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Fig. 9-3, p.361

Plasma = 55% of whole blood. Platelets. “Buffy coat” <1%. White blood cells. Packed cell volume, or hematocrit. Red blood cells = 45% of whole blood. Fig. 9-3, p.361. Platelet. Adenosine. diphosphate. (ADP). Exposed collagen. Aggregating. Prostacyclin. Prostacyclin.

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Fig. 9-3, p.361

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  1. Plasma = 55% of whole blood Platelets “Buffy coat” <1% White blood cells Packed cell volume, or hematocrit Red blood cells = 45% of whole blood Fig. 9-3, p.361

  2. Platelet Adenosine diphosphate (ADP) Exposed collagen Aggregating Prostacyclin Prostacyclin Normal endothelium Normal endothelium Collagen at site of platelet plug and nitric acid and nitric acid vessel injury Vessel Inhibits platelet Vessel wall aggregation lumen Fig. 9-9, p.368

  3. Fig. 9-11, p.369

  4. Goals • To describe the general structure of blood vessel walls. • To compare and contrast the types of blood vessels. • To relate the blood pressure in the various parts of the vascular system to differences in blood vessel structure.

  5. Peripheral Circulation • Arteries • Arterioles • Capillaries • Veins • Role is to direct the flow of blood from the heart to the capillaries, and back to the heart.

  6. Arteries • Elastic arteries: • Walls of smooth muscle and elastin. • Expand when the pressure of the blood rises. • Acts as recoil system when ventricles relax. • Muscular arteries: • Are less elastic and have a thicker layer of smooth muscle. • Arterioles: • -Contain highest % smooth muscle. • -Greatest pressure drop. • -Greatest resistance to flow.

  7. Capillaries • Capillaries consist of only a thin tunica intima or endothelium. • Most capillaries are arranged in capillary beds. • Thinness allows exchange of materials between blood and tissues.

  8. Capillaries • Smallest blood vessels. • 1 endothelial cell thick. • Provide direct access to cells. • Permits exchange of nutrients and wastes.

  9. The velocity of flow at any point in the circulation is not related to the proximity of the heart, but to the total cross-sectional area of that part of the circulation.

  10. Venules

  11. Veins • Venules: • Formed when capillaries unite. • Very porous. • Veins: • Little smooth muscle or elastin. • Capacitance vessels (blood reservoirs). • Contain 1-way valves ensure blood flow to the heart.

  12. Summary 1. Of the three types of vessels, arteries have the thickest tunica media (allowing stretch/recoil and vasoconstriction), veins have relatively thick tunica adventitia, and capillaries are the thinnest (allowing exchange of materials.) 2. Blood pressure varies in different parts of the vascular system. At least part of this variation reflects vessel structure. Structural adaptations of veins assist in returning blood to the heart.

  13. Sources of Peripheral Resistance • Three main sources of peripheral resistance: 1. blood vessel diameter 2. blood viscosity 3. total vessel length

  14. Total Blood Vessel Length Affects Peripheral Resistance • Increased fatty tissue requires more blood vessels to service it and adds to the total vessel length in the body. • The longer the total vessel length, the greater the resistance encountered, and the greater the blood pressure.

  15. Blood Pressure Regulation • short-term mechanisms, which regulate blood vessel diameter, heart rate and contractility • long-term mechanisms, which regulate blood volume

  16. Long-Term Regulation of Low Blood Pressure • Long-term regulation of blood pressure is primarily accomplished by altering blood volume. • The loss of blood through hemorrhage, accident, or donating a pint of blood will lower blood pressure and trigger processes to restore blood volume and therefore blood pressure back to normal. • Long-term regulatory processes promote the conservation of body fluids via renal mechanisms and stimulate intake of water to normalize blood volume and blood pressures.

  17. Kidney Juxtaglomerular Cells • Juxtaglomerular cells in the kidney monitor alterations in the blood pressure. If blood pressure falls too low, these specialized cells release the enzyme renin into the bloodstream.

  18. Step 1: Renin-Angiotensin Mechanism: angiotensinogen renin angiotensin I As renin travels through the bloodstream, it binds to an inactive plasma protein, angiotensinogen, activating it into angiotensin I.

  19. Step 2: Conversion of Angiotensin I Converting Angiotensin I to Angiotensin II: As angiotensin I passes through the lung capillaries, an enzyme in the lungs converts angiotensin I to angiotensin II. angiotensin I angiotensin II enzyme

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