cardiovascular physiology 4 - gomez md.pdf

8/12/2019 Cardiovascular Physiology 4 - Gomez MD.pdf

1/65


2/65

BLOOD VESSELS

VEINS

ARTERIES

CAPILLARIES

PULMONARY CIRCULATION

SYSTEMIC CIRCULATION


3/65


4/65

Marieb, Human Anatomy and Physiology, 7thedition


5/65

ARTERIES

transport blood

under high pressure

high velocity flow 8x less distensible

than veins

transport blood awayfrom the heart

carry oxygenated

blood


6/65

TYPES OF ARTERIES

ELASTIC ARTERIES

(LARGE-SIZED)

MUSCULAR ARTERIES

(MEDIUM-SIZED)

RESISTANCE ARTERIES

(SMALL-SIZED)


7/65

ELASTIC ARTERIES

a.k.a. large-sized

arteries or conducting

arteries

elastic tissue and

smooth muscle

pulsatile flow pressure fluctuations


8/65

MUSCULAR ARTERIES

a.k.a. medium-sized

arteries or distributing

arteries

(+) elastic tissue and

smooth muscle

pulsatile flow


9/65

RESISTANCE ARTERIES

a.k.a. small-sized

arteries

elastic tissue and

smooth muscle

pulsatile flow

stopcocks (controlconduits) of the

vascular system


10/65

CAPILLARIES Made up of single layer of

endothelial cells and

basement membrane

(-) smooth muscle and (-)

elastic tissue

Contain tight junctions,

fenestrations (pores),

intercellular cleft and and

pericytes

Total area exceeds 6300 m2and

1 m thick


11/65

CONTINUOUS CAPILLARIES

FENESTRATED CAPILLARIES

SINUSOIDAL CAPILLARIES

TYPES OF CAPILLARIES


12/65


13/65

Hydraulic conductivity of capillaries in

various parts of the body(Ganong, Medical Physiology 2001)

Organ Conductivity Type of Endothelium

Brain (except CVO) 3

Skin 100Skeletal muscle 250 Continuous

Lungs 340

Heart 860

GIT (intestinal mucosae) 13,000 Fenestrated

Kidney (glomerulus)

Liver

Bone marrow

Endocrine glands Sinusoidal

Lymphoid tissue

(Marieb, Human Anatomy and Physiology)


14/65

VEINS

Transport blood

under low pressure.

8x more distensiblethan arteries

transport blood

towards the heart

carry deoxygenated

blood.

Great veins no valves, thin and easily

distended

Venules no valves, walls slightly

thicker than capillaries


15/65


16/65

Basic Theory of Circulatory Function Rate of blood flow to each tissues is

almost always precisely controlled in

relation to the tissue needs. The cardiac output is controlled mainly

by the sum of all the local tissue flows.

In general, the arterial blood pressure iscontrolled independently of either local

blood flow control of cardiac output

control


17/65

Structural and Functional Differences of Various

Blood Vessels

Lumen Diameter and Wall Thickness

Vessel Lumen Diameter Wall Thickness

Aorta 2.5 cm 2 mm

Medium-sized 0.4 cm 1 mm

Arteriole 30.0 m 20 m

Capillary 5.0 m 1 m

Venule 20.0 m 2 m

Vein 0.5 cm 0.5 mm

Great vein 3.0 cm 1.5 mm


18/65

Vessel % of blood

volume

Systemic 84 %

Arteries 13 %

Arteriole 1-2 %

Capillary 5 %

Veins 64 %(54 %)

Pulmonary/Heart 16 %

Lungs 9 %

Heart 7 %

BLOOD DISTRIBUTION


19/65


20/65

Total Cross Sectional Area

Vessel Areas (cm2)

aorta 2.5

medium-sized 20.0arterioles 40.0

capillaries 2500.0

venules 250.0veins 80.0

great veins 8.0


21/65

Pressure


22/65


23/65

Blood Flow Velocity


24/65

Resistance to Blood Flow


25/65

Vascular Distensibility

1 ml= ----------------------------

1mmHg X 10 ml

= 0.1 per mmHg or 10 mmHg

Systemic and pulmonary circulationdistensibility

Veins > Arteries

Vein DistensibilitySystemic veins = Pulmonary veins

Arterial DistensibilityPulmonary > Systemic


26/65

Vascular Compliance / Capacitance

Vascular Compliance = Distensibility X Volume

Guyton, Medical Physiology, 11thedition


27/65


28/65

HEMODYNAMICS

study of physical properties that

govern blood flow through the blood

vessels and the heart.


29/65

BLOOD FLOW

means the quantity

of blood that passes a

given point in thecirculation in a given

period of time.

usually expressed in

ml/min or L/min

(cm3/min).


30/65


31/65

BLOOD FLOW

( P1 - P2)F = ------------------

R

where,

F = flow

P1

P2 = pressure difference or gradient ofblood between two points of the vesselR = resistance to flow ( vascular

resistance)

pressure differencebetween two ends of

the vessel (arterialend minus venous

end)

impediment to bloodflow in a vessel.

cannot be measureddirectly

expressed in R units

The overall blood flow in

the total circulation in a

resting adult is 5,000 ml.(Cardiac Output)


32/65


33/65

Methods for measuring blood flow

(Flowmeters) Electromagnetic Flowmeters

Ultrasonic Doppler Flowmeters

Fick Principle

Indicator Dilution Method

Clearance Principle

Plethysmography


34/65


35/65

POISEUILLES EQUATION

P . r4

F -----------------

. Lwhere,

F = flow

P = pressure difference between

two ends of the vessel = viscosityr4 = radius

L = length of the tube


36/65

Since flow (F) is equal to pressure

difference (P) divided by resistance (R)

. LR ------------

r4


37/65

Determinants of vascular resistance Radius of the blood vessel

depends on the degree of vasoconstriction

Viscosity of the blood depends mainly on hematocrit (% of volume

of blood occupied by the RBC

amount of protein in the blood

Hyperimmunoglobulin D, E and M resistance of the cell to deformation

(Hereditary Spherocytosis)

Length of the blood vessel


38/65

EFFECT OF CHANGES IN BLOOD VESSEL RADIUS


39/65

EFFECT OF CHANGES IN BLOOD VESSEL LENGTH


40/65


41/65

Shear Stress and Shear rate

Shear Stress

Force created by flowing blood on the

endothelium that is parallel to the long axisof the vessel

Equal to viscosity X shear rate

Shear rate Rate at which axial velocity from the vessel

wall towards the lumen


42/65

Resistance in Series vs Resistance in Parallel


43/65


44/65

CONDUCTANCE

Measure of blood

flow through avessel for a given

pressure difference

1

C = --------------------------

RESISTANCE


45/65

F

F = V . A or V = ------

A

where;

F = flowV = mean velocity

A = cross-sectional area of the blood vessel

FLOW, VELOCITY AND AREA


46/65

BERNOULLIS PRINCIPLE


47/65


48/65

Laminar vs. Turbulent F low

Laminar flow (Streamline flow)

silent flow

characterized by concentric layer of blood moving inparallel down the length of a blood vessel.

Turbulent flow

flow that that creates sound

probability is also related to the diameter of thevessel and viscosity of the blood

can be expressed by


49/65


50/65

Conditions that can result to

turbulent flowa) When blood flow becomes too great.

b) When there is obstruction in a vesselc) When it makes a sharp turn.

d) When it passes over a rough surface

Turbulent flow in proximal aorta and

pulmonary arterya) High velocity of blood flow

b) Pulsatile nature of blood flowc) Sudden change in vessel diameter

d) Large vessel diameter


51/65

p . D . V

Re = ----------------

where,

Re = Reynolds number

p = density of the fluid

D = diameter of the tubeV = velocity of flow

= viscosity of the fluid


52/65

LAW OF LAPLACE

T = Pr


53/65

BLOOD PRESSURE force exerted by the

blood per unit area of

the vessel wall(pressure is exerted

equally in all

directions).


54/65

Blood Pressure in the Various

Parts of the Systemic Circulation

Mean Blood Pressure

average pressure in any segment of the

cardiovascular system during cardiac cycle.

Arterial Blood Pressure

blood pressure in the arterial side of the vascular

system conveniently written as systolic pressureover diastolic pressure ( N.V. 100 -130 / 70 -

90 mmHg )


55/65


Systolic pressure

highest pressure attained in the aorta as a result of the

ejection of blood by the ventricle.(N.V. 100 - 120 mmHg )

Diastolic pressure

is the lowest pressure which the gradient of fall reachesduring the resting or diastolic phase of the heart.

( 70 - 80 mmHg)


56/65

Pulse Pressure

is the difference between the systolic and

diastolic pressure. (SPDP = 40 mmHg)

factors that affect pulse pressure (SV/C) Stroke volume

Compliance of arterial tree


57/65

Mean Arterial Blood Pressure represents the average pressure attained inthe arterial system during the cardiac cycle.

MAP = Diastolic Pressure + 1/3 pulse pressure

Diastolic Pressure + ( Systolic Diastolic pressure )

MAP= -----------------------------------------

3


58/65


ABP = CO X TPR

CO ABPTPR ABP

CO = SV X HR

EDV - ESV


59/65

ABP = CO X TPR

SV X HR

EDV - ESV


60/65

RESISTANCE

. LR ------------

r4

a) viscosity hematocrit

amount of protein in the blood

b) lengthc) radius

vasoconstriction /vasodilatation


61/65

EDVSV CO ABP ESV

Blood viscosity

Vessel length TPR ABP

Vessel radius


62/65

Methods of Measuring Blood PressureA. Direct Method

B. Indirect Method

a) Auscultatory Methodb) Palpatory Method

increased pressure ----------- HYPERTENSION

decreased pressure ----------- HYPOTENSION


63/65


64/65


65/65

cardiovascular physiology 4 - gomez md.pdf

Documents