Blood Vessels

1. Blood Vessels Chapter 19 – Day 1

2. Blood Vessel Structure Fig. 19.1

3. Blood Vessels - Intro • Blood vessels are essentially a “pipeline” to: • Carry blood TO parts of the body = arteries • Carry blood BACK FROM parts of the body = veins • Subdivisions • Pulmonary blood vessels: blood to the lungs and back • Systemic blood vessels: blood to and from the rest of the body

4. Blood Vessels - Intro • Veins = mostly deoxygenated – except pulmonary vein & umbilical vein • Arteries = mostly oxygenated – except pulmonary artery & umbilical artery • Capillaries = interconnecting vessels • Enable gas exchange, etc. • Blood vessel structure and comparison activity in lab

5. Blood Vessel Structure Fig. 19.1

6. Arteries vs. Veins - Similarities 3 Layers • Tunica Externa • Connective Tissue • Tunica Media • Smooth muscle cells • Elastic fibers (arteries) • Collagen fibers • Tunica Interna • Elastic layer • Endothelial cells & connective tissue with elastic fibers (arteries)

7. Arteries vs. Veins • Arteries are thick walled • Larger arteries have more elastic fibers • Tunica media – thicker, concentric & longitudinal • Tunica interna – internal elastic membrane • ARTERIES • Elasticity • Ability to stretch when full = high pressure • Return to their original state when relaxed • Contractability • More smooth muscle (than veins) • Vasodilation, Vasoconstriction • Both veins & large arteries need O2 – supplied by vaso vasorum

8. Arteries vs. Veins • Hierarchy of organization • (learn examples from text) • Largest vessels coming out of heart or to heart • These carry the most volume • If arteries – they have the highest pressure • Diagram on board and Fig. 19.2 • Be able to work though these – know order and characteristics

9. Blood Vessel Hierarchy Fig. 19.2

10. Capillaries Fig. 19.5

11. Arteries vs. Veins • Different jobs and different driving forces • Arteries • Force of contraction pushes blood forward • Blood pressure = driving force • Moves downhill to lower extremities - gravity • Veins • Lower extremities to heart = against gravity • Low pressure • Relies on other driving forces

12. Veins • Two features help to push blood forward: • Valves – keep blood from flowing backward (flow is possible in 1 direction only) • Skeletal muscle contraction • Helps to push blood forward • Breathing action • Pressure in chest helps venous flow • All contribute to venous return Fig. 19.6

13. Blood vessel function • Ultimately blood delivers O2 & nutrients to tissues as well as removing wastes • How does this happen? • Any organ: • Blood vessels (in & out): arteries – smallest branch = capillary • The organ is infused with capillaries • Nutrient exchange occurs at this level • In the capillaries – only the endothelial layer is present • Substances in the capillaries move to the Interstitial Fluid → then into cells

14. O2, Nutrient, and Waste Exchange • Waste products are released into the interstitial fluid • Waste products are then taken up by fenestrated capillaries because they are typically large molecules (recall differences between fenestrated & continuous capillaries) Fig. 19.4

15. O2, Nutrient, and Waste Exchange • Exchange between blood and interstitial fluid • Simple (& Facilitated) Diffusion: • In response to a concentration gradient • Filtration • Force pushes out substances – based on pressure • Osmosis • Reabsorption of water

16. Diffusion • Ions and small organic molecules (glucose, amino acids, urea – move through pores in fenestrated capillaries or move via diffusion between endothelial cells of adjacent capillaries • Ions (Na+, K, etc.) diffuse across endothelial cells by passing through channels in cell membranes • Large water-soluble compounds can only work enter or leave blood stream via fenestrated capillaries • Lipids (FAs, steroids) and lipid-soluble compounds (esp. CO2, O2) cross capillary walls by diffusion through endothelial cell membranes • Plasma proteins can only diffuse through in sinusoids (such as those in the liver)

17. Filtration • Driving force = PRESSURE in capillary = Capillary Hydrostatic Pressure (CHP) • Water is forced across a capillary wall and small solutes travel with the water • Through endothelial cells or pores of fenestrated capillaries Fig. 19.11

18. Reabsorption • Occurs as a result of osmosis • Diffusion of water across selectively permeable membrane • Remember, water molecules move toward soln with higher solute concentration • Process by which dissolved solutes is moved • Osmotic pressure = amount of pressure that must be applied to prevent osmotic movement across a membrane (Blood Osmotic Pressure = BOP; IOP=?) • BCOP = blood colloid osmotic pressure = osmotic pressure of blood (also BOP) • Remember…hydrostatic pressure forces water OUT of solution, whereas osmotic pressure draws water INTO a solution (BHP vs. IOP; BOP vs. IFHP)

19. Pressures have to be balanced so that fluid in and out can be coordinated – refer to handout (review!!) Fig. 19.11

20. Filtration & Reabsorption • If BHP > BOP in the blood vessel, fluid is pushed out • If BHP < BOP fluid enters in • IFHP & IOP – low & stable because there are fewer proteins in interstitial fluid • Net Filtration Pressure is the difference between the net hydrostatic pressure and the net osmotic pressure: • Net filtration = net hydrostatic – net colloid pressure pressure osmotic pressure • If positive fluid moves OUT of capillary • If negative fluid moves INTO capillary

21. Equilibrium • Analogy to filtration experiment • Charcoal = cells & proteins • CuSO4 = nutrients & O2 • Cells & Proteins remain in blood vessel • H2O, hormones, other chemicals, nutrients, O2, glucose, ions = pushed out • Equilibrium between arterial & venus ends maintains proper pressure differences (Starling’s Law of Capillaries) • Excess fluid expelled into tissues causes an increase in interstitial fluid – if in excess, causes EDEMA • Excess fluid buildup, swollen ankles, etc Read in book and follow handout

22. Equilibrium • Equilibrium between arterial & venus ends maintains proper pressure differences • Excess fluid expelled into tissues causes an increase in interstitial fluid – if in excess, causes EDEMA • Excess fluid buildup, swollen ankles, etc Read in book and follow handout • Different demands for gas and nutrient exchange • For proper delivery – the cardiovascular system depends on: • Cardiac Output • Peripheral Resistance • Blood Pressure

23. St

24. Blood Pressure and Blood Vessels • Blood Pressure • Pressure within blood vessels • Influenced by cardiac output, but other factors are involved as well • Vasomotor tone • Muscle tone of smooth muscle • Resistance against blood • This is controlled by the medulla in the brain • VASOCONSTRICTION - ↑ sympathetic impulse • VASODILATION - ↓ sympathetic impulse • THESE CHANGES AFFECT BLOD PRESSURE

25. Blood Pressure and Blood Vessels • Blood Pressure • Vasomotor tone • Baroreceptors • Monitor the degree of stretch • Special receptor nerve cells in specific areas of the body • Baroreceptors adjust cardiac output & resistance • Chemoreceptors • Special nerve cells sensitive to chemical concentrations • These sense arterial levels of CO2, O2, H+ (pH), • Can adjust constriction based on the concentration of these chemicals

26. Blood Pressure and Blood Vessels • Blood Pressure • Cerebral Cortex • Stress, anger, depression • All of these emotions affect the sympathetic division of the nervous system • The cerebral cortex alters blood pressure/flow by altering levels of vasoconstriction/vasodilation • Local Changes • Sphincters near capillaries • Chemicals • Drugs • Alter vasodilation & constriction

27. Hypertension • Abnormally high BP levels (>150/90) • Approximately 25% of the population suffers from hypertension • Cause & Effects • uncertain • Heart works harder – O2 demand is high • Hypertension: accelerates artherosclerosis, increases clot formation, causes kidney damage • Treatment • To reduce heart workload • Diuretics - ↓ blood volume (increasing urine output) • Vasodilators – relax smooth muscle • β – blockers: affects sympathetic receptors (reduces cardiac output) • CA2+ blockers: reduce cardiac output

28. Other Vessel Disorders • Varicose veins • Hemorrhoids • Circulatory Shock • Hematogenic Shock • Cardiogenic Shock • Neurogenic Shock • Septic Shock

29. Equilibrium • Need constant control of these factors to maintain homeostasis = CARDIOVASCULAR REGULATION • Controlled by • Autoregulation Mechanisms • Local factors change pattern of blood flow w/in capillary beds • Response to chemical changes in interstitial fluids • Neural Mechanisms • Respond to changes in arterial pressure or blood gas levels @ a specific site stimulates cardiovascular centers of ANS • Endocrine Mechanisms • Releases hormones that enhance short-term adjustments and direct long-term changes in cardiovascular performance

30. Auto Regulation • Local changes • Sphincters near capillaries are adjusted • Depend on local VASODILATION & VASOCONSTRICTION chemicals (nitrous oxide) – know examples from text (p 547) • Vasodilator: factor(s) that promote the dilation of precapillary sphincters • Local vasodilators act at the tissue level & accelerate blood flow through the tissue of origin

31. Neural Mechanisms • Neural Mechanisms • Sympathetic division controls… • Smooth muscle tone (vasomotor tone) • Increased sympathetic impulses ( vasoconstriction) • Decreased sympathetic impulses ( vasodilation) • Receptors

32. Capillaries Fig. 19.5