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Human Anatomy and
Physiology
Unit IV
Circulation and Body
Defense
Part III
Blood Vessels
Blood Vessel Topics
1.
2.
3.
4.
5.
6.
7.
Components of the blood vessel system
Basic structures of blood vessels
Blood distribution
Capillary exchange
Factors affecting blood pressure and flow
Control of blood pressure and flow
Circulatory routes
Components of the Blood Vessel
System
The circulatory system is composed of
arteries, arterioles, capillaries, venules,
and veins
Components of the Circulatory
System
Veins
Heart
Venules
Arteries
Capillaries
Arterioles
Blood Vessel Topics
1.
2.
3.
4.
5.
6.
7.
Components of the blood vessel system
Basic structures of blood vessels
Blood distribution
Capillary exchange
Factors affecting blood pressure and flow
Control of blood pressure and flow
Circulatory routes
Basic Blood Vessel Structure
Specializations of the blood vessel wall
gives different types of vessels their
unique functions
Basic Blood Vessel Structure
Tunica
Interna
Tunica
Media
Endothelium
Smooth
muscle
Basement
membrane
External
elastic
lamina
Internal
elastic
lamina
Tunica
Externa
Connective
tissue
Figure 21.1Comparative structure of blood vessels
Arteries
Elastic
• Well-defined elastic
laminae
• Thick tunica media
dominated by elastic
fibers
• Act as pressure
reservoirs
Muscular
• Well-defined internal
elastic lamina but thin
external elastic lamina
• Thick tunica media
dominated by smooth
muscle
• Maintain vascular tone
Figure 21.2 Pressure reservoir function of elastic
arteries
Figure 21.2 Pressure reservoir function of elastic
arteries
Elastic Artery
Muscular Artery
Arterioles
•
•
•
•
Poorly defined internal
elastic lamina
Thin layer of smooth
muscle forming
precapillary sphincter
Well-innervated tunica
external
Control blood flow into
capillary beds
Figure 21.3 Arterioles, capillaries, and venule
Figure 21.3 Arterioles, capillaries, and venule
Capillaries
 Microscopic; smallest vessels in body
 Tunica interna: endothelium and basement
membrane
 Tunica media: None
 Tunica externa: None
 Permit exchange of nutrients and wastes
between blood and interstitial fluid;
distribute blood to postcapillary venules
Figure 21.3 Arterioles, capillaries, and venule
Figure 21.1Comparative structure of blood vessels
Types of Capillaries
Three types
1.Continuous – leaky; muscle, CT, lungs
2.Fenestrated – leakier; kidneys, sm. Intestine,
brain, eye, endocrine glands
3.Sinusoids – leakiest; liver, red bone marrow,
spleen
Figure 21.4 Anatomy of a continuous capillary
Figure 21.4 Anatomy of a fenestrated capillary
Figure 21.4 Anatomy of a sinusoidal capillary
Figure 21.3 Arterioles, capillaries, and venule
Venules
 Microscopic
 Tunica interna: endothelium and basement
membrane
 Tunica media: 1-2 layers of smooth muscle
 Tunica externa: Sparse
 Pass blood into veins; act as blood
reservoirs
Figure 21.3 Arterioles, capillaries, and venule
Veins
 Range from 0.5mm-30mm
 Tunica interna: endothelium and basement
membrane; no internal elastic lamina;
contains valves; large lumen
 Tunica media: Much thinner than in
arteries; no external elastic lamina
 Tunica externa: Thickest of three layers
 Return blood to heart
Figure 21.5 Venous veins
Blood Vessel Topics
1.
2.
3.
4.
5.
6.
7.
Components of the blood vessel system
Basic structures of blood vessels
Blood distribution
Capillary exchange
Factors affecting blood pressure and flow
Control of blood pressure and flow
Circulatory routes
Blood Distribution
Because systemic veins and venules
contain more than half the total blood
volume, they are called blood reservoirs
Figure 21.6 Blood distribution in the
cardiovascular system
Blood Vessel Topics
1.
2.
3.
4.
5.
6.
7.
Components of the blood vessel system
Basic structures of blood vessels
Blood distribution
Capillary exchange
Factors affecting blood pressure and flow
Control of blood pressure and flow
Circulatory routes
Capillary Exchange
Blood hydrostatic pressure pushes fluid
out of capillaries (filtration), and blood
colloid osmotic pressure pulls fluid into
the capillaries (reabsorption)
Figure 21.7 Capillary exchange
Blood Vessel Topics
1.
2.
3.
4.
5.
6.
7.
Components of the blood vessel system
Basic structures of blood vessels
Blood distribution
Capillary exchange
Factors affecting blood pressure and flow
Control of blood pressure and flow
Circulatory routes
Blood Flow
 BF= CO; (SV X HR)
 The same factors that change CO
change BF
 Stroke volume: preload and
contractility
 Heart rate: nervous system and
chemicals
Figure 21.8
Figure 21.9
Figure 21.10
Figure 21.11