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Chapter 21
Blood Vessels and Circulation - pp. 721-740
I. The Anatomy of Blood Vessels - Figs. 21.1-21.7
A. Differences between arteries and veins - Fig. 21.1
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Compared to veins, arteries
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Have thicker walls
Have more smooth muscle and elastic fibers
Are more resilient
B. Arteries/Arterioles
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Undergo changes in diameter
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Vasoconstriction – decreases the size of the lumen
Vasodilation – increases the size of the lumen
Classified as either elastic (conducting) or muscular (distribution)
Small arteries (internal diameter of 30 um or less) are called arterioles
C. Capillaries - Fig. 21.4, 21.5
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An endothelial tube inside a basal lamina
These vessels
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Form networks
Surround muscle fibers
Radiate through connective tissue
Weave throughout active tissues
Capillaries have two basic structures
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Continuous
Fenestrated
D. Veins - Fig. 21.6
• Collect blood from all tissues and organs and return it to the heart
• Are classified according to size
• Venules
• Medium-sized veins
• Large veins
• Venules and medium-sized veins contain valves
• Prevent backflow of blood
II. Cardiovascular Physiology
A. Circulatory Pressure - Fig. 21.8
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Circulatory pressure is divided into three components
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Blood pressure (BP)
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Capillary hydrostatic pressure (CHP)
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Venous pressure
B. Resistance (R)
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Resistance of the cardiovascular system opposes the movement of blood
For blood to flow, the pressure gradient must overcome total peripheral resistance
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Peripheral resistance (PR) is the resistance of the arterial system
C. Overview of Cardiovascular Pressures - Fig. 21.9
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Factors involved in cardiovascular pressures include
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Vessel diameter
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Cross-sectional area of vessels
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Blood pressure
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Blood viscosity
D. Arterial blood pressure - Fig. 21.10
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Arterial blood pressure
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Maintains blood flow through capillary beds
Rises during ventricular systole and falls during ventricular diastole
Pulse is a rhythmic pressure oscillation that accompanies each heartbeat
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Pulse pressure = difference between systolic and diastolic pressures
Mean arterial pressure (MAP)
E. Capillary Exchange
• Flow of water and solutes from capillaries to interstitial space
• Plasma and interstitial fluid are in constant communication
• Assists in the transport of lipids and tissue proteins
• Accelerates the distribution of nutrients
• Carries toxins and other chemical stimuli to lymphoid tissues
1) Processes that move fluids across capillary walls - Fig. 21.12
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Diffusion
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Filtration
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Hydrostatic pressure (CHP)
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Reabsorption
2) Forces acting across capillary walls - Fig. 21.13
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Capillary hydrostatic pressure (CHP)
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Blood colloid osmotic pressure (BCOP)
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Interstitial fluid colloid osmotic pressure (ICOP)
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Interstitial fluid hydrostatic pressure (IHP)
3) Filtration and reabsorption
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Processes involved in filtration and reabsorption include
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Net hydrostatic pressure
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Net colloid osmotic pressure
• CHP - IHP
• BCOP - ICOP
F. Venous pressure and venous return
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Assisted by two processes
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Muscular compression
The respiratory pump