Blood Vessels & Circulation

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

5. 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

6. What structural differences do you see?

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

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

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

10. 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

11. Homeostatic Imbalances • Varicose Veins

12. Homeostatic Imbalances • Atherosclerosis & arteriosclerosis

13. 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

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

15. Blood Pressure

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

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

18. 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

19. 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

20. Factors Affecting Cardiac Output

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

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

23. 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.

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

25. 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

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