Transcript Chapter 19 - Trimble County Schools

PowerPoint® Lecture Slides
prepared by Vince Austin,
Bluegrass Technical
and Community College
CHAPTER
Elaine N. Marieb
Katja Hoehn
19
PART A
Human
Anatomy
& Physiology
SEVENTH EDITION
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
The
Cardiovascular
System: Blood
Vessels
Blood Vessels

Circulatory System is considered a
closed system

Major vessels are arteries, capillaries,
and veins
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Generalized Structure of Blood Vessels

1.
2.
Arteries and veins are composed of three tunics
tunica intima – internal most layer
tunica media – middle layer
Vasoconstriction – reduce lumen size
Vasodilation – increase lumen size
3.
tunica externa
Lumen – central blood-containing space
surrounded by tunics
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Generalized Structure of Blood Vessels
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Figure 19.1b
Vascular Components
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Figure 19.2a, b
Continuous Capillaries

Continuous capillaries are
abundant in the skin and muscles
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Continuous Capillaries

Continuous capillaries of the
brain:

Constitute the blood-brain
barrier
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Fenestrated Capillaries
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Figure 19.3b
Venous System: Venules

Venules are formed when capillary beds unite



Allow fluids and WBCs to pass from the
bloodstream to tissues
Postcapillary venules – smallest venules,
composed of endothelium and a few pericytes
Large venules have one or two layers of smooth
muscle (tunica media)
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Venous System: Veins

Lower blood pressure

Large-diameter lumen

Valves


Venous sinuses – specialized, flattened veins with
extremely thin walls (e.g., coronary sinus of the
heart and dural sinuses of the brain)
65% of body blood supply is found in the veins –
capacitance vessels
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Vascular Anastomoses

Alternate pathways to body area if
a branch is blocked
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Blood Flow, Blood Pressure, and Resistance

Blood flow (F) is directly proportional to the
difference in blood pressure (P) between two
points in the circulation


Blood flow is inversely proportional to resistance
(R)


If P increases, blood flow speeds up; if P
decreases, blood flow declines
If R increases, blood flow decreases
R is more important than P in influencing local
blood pressure
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Flow, Pressure and Resistance
1.
2.
3.
Blood flow – the volume of blood flowing
through a vessel
Pressure – force per unit area exerted against a
vessel containing blood (mm Hg.)
Resistance – opposition to flow as the blood
passes through the vessels (viscosity, length and
diameter)
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Systemic Blood Pressure
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Figure 19.5
Arterial Blood Pressure





Systolic pressure – pressure exerted on arterial
walls during ventricular contraction
Diastolic pressure – lowest level of arterial
pressure during a ventricular cycle
Pulse pressure – the difference between systolic
and diastolic pressure
Mean arterial pressure (MAP) – pressure that
propels the blood to the tissues
MAP = diastolic pressure + 1/3 pulse pressure
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Factors Aiding Venous Return


Venous BP alone is too low to promote
adequate blood return and is aided by the:

Respiratory “pump”

Muscular “pump”
Valves prevent backflow during venous
return
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Factors Aiding Venous Return
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Figure 19.6
Short-Term Mechanisms


Vasomotor center – medulla
detects changes in the size of
lumen
Cardiovascular - alters cardiac
output and blood vessel
diameter
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Short-Term Mechanisms: Chemical Controls

Oxygen and carbon dioxide

Aortic and carotid areas
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Kidney Action and Blood Pressure

Kidneys act directly and indirectly to
maintain long-term blood pressure
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Palpated Pulse
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Figure 19.11
Measuring Blood Pressure

Systemic arterial BP is measured indirectly with
the auscultatory method

A sphygmomanometer is placed on the arm
superior to the elbow

Pressure is increased in the cuff until it is greater
than systolic pressure in the brachial artery

Pressure is released slowly and the examiner
listens with a stethoscope
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Measuring Blood Pressure

The first sound heard is recorded as the systolic
pressure

The pressure when sound disappears is recorded as
the diastolic pressure
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Alterations in Blood Pressure


Hypotension – low BP in which
systolic pressure is below 100 mm
Hg
Hypertension – condition of
sustained elevated arterial pressure
of 140/90 or higher
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