1. Blood Flow and Blood Pressure

2. Cardiovascular System Functions
Heart, blood vessels, and blood work to transport
Oxygen and nutrients to cells
Wastes from cells to liver and kidneys
Hormones, immune cells, and clotting proteins to specific target cells
Maintain pressure in vessels so blood will flow to organs and tissues

3. heart  arteries  arterioles capillaries  venules  veins
Blood Vessels
heart  arteries  arterioles capillaries  venules  veins
Arteries—relatively large, main vessels that conduct blood away from the heart
Arterioles—small branching vessels in peripheral tissues that decrease in diameter (increase in resistance)
Capillaries—where diffusion takes place between blood and interstitial fluid (ECF; 3rd space)
Venules—collect blood from capillaries
Veins—return blood to heart

4. Blood Vessels Blood vessel walls have three layers:
Tunica intima, media, and externa

5. Capillary Fluid Exchange
Fluid circulates between capillary blood and interstitium to move nutrients into the interstitial fluid (ISF) for cell use and wastes out of the ISF for removal by blood
Fluid movement occurs via osmosis (not transport) through openings between adjacent endothelial cells
Fluid movement in to interstitium is driven by hydrostatic pressure
Fluid movement into blood is driven by osmotic pressure (oncotic pressure)

6. Capillary Filtration Filtration (movement of fluid in to interstitium)
Driven by hydrostatic pressure (pressure in the vessel/ MAP)
Water and small solutes forced through gaps between endothelial cells
Leaves larger solutes (glucose + albumins) in bloodstream

7. Capillary Hydrostatic Pressure

8. Capillary Reabsorption
Reabsorption (movement of fluid back into capillary)
Driven by blood colloid osmotic pressure
Slightly higher colloid osmotic pressure in blood (6-8%) vs. interstitium due to suspended blood proteins (albumin) that are too large to cross capillary walls

9. Fluid Movement

10. Capillary Exchange of Fluid
At arterial end of capillary
Fluid moves into interstitial fluid because hydrostatic pressure is higher than blood colloid osmotic pressure
At venous end of capillary
Fluid moves out of interstitial fluid because hydrostatic pressure is less than blood colloid osmotic pressure
capillary fluid movement animation

11. Fluid Recycling
Capillaries filter more out (24 L/day) than they reabsorb (20 L/day)
Excess fluid enters lymphatic vessels
Ensure constant plasma and interstitial fluid communication
Accelerate distribution of nutrients, hormones, and dissolved gases through tissues
Transport insoluble lipids and tissue proteins that cannot cross capillary walls
Flush bacterial toxins and chemicals to immune system tissues

12. Capillary Dynamics
When does CHP and how does that affect filtration and reabsorption?
When does BCOP and how does that affect filtration and reabsorption?

13. Capillary Dynamics
Dehydration—lose H2O/decrease in blood volume, so how does that affect CHP and BCOP?
Increases BCOP and decreases CHP
Accelerates reabsorption (why????)
Excess blood volume—how does that affect CHP and BCOP?
Increased CHP
Decreased BCOP
Accelerates filtration (why??) resulting in edema
Hemorrhaging
Reduces CHP and NFP and this leads to increased reabsorption of interstitial fluid (recall of fluids)

14. Capillary Dynamics Dehydration can be caused by:
Loose water to environment so blood volume decreases
Decrease in hydrostatic pressure
Increase in plasma protein concentration

15. Capillary Dynamics Edema can be caused by several factors:
Increase in capillary permeability-leaky capillaries via trauma, or histamine release due to inflammation or allergic reaction
Decrease in plasma protein concentration-burns, malnutrition or cirrhosis of the liver
Increase in hydrostatic pressure-cardiac/ renal failure, obstruction of blood flow, lymphatic obstruction (breast cancer surgery), or increase in blood volume

16. Blood Flow Rate
The cardiovascular system is regulated to ensure blood flow through capillaries in periphery
Why?
The heart must generate enough pressure to overcome vessel resistance to keep blood flowing
CO=SV X HR

17. Blood Flow Rate
Flow rate=volume of blood that flows through the systemic circuit per minute
Flow rate is dependent on pressure differences and resistance within the cardiovascular system
F= ∆ P/R
Flow rate is directly proportional to pressure difference
Flow rate is indirectly proportional resistance

18. Blood Flow Rate Flow rate= ∆ P/R
Capillaries regulate flow rate at the tissue level intrinsically
Cardiovascular control centers regulate flow rate on a large scale (via heart and blood vessels) extrinsically

19. Pressure Gradient (∆P)
Blood flows from high low pressure
The pressure gradient (∆P) = P at one end of a blood vessel - P at the other end of a blood vessel
The greater the difference is=the faster blood flows
How is our pressure gradient maintained?

20. Systemic Circuit Pressure Gradient

21. Systemic Circuit Pressure Gradient
∆ P= aortic pressure- vena cava pressure
∆ P= MAP- CVP
∆ P= MAP- 0
∆ P= MAP

22. Pressure Gradient Across Both Circuits

23. Pulmonary Pressure Gradient
Pulmonary pressure gradient = pressure in pulmonary arteries - pressure in pulmonary veins
Pulmonary arterial pressure = 15 mm Hg
Pulmonary venous pressure = 0 mm Hg
Pressure gradient (∆P) =15-0=15 mm Hg
Is this higher or lower than ∆P for systemic circuit?

24. Blood Flow, Pressure and Resistance
∆P systemic circuit > ∆P pulmonary circuit
However, flow through both circuits are equal
HOW???

25. Blood Flow, Pressure and Resistance
Resistance through pulmonary circuit < systemic circuit

26. Resistance Flow through network is dependent on resistance (TPR)
Poiseulle’s Law
R= 8Lη/ π r4
Resistance (R) is due to:
Length of vessel (L)
Viscosity of fluid = 
dependent on amount of RBC’s and plasma proteins
Internal radius of vessel (r4)
arterioles (and small arteries) can regulate their radii

27. Resistance
Which body position yields more resistance to blood flow laying down or standing and why?
How does your body deal with this?

28. Blood Flow Regulation
Figure 15-10

29. Resistance
Regulation of radius of arterioles (and small arteries) intrinsically or extrinsically
Vasodilation
Increase radius  decrease resistance increase flow
Vasoconstriction
Decrease radius  increase resistance decrease flow

30. Intrinsic Control of Arterioles
Changes in blood flow
- decreased blood flow  increased metabolic wastes  vasodilation increase blood flow
Stretch of arterial wall (myogenic response)
- Stretch of arterial wall due to increased pressure  reflex constriction
Change in metabolic activity
Usually linked to CO2 and O2 levels (↑ CO2  vasodilation ↑ blood flow)
Locally secreted chemicals can promote vasoconstriction or most commonly vasodilation
- inflammatory chemicals (histamine, nitric oxide)

31. Extrinsic Control of Arterioles
Baroreceptor Reflex

33. Factors That Influence MAP
Figure 15-10

34. Blood Pressure Regulation
Blood volume is regulated by kidneys via the Renin-Angiotensin-Aldosterone System and by heart via atria natriuretic peptides
Blood osmolarity is regulated by kidneys via antidiuretic hormone

35. Renin-Angiotensin-Aldosterone System
When you have low
blood volume
RAAS animation

36. Atrial Natriuretic Peptide
When you have high blood volume

37. Antidiuretic Hormone Blood osmolarity regulation
When you are dehydrated
you have high blood osmlarity

38. Regulation of Blood Pressure
Figure 21–13 Short-Term and Long-Term Cardiovascular Responses