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Blood Vessels & Circulation

Blood Vessels & Circulation. Three Types of Blood Vessels. 1. Arteries Take blood away from heart Usually oxgenated Branch repeatedly Arterioles 2. Capillaries One cell thick Billions present Large surface area for nutrient exchange. Three Types of Blood Vessels. 3. Veins

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Blood Vessels & Circulation

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  1. Blood Vessels & Circulation

  2. Three Types of Blood Vessels 1. Arteries • Take blood away from heart • Usually oxgenated • Branch repeatedly • Arterioles 2. Capillaries • One cell thick • Billions present • Large surface area for nutrient exchange

  3. Three Types of Blood Vessels 3. Veins • Take blood to heart • Usually deoxygenated • Converge • Venules

  4. Tunics – Layers of Blood Vessels • Tunica intima • Endothelium • Lines vessels • Tunica media • Smooth muscle/elastic tissue • Changes vessel diameter • Vasodilation • Vasoconstriction • Tunica externa • Connective tissue covering

  5. What structural differences do you see?

  6. Structural Differences - Arteries • Very thick tunica media (Why?)

  7. Structural Differences - Veins • Thinner walls, larger lumens • Valves (Why?) • Three factors aiding in venous return • Valves • Respiratory pump • Skeletal muscles

  8. Structural Differences - Capillaries • Tunica intima only, one cell thick (Why?) • Capillary beds • True capillaries • Vascular shunts • Microcirculation

  9. Capillary Exchange • Substances move to and from body cells according to their concentration gradients • Before entering a cell, a substance must diffuse through the interstitial fluid

  10. Homeostatic Imbalances • Varicose Veins

  11. Homeostatic Imbalances • Atherosclerosis & arteriosclerosis

  12. Hydrostatic & Osmotic Pressure • Hydrostatic Pressure –governs the arterial end of the capillary bed; forces fluid out • Osmotic Pressure – governs the venous end of the capillary bed; draws fluid back in

  13. Vital Signs • Respiratory Rate • Body Temperature • Blood Pressure • Pulse– pressure wave of blood; measure at Pressure Points

  14. Blood Pressure

  15. Measuring Blood Pressure • Two measurements using a sphygmomanometer: • Systolic– Pressure at peak of ventricular contraction • Diastolic – Pressure when ventricles relax

  16. Blood Pressure Gradient • Highest in aorta • Lowest in vena cava

  17. Measuring Blood Pressure • Sounds of Korotkoff • Systolic pressure – 1st tapping sound when blood squirts through constricted artery • Diastolic pressure – sounds disappear, blood flows freely • Ex. A normal reading of 120/75 mmHg • 120 systolic pressure/75 diastolic pressure

  18. Blood Pressure (BP) BP = CO x PR where • CO = cardiac output = heart rate x stroke volume • PR = peripheral resistance • The amount of friction encountered by the blood as it flows through the blood vessel

  19. Factors Affecting Cardiac Output

  20. Factors Affecting Peripheral Resistance • Viscosity – fairly constant in a healthy person What could cause an increased viscosity?

  21. Factors Affecting Peripheral Resistance • Neural factors • Vasoconstriction • Vasodilation

  22. Factors Affecting Peripheral Resistance • Renal factors • The kidney retains or releases water in urine to regulate BP levels • If BP is low, kidneys release renin, which is converted to angiotensin, a vasoconstrictor. It also causes aldosterone release, retaining salt and increasing water levels.

  23. Factors Affecting Peripheral Resistance • Chemicals • Nicotine - BP by vasoconstriction… and then you DIE! • Alcohol – BP by vasodilation • Epinephrine – HR and BP

  24. Factors Affecting Peripheral Resistance • Diet and Exercise • High salt, saturated fats, cholesterol = BP • Each extra pound of fat, requires miles of additional blood vessels = BP

  25. Homeostatic Imbalance • Hypertension – sustained high blood pressure (140/90 or greater)

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