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Blood Vessels

Blood Vessels. Blood Vessels. Arteries, Veins and Capillaries. Arteries. Carry blood away from the heart Distribute nutrients Under high pressure Structure Tunica Intima : inner layer Tunica Media : thick layer of smooth muscle for blood pressure regulation

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Blood Vessels

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  1. Blood Vessels

  2. Blood Vessels Arteries, Veins and Capillaries

  3. Arteries • Carry blood away from the heart • Distribute nutrients • Under high pressure • Structure • Tunica Intima: inner layer • Tunica Media: thick layer of smooth muscle for blood pressure regulation • Tunica Externa: thin outer layer of elastic tissue

  4. Veins • Carry blood towards the heart • Low pressure Levels • Structure • Tunica Intima: inner layer with valves to prevent back flow • Tunica Media: thin layer of smooth muscle • Tunica Externa: heavy layer in many veins

  5. Blood Vessels Arteries and Veins

  6. The Anatomy of a Blood Vessel Three Distinct Layers 1. Tunica interna (Aka, tunica intima) – the innermost layer • Provides a friction-free surface for blood flow 2. Tunica media – the middle layer • Contains concentric layers of smooth muscle cells • Layer responsible for vasoconstriction and vasodilation • This affects blood pressure and blood flow 3. Tunica externa (Aka, tunica adventitia) – the outermost layer • Composed mainly of collagen fibers interspersed with elastin fibers • Protects and reinforces the vessel

  7. Arteries – carry blood AWAY from the heart Types of Arteries: • Elastic (conducting) arteries • Arteries near the heart; largest in diameter • Contain more elastic fibers than any other vessel type, esp. in the tunica media • Enables the arteries to withstand and smooth out large pressure fluctuations • Expand and recoil to accommodate changes in blood volume – continuous flow of blood • Muscular (distributing) arteries • Deliver blood to specific body organs • Have the thickest tunica media of all vessels – more smooth muscle, less elastic fibers • Ex. Include: the external carotid arteries of the neck, brachial arteries of the arms, and femoral arteries of the thighs • Arterioles • The smallest of the arteries • Blood flow into the capillary beds is determined by arteriole diameter

  8. Capillaries • the site of chemical and gas exchange in the body’s tissues • thin walls make exchange easier Types of Capillaries: • Continuous capillaries – most common • Abundant in skin and muscles • Fenestrated capillaries • extremely permeable • ex. The kidneys, endocrine organs, and small intestines • Sinusoidal capillaries • allows for the passage of large molecules

  9. Veins – carry blood TO the heart Types of Veins: • Venules – formed when capillaries unite • Medium-sized veins • Large veins • Contain venous valves to prevent backflow

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