Transcript Introduction to Physiology: The Cell and General Physiology

Components of the Circulation
.
Figure 14-1;
Guyton and Hall
Copyright © 2006 by Elsevier, Inc.
The Capillaries Have the Largest Total
Cross-sectional Area of the Circulation
cm2
Aorta
Small Arteries
Arterioles
Capillaries
Venules
Small Veins
Venae Cavae
Copyright © 2006 by Elsevier, Inc.
2.5
20
40
2500
250
80
8
Velocity of Blood Flow is
Greatest in the Aorta
Velocity of Blood Flow =
Blood Flow
Cross sectional area
Aorta >Arterioles> Small veins >Capillaries
Copyright © 2006 by Elsevier, Inc.
The Majority of Blood Volume
is in the Veins
.
Copyright © 2006 by Elsevier, Inc.
Figure 14-1;
Guyton and Hall
Blood Pressure Profile
in the Circulatory System
Pulmonary viens
Capillaries
Large viens
40
Small viens
60
Venules
80
Capillaries
Pressure
(mmHg)
100
Pulmonary arteries
120
20
0
Systemic
Pulmonary
• High pressures in the arterial tree
• Low pressures in the venous side of the circulation
• Large pressure drop across the arteriolar-capillary junction
Copyright © 2006 by Elsevier, Inc.
Variations in Tissue Blood Flow
Brain
Heart
Bronchi
Kidneys
Liver
Portal
Arterial
Muscle (inactive state)
Bone
Skin (cool weather)
Thyroid gland
Adrenal glands
Other tissues
Total
Copyright © 2006 by Elsevier, Inc.
Percent
14
4
2
22
27
(21)
(6)
15
5
6
1
0.5
3.5
100.0
ml/min
700
200
100
1100
1350
(1050)
(300)
750
250
300
50
25
175
5000
Characteristics of Blood Flow
– When laminar flow occurs, the velocity of blood in
the center of the vessel is greater than that toward
the outer edge creating a parabolic profile.
Laminar flow
Copyright © 2006 by Elsevier, Inc.
Blood Vessel
Laminar Vs.
Turbulent Blood Flow
Turbulent flow
• Laminar flow is silent, whereas turbulent flow tend to cause murmurs.
• Murmurs or bruits are important in diagnosing vessels stenosis, vessel
shunts, and cardiac valvular lesions.
Copyright © 2006 by Elsevier, Inc.
Effect of Wall Stress on Blood Vessels
Turbulent flow increases wall stress
Copyright © 2006 by Elsevier, Inc.
Parallel and Serial Resistance
Sites in the Circulation
Copyright © 2006 by Elsevier, Inc.
Effect of Vessel Diameter on
Blood Flow
• Conductance is very sensitive to change in diameter of vessel.
• The conductance of a vessel increases in proportion to
the fourth power of the radius.
Copyright © 2006 by Elsevier, Inc.
Figure 14-9;
Guyton and Hall
Determinants of Blood Flow
FLOW = arterial - venous pressure (P)
resistance (R)
100 mmHg
100 mmHg
A
0 mmHg
R = .1mmHg/ml/min
B
20 mmHg
R = .1mmHg/ml/min
FLOW = 100 - 0 mmHg
.1 mmHg/ml/min
FLOW = 100 - 20 mmHg
.1 mmHg/ml/min
FLOW = 1000 ml/min
FLOW = 800 ml/min
Copyright © 2006 by Elsevier, Inc.
How Would a Decrease in Vascular
Resistance Affect Blood Flow?
FLOW =
P
RESISTANCE
Conversely,
FLOW =
Copyright © 2006 by Elsevier, Inc.
P
RESISTANCE
Hematocrit and Viscosity
Effects on Blood Flow
Figure 14-11; Guyton and Hall
Copyright © 2006 by Elsevier, Inc.
Figure 14-12; Guyton and Hall
Arterial Pulsations
• The height of the pressure pulse is the systolic
pressure (120mmHg), while the lowest point is
the diastolic pressure (80mmHg).
• The difference between systolic and diastolic
pressure is called the pulse pressure
(40mmHg).
Systolic Pressure
}
Pulse Pressure
Diastolic Pressure
Copyright © 2006 by Elsevier, Inc.
Damping of Pulse Pressures
in the Peripheral Arteries
Figure 15-6; Guyton and Hall
Copyright © 2006 by Elsevier, Inc.
Arterial Pulse
Cardiac
output
Systolic Pressure
}
Pulse Pressure
Pressure
Mean
Pressure
Peripheral
resistance
Diastolic
Pressure
Arterial
compliance
Time
Copyright © 2006 by Elsevier, Inc.
Stroke
volume
Abnormal Pressure Pulse
Contours
Figure 15-4; Guyton and Hall
Copyright © 2006 by Elsevier, Inc.
Pulse Pressure and Age
Figure 15-8; Guyton and Hall
Copyright © 2006 by Elsevier, Inc.
Effect of Cuff Pressure on
Brachial Blood Flow
Cuff Pressure > 120
NO FLOW
Cuff Pressure < 80
FREE FLOW
Copyright © 2006 by Elsevier, Inc.
Measurement of Blood Pressure
Use of Korotkoff Sounds
120
100
80
150
100
50
Copyright © 2006 by Elsevier, Inc.
0