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Human Anatomy and Physiology Unit IV Circulation and Body Defense Part III Blood Vessels
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Blood Vessel Topics 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
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Components of the Blood Vessel System
The circulatory system is composed of: Arteries Arterioles Capillaries Venules Veins
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Components of the Circulatory System
Heart Arteries Arterioles Capillaries Venules Veins
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Circulatory System Systemic Circulation Pulmonary Circulation
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Blood Vessel Topics 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
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Basic Blood Vessel Structure
Specializations of the blood vessel wall gives different types of vessels their unique functions.
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Basic Blood Vessel Structure
Tunica Interna Endothelium Basement membrane Internal elastic lamina Tunica Media Smooth muscle External elastic lamina Tunica Externa Connective tissue
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Figure 21.1 Comparative structure of blood vessels
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Arteries Arterial Tunica Interna Arterial Tunica Media
Internal elastic lamina Strength Elasticity Arterial Tunica Media Elastic Fibers Compliance Thick smooth muscle Vasoconstriction Vasodilation External elastic lamina Arterial Tunica Externa Thick and protective
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Arteries Functional Properties Elasticity Contractility
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Arteries Elastic Muscular 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
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Figure 21.2 Pressure reservoir function of elastic arteries
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Elastic Artery
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Muscular Artery
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Figure 21.1 Comparative structure of blood vessels
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Anastomoses Collateral circulation End arteries Occlusion = necrosis
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Arterioles Almost microscopic Control blood flow into capillary beds
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Arterioles Arteriolar Tunica Interna Arteriolar Tunica Media
Poorly defined internal elastic lamina Arteriolar Tunica Media Thin layer of smooth muscle Precapillary sphincter Arteriolar Tunica Externa Well innervated for good control of BF
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Arterioles Figure 21.3 Arterioles, capillaries, and venules
Metarteriole Precapillary sphincter Resistance vessels Figure Arterioles, capillaries, and venules
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Figure 21.3 Arterioles, capillaries, and venules
Decrease blood flow by contracting sphincters = closing taps = limit blood flow Control blood flow to a tissue as need be
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Capillaries Microscopic; smallest vessels in body
Arterial outflow venous return Microcirculation Metarteriole capillaries postcapillary venules Distribution varies with metabolic activity of tissues. Exchange vessels
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Capillaries Capillary Tunica Interna Capillary Tunica Media
Endothelium Basement membrane Capillary Tunica Media None Capillary Tunica Externa
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Figure 21.1Comparative structure of blood vessels
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Three Types of Capillaries
Continuous Leaky Muscle, CT, lungs, CNS, Skin Fig 21.4
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Three Types of Capillaries
2. Fenestrated Leakier Kidneys, S.I, brain, eye, endocrine glands Fig 21.4
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Three Types of Capillaries
3. Sinusoids Leakiest Liver, red bone marrow, spleen Fig 21.4
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1-2 layers of smooth muscle
Venules (muscular) Microscopic Pass blood to veins Venule Tunica Interna Endothelium Basement membrane Venule Tunica Media 1-2 layers of smooth muscle Venule Tunica Externa Sparse
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Venules No more gas exchange Act as blood reservoirs
Helps regulate blood volume
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Postcapillary Venules
Tunica Interna Endothelium Basement membrane Tunica Media None Tunica Externa Sparse Microscopic
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Postcapillary Venules
Pass blood into muscular venules Permit exchange of nutrients and wastes between blood and interstitial fluid Very porous - Permit white blood cell immigration
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Veins Venous Tunica Interna Venous Tunica Media Venous Tunica Externa
Endothelium Valves Large lumen Basement membrane No internal elastic lamina Venous Tunica Media Much thinner than arteries No external elastic lamina Venous Tunica Externa Thickest layer
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Veins Range from 0.5mm-30mm Return blood to heart
Little compliance and vascular tone Valves Regulate blood flow Vascular (venous) sinuses Varicose veins
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Blood Vessel Topics 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
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Blood Distribution Because systemic veins and venules contain more than half the total blood volume, they are called blood reservoirs.
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Figure 21.6 Blood distribution in the cardiovascular system
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