Summary Guyton and Hall Chapter 15 Notes - Vascular Distensibility and Functions of the Arterial and Venous Systems
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Physiology (PHYSIOLOGY)
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Cebu Doctor\'s University
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Guyton and Hall Textbook of Medical Physiology
This is a condensed summary of the Chapter 15 - Vascular Distensibility and Functions of the Arterial and Venous Systems from Guyton and Hall Textbook of Medical Physiology 14 Ed. It contains pictures from the book as well. Use these notes to study for your upcoming exam or quiz.
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Guyton and Hall Textbook of Medical Physiology 14th Edition Test Bank by John E. Hall, Michael E. Hall
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CHAPTER 15 When the arterial system of the average adult person is filled
with about 700 mL of blood, the mean arterial pressure is
VASCULAR DISTENSIBILITY AND FUNCTIONS OF THE 100 mmHg, but when it is filled with only 400 mL of blood,
ARTERIAL AND VENOUS SYSTEMS the pressure falls to 0.
2,000 to 3,500 mL is the normal volume range in the entire
VASCULAR DISTENSIBILITY systemic venous system. A change of several hundred in this
volume is required to change the venous pressure by only 3-
Distensible – capable of being extended or dilated 5 mmHg. This explains why as much as 0.5L of blood can be
transfused into a healthy person in only a few minutes
All blood vessels are distensible, which allows: without greatly altering the function of the circulation.
The arteries to accommodate the pulsatile output of An increase in vascular smooth muscle tone caused by
the heart to average out the pressure pulsations sympathetic stimulation increases the pressure at each
Provide smooth continuous blood flow of blood volume of the arteries or veins, and v.v.
through the very small blood vessels of the tissues
Control of the vessels by the sympathetic system is a
The veins are the most distensible of all the vessels valuable means for diminishing the dimensions of one
segment, transferring blood to other segments. Ex: an
- Even a slight increase in venous pressure cause increase in vascular tone throughout the systemic circulation
the veins to store 0.5 to 1 liter of extra blood can cause large volumes of blood to shift to the heart, which
- The veins provide a reservoir for storing large is one of the principal methods that the body uses to rapidly
quantities of extra blood increase heart pumping
- This reservoir can be called to use whenever blood
is required elsewhere in the circulation Sympathetic control of vascular capacitance is also highly
important during hemorrhage, because it can reduce the
Vascular distensibility is expressed as the fractional increase vessel sizes enough that the circulation continues to operate
in volume for each mm Hg rise in pressure: almost normally, even when as much as 25% of the total
𝑖𝑛𝑐𝑟𝑒𝑎𝑠𝑒 𝑖𝑛 𝑣𝑜𝑙𝑢𝑚𝑒 blood volume has been lost.
𝑉𝑎𝑠𝑐𝑢𝑙𝑎𝑟 𝑑𝑖𝑠𝑡𝑒𝑛𝑠𝑖𝑏𝑖𝑙𝑖𝑡𝑦 =
𝑖𝑛𝑐 𝑖𝑛 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑥 𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑣𝑜𝑙𝑢𝑚𝑒 Delayed compliance – means that a vessel exposed to
increased volume at first exhibits a large increase in
Meaning if 1 mm Hg causes a vessel originally containing 10
pressure, but progressive delayed stretching of smooth
mL of blood to increase its volume to 11 mL or by 1 mL, the
muscle in the vessel wall allows the pressure to return
distensibility would be 0.1 per mm Hg or 10% per mm Hg.
toward normal over a period of minutes to hours.
The walls of the arteries are thicker and far stronger than
- Stress-relaxation – when the smooth muscle fibers
those of the veins, and so the veins are more distensible
of the vein stretches and helps in decreasing
(about 8x more) than the arteries.
tension of the distended veins during blood vessels
For veins, pulmonary vein distensibilities are similar to those exposure to increase in volume and increase in
of the systemic vein distensibilities. pressure.
- Delayed compliance is a valuable mechanism
For arteries, pulmonary artery distensibilities are about 6x whereby the circulation can accommodate extra
greater than those of the systemic artery distensibilities. This blood when necessary
is due to the less pressure in the pulmonary arteries. - Delayed compliance in the reverse direction is one
way in which the circulation automatically adjusts
Vascular capacitance or compliance – the total quantity of itself over a period of minutes or hours to
blood that can be stored in a given portion of the circulation diminished blood volume after serious hemorrhage.
for each mm Hg pressure rise
𝐶𝑜𝑚𝑝𝑙𝑖𝑎𝑛𝑐𝑒 = 𝑑𝑖𝑠𝑡𝑒𝑛𝑠𝑖𝑏𝑖𝑙𝑖𝑡𝑦 𝑥 𝑣𝑜𝑙𝑢𝑚𝑒 The compliance of the arterial tree normally reduces the
pressure pulsations to
A highly distensible vessel that has a small volume may have almost no pulsations by
far less compliance than a much less distensible vessel that the time the blood
has a large volume. reaches the capillaries
The compliance of a systemic vein is about 24x that of its Meaning, tissue blood
corresponding artery because it is about 8x as distensible flow is mainly continuous
and has a volume about 3x as great. with very little pulsation
VOLUME-PRESSURE CURVES OF THE ARTERIAL AND Pressure pulsations at the
VENOUS CIRCULATIONS root of the aorta
Volume-pressure curve is Pulse pressure – difference between the systolic pressure
used to express the (120 mmHg) and diastolic pressure (80 mmHg). 2 major
relationship of pressure to affecting factors:
volume in a vessel or in any
portion of the circulation. 1. Stroke volume output of the heart
2. Compliance (total distensibility) of the arterial tree
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