow of blood from ventricles is mainly in the arterioles and small arteries

Question 15

Flow output from the left/right heart : Name and value

Answer 15

Cardiac output. 5000 mL/min

Question 16

Name and value for the flow that goes from the lungs to the left heart and for the flow that goes from the organs to the right heart. Reason for this value

Answer 16

Venous return. 5000 mL/min. Must be same as cardiac output because of conservation of mass

Question 17

Method for flow measurement and conventional physiology units

Answer 17

Pump blood or fluid through a vessel that is not in the body. Collect volume that exits vessel (V) and record time (T). Flow = V/T. In mL/min or L/min.

Question 18

How do we compare the flow for different organs

Answer 18

You normalize per unit of mass and so flow is calculated in mL/min/100g

Question 19

What influences the flow (2). Give units and how these units give the units of flow

Answer 19

Cross-sectional area or flow velocity (flux). F = area x velocity = A x v. Certain volume moving through a tube at 1 cm/sx A gives you the volume of the cylinder of blood that travelled in 1 sec in cm3/s.1 cm3(1 cc - cubic centimeter) = 1 mL

Question 20

Formula of flow is F = A x v. Small correction that must be done and why

Answer 20

F = area x mean velocity because not all blood travels at the same velocity at all points in a cross section

Question 21

How vessels chance as they get further from the heart ? And when they get closer to the heart ? Name for this pattern

Answer 21

Increase in number, become smaller in diameter and shorter in length. Opposite when getting closer to heart (less numerous, larger diameter, longer in length). Pattern = Vascular tree

Question 22

Kind/categories of vessels in the vascular tree starting from the left ventricle and note about branching

Answer 22

Aorta, arteries, arterioles, capillaries, venules, veins, vena cava (sup and inf). There is branching within each category (arteries -> smaller arteries -> smallest arteries before arterioles)

Question 23

Why is there a very complex arterial branching in the kidneys

Answer 23

To facilitate diffusion. A shorter distance for O2 (all cells near a capillary) = greater gradient

Question 24

How total cross-sectional area varies as we go down in levels of branching and how total flow varies with each level of branching ? How do we calculate these

Answer 24

Total cross sectional area increases (add up all vessels’ cross sectional area in one level of branching = total cross-sectional area). Total flow at each level of branching is the same. Add flow from each vessel of one level of branching = total flow

Question 25

What can be deduced if flow is the same in all levels of vascular tree but cross-sectional area increases.

Answer 25

F = v x A. Mean velocity decreases with level of branching -> By the time blood gets to capillaries, it moves very slowly

Question 26

Other advantage of a high total cross sectional area

Answer 26

Total blood vessel wall area increases. More surface area for gas/molecule diffusion to take place

Question 27

Advantage of low flow velocity (in the capillaries for ex)

Answer 27

Allow time for gas/molecules to diffuse through capillary membrane. If RBC went fast through capillary, they wouldn’t have time

Question 28

Summary of 3 advantages (and explanation) for a branching network like the vascular tree

Answer 28

1. High total cross-sectional area (less resistance, less effort from the heart, smaller heart) 2. High total surface area (greater diffusion area) 3. Low flow velocity (more time to allow diffusion)

Question 29

Definition of pressure (formula) and 3 units (SI + 2 practical units)

Answer 29

Pressure = Force/Area. S.I : Pascal (Pa) = newton/m2Practical units : cm H2O or mmHg

Question 30

Pressure units used for arterial BP and venous BP. and normal values

Answer 30

BP in arteries : use mmHg (normal BP is 120/80 mmHg). BP in veins : use cm H2O (central venous pressure is 5-10 cm H2O)

Question 31

How to have pressure without flow ? Characteristics of the pressure

Answer 31

Yes. Take a bag with saline connected to a tube, plug it, squeeze the bag -> P w/o F. Pressure is uniform and exerted in all directions

Question 32

Bag of saline linked to a tube. How to find flow in one portion of the tube + what happens if this system is closed

Answer 32

Add up the forces acting on the portion. F = PxA from one side and F=PxA from other side. Closed system -> Forces equal in magnitude and opposite in direction (because P same everywhere)-> Net flow of 0.

Question 33

In the pressurized saline bag-tube system, where does the pressure energy come from ? + Proof

Answer 33

Comes from work applied (energy) ofsqueezing the bag -> became pressure energy. Proof : Making a hole in the system would have fluid flow out without any other work necessary

Question 34

What does the heart do that is analogous to the bag-tube saline system

Answer 34

Ventricles pumping pressurize the system and store energy in it, which starts flow

Question 35

Bag-tube saline system : If we open the end of the tube what happens

Answer 35

P inlet (bag/tube fork) > P outlet (where tube open and pressure gradient determines flow direction. Fluid flows out

Question 36

Bag tube saline system : How to find flow in one portion of the tube and what happens if the tube is open

Answer 36

Calculate F=PxA on both side of the section of interest. On the closed side, pressure is greater so force from closed side > force from open side -> flow outwards

Question 37

Bag tube saline system : In perfect world/conditions, how would the fluid move outwards and what happens IRL

Answer 37

The fluid would accelerate (force being applied). IRL, internal friction in the opposite direction due to the viscosity of the fluid keeps the flow rate constant

Question 38

How to determine fluid pressure in middle of the tube + How pressure changes in the tube as fluid flows out ? Why

Answer 38

Mean of Pinlet and Poutlet. Flow out -> Pressure falls in tube due to pressurized energy given up to overcome frictional forces

Question 39

How pressure varies down the vascular tree (aorta vs venae cavae for ex) and what this is helpful for

Answer 39

Falls down. Aorta : 100 mmHg. Venae cavae: 5 mmHg. This fall in pressure keeps the flow at some level

Question 40

Hydrostatic pressure definition, + other simple def. + value in space

Answer 40

Pressure exerted by fluid at equilibrium at any given point within the fluid due to the force of gravity.. i.e. Pressure of fluid when it is not moving. In space, no hydrostatic pressure because no gravity

Question 41

Formula for hydrostatic pressure and derivation from situation of fluid in a standing tube

Answer 41

P = force/area = mass x acceleration / area = density x volume x acceleration / area = density x height x area x accel. / area = (density)(g)(h)

Question 42

How hydrostatic pressure inused for medical practice on Earth + reference point

Answer 42

density and g are disregarded so only use height -> cm of H2O. 1 cm H2O = 0.98 kPa

Question 43

In standing cylinder of 10 cm of water, top pressure, bottom pressure and how to find pressure in middle or any point

Answer 43

Top pressure = 0 cm H2O (but not exactly because there is air around, we’re not in space). Bottom = 10 cm H2O. Middle = 5 cm H2O. Only need to check height of fluid above the point

Question 44

Atmospheric pressure, atm PO2 and meaning of atm P

Answer 44

760 mmHg (101.3 kPa). PO2 atm = 150 mmHg. Atm pressure = pressure of square inch area column of air from earth surface to stratosphere.

Question 45

First measurement of hydrostatic pressure : method used

Answer 45

Tube stuck in coronary artery of horse, blood squirts up until reaches max height. Mark height.

Question 46

In first hydrostatic P measurement experiment, why blood eventually stops moving up the tube + give height of stop and pressure measured

Answer 46

HP at bottom of column eventually equals blood P in the horse. 280 cm observed so approx arterial BP of 280 cm H2O (water density approx = blood density)

Question 47

Conversion of pressure from cm H2O to cm Hg and why these units became popular

Answer 47

1 cm Hg = 14 cm H2O. cm Hg became used because Riva-Rocci invented the mercury sphygmomanometer

Question 48

How to use sphygmomanometer + why wedon’t use it anymore

Answer 48

Wind cuff around arm and pump black rupper connected to reservoir of mercury until mercury height stops changing. Stopped used because Hg is a neurotoxin