1. Cardiovascular system: Blood vessels, blood flow, blood pressure

2. Outline 1- Physical laws governing blood flow and blood pressure
2- Overview of vasculature
3- Arteries
4. Capillaries and venules
5. Veins
6. Lymphatic circulation
7. Mean arterial pressure and its regulation
8. Other cardiovascular regulatory processes

3. Outline 1- Physical laws governing blood flow and blood pressure
2- Overview of vasculature
3- Arteries
4. Capillaries and venules
5. Veins
6. Lymphatic circulation
7. Mean arterial pressure and its regulation
8. Other cardiovascular regulatory processes

4. Physical laws governing blood flow and blood pressure
Flow of blood through out body = pressure gradient within vessels X resistance to flow
- Pressure gradient: aortic pressure – central venous pressure
Resistance:
-- vessel radius
-- vessel length
-- blood viscosity

5. Factors promoting total peripheral resistance (TPR)
-- combined resistance of all vessels
-- vasodilation  resistance decreases
-- vasoconstriction  resistance increases

6. Outline 1- Physical laws governing blood flow and blood pressure
2- Overview of vasculature
3- Arteries
4. Capillaries and venules
5. Veins
6. Lymphatic circulation
7. Mean arterial pressure and its regulation
8. Other cardiovascular regulatory processes

7. Vasculature

8. Arteries and blood pressure
Pressure reservoir
Arterial walls are able to expand and recoil because of the pressure of elastic fibers in the arterial wall
Systolic pressure: maximum pressure occurring during systole
Diastolic pressure: pressure during diastole

9. Arterial blood pressure
Figure 14.8

10. Blood pressure values: what do they mean?
Pulse pressure:
PP = SP-DP
Mean arterial blood pressure = MABP
MABP = SBP + (2XDBP) 3
CO = MABP = SV x HR
TPR

11. Blood flow within each organ changes with body activities
Reminder: The ANS controls blood flow to the various organs
Figure 14.15

12. Outline 1- Physical laws governing blood flow and blood pressure
2- Overview of vasculature
3- Arteries
4. Capillaries and venules
5. Veins
6. Lymphatic circulation
7. Mean arterial pressure and its regulation
8. Other cardiovascular regulatory processes

13. Capillaries
Allow exchange of gases, nutrients and wastes between blood and tissues
Overall large surface area and low blood flow
Two main types:
- continuous capillaries: narrow space between cells  permeable to small or lipid soluble molecules
- fenestrated capillaries: large pores between cells large molecules can pass

14. Local control of blood flow in capillaries
Presence of precapillary sphincters on the arteriole and beginning of capillaries
Metarteriole: no sphincter  continuous blood flow  controls the amount of blood going to neighboring vessels

15. Movement of materials across capillary walls
Small molecules and lipid soluble molecules move by diffusion through the cell membrane
Larger molecules, charged molecules must pass through membrane channels, exocytosis or in between 2 cells
Water movement is controlled by the capillary hydrostatic and osmotic pressures

16. Forces controlling water movement
Arterial side of the capillary:
High capillary hydrostatic pressure (BHP), lower capillary osmotic pressure (BOP, due to proteins and other molecules in the blood)  Net filtration pressure pushes fluid from the blood toward the tissue (but the proteins remain in the capillary
Venous side of the capillary:
- Lower hydrostatic pressure (due to resistance) and higher capillary osmotic pressure  Net filtration pressure moves fluid back toward the capillary
Interstitial fluid hydrostatic (IFHP) and osmotic pressures (IFOP) remain overall identical

17. Fluid movement in the capillary
Arteriole side: fluid moves toward the tissues
Venous side: fluid reenters the capillary
Overall: for every 1 liter of fluid entering the tissues, only 0.85 l reenter the capillary
The remaining 0.15 l is reabsorbed as lymph by lymphatic capillaries and eventually returned back to blood circulation
When this system fails: Edema

18. Causes of edema
Increased interstitial hydrostatic pressure (lymphatic capillary blockage)
- breast cancer surgery, elephantiasis
Leaking capillary wall
- histamine release during allergic reaction
Increased hydrostatic blood pressure
- heart failure (left or right),
- excess fluid in the blood
Decreased blood osmotic pressure
Liver, kidney diseases, malnutrition (kwashiorkor), burn injuries

19. Outline 1- Physical laws governing blood flow and blood pressure
2- Overview of vasculature
3- Arteries
4. Capillaries and venules
5. Veins
6. Lymphatic circulation
7. Mean arterial pressure and its regulation
8. Other cardiovascular regulatory processes

20. Veins Veins are blood volume reservoir
Due to thinness of vessel wall  less resistance to stretch = more compliance

21. Factors influencing venous return
1- Skeletal muscle pump and valves 
2- Respiratory pump
3- Blood volume
4- Venomotor tone

22. Outline 1- Physical laws governing blood flow and blood pressure
2- Overview of vasculature
3- Arteries
4. Capillaries and venules
5. Veins
6. Lymphatic circulation
7. Mean arterial pressure and its regulation
8. Other cardiovascular regulatory processes

23. Lymphatic circulation
Driven by factors similar to venous circulation:
- muscle activity
- valves
- respiration
Lymph = plasma-proteins
Lymphatic circulation collects fluid not reabsorbed by the capillaries
Lymph is filtered in nodes before return to blood circulation

24. Outline 1- Physical laws governing blood flow and blood pressure
2- Overview of vasculature
3- Arteries
4. Capillaries and venules
5. Veins
6. Lymphatic circulation
7. Mean arterial pressure and its regulation
8. Other cardiovascular regulatory processes

25. Mean arterial pressure and its regulation
Regulation of blood flow in arteries
- Intrinsic control
- Extrinsic control
-- Neural control
-- Hormonal control
* Control of blood vessel radius
* Control of blood volume

26. Mean arterial pressure and its regulation
Regulation of blood flow in arteries
- Intrinsic control
- Extrinsic control
-- Neural control
-- Hormonal control
* Control of blood vessel radius
* Control of blood volume

27. Regulation of blood flow in arteries
It is important to adjust blood flow to organ needs  Flow of blood to particular organ can be regulated by varying resistance to flow (or blood vessel diameter)
Vasoconstriction of blood vessel smooth muscle is controlled both by the ANS and at the local level.
Four factors control arterial flow at the organ level:
- change in metabolic activity
- changes in blood flow
- stretch of arterial smooth muscle
- local chemical messengers

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

29. Mean arterial pressure and its regulation
Regulation of blood flow in arteries
- Intrinsic control
- Extrinsic control
-- Neural control
-- Hormonal control
* Control of blood vessel radius
* Control of blood volume

30. Extrinsic control of blood pressure
Two ways to control BP:
Neural control
Hormonal control
** Use negative feedback

31. Control of blood pressure
Importance: Blood pressure is a key factor for providing blood (thus oxygen and energy) to organs. SBP must be a minimum of 70 to sustain kidney filtration and adequate blood flow to the brain
CO= HR X SV = MABP/TPR 
MABP= HRxSVxTPR  heart rate, stroke volume
and peripheral resistance affect MABP
Main factors controlling BP: - Blood volume
- Blood vessel radius

32. Neural control of BP - 1
Baroreceptors: carotid and aortic sinuses sense the blood pressure in the aortic arch and internal carotid  send signal to the vasomotor center in the medulla oblongata
Other information are sent from the hypothalamus, cortex 

33. Neural control of BP - 2
The vasomotor center integrates all these information
The vasomotor sends decision to the ANS center:
Both parasympathetic and sympathetic innervate the S/A node  can accelerate or slow down the heart rate
The sympathetic NS innervates the myocardium and the smooth muscle of the arteries and veins  promotes vasoconstriction

34. Hormonal control of BP Control of blood vessel radius - Epinephrine
- Angiotensin II
- Vasopressin (?)
Control of blood volume
- Anti-diuretic hormone (vasopressin)
- Aldosterone
Control of heart rate and stroke volume
Hormones can control blood vessel radius and blood volume, stroke volume and heart rate
On a normal basis, blood vessel radius and blood volume are the main factors
If there is a critical loss of pressure, then the effects on HR and SV will be noticeable (due to epinephrine kicking in)

35. Control of blood vessel radius
Epinephrine: secreted by the adrenal medulla and ANS reflex  increase HR, stroke volume and promotes vasoconstriction of most blood vessel smooth muscles.
Angiotensin II  promotes vasoconstriction
Angiotensin II secretion:
Decreased flow of filtrate in kidney tubule is sensed by the Juxtaglomerular apparatus (a small organ located in the tubule)  secretion of renin
Renin activates angiotensinogen, a protein synthesized by the liver and circulating in the blood  angiotensin I
Angiotensin I is activated by a lung enzyme, Angiotensin-Activating Enzyme (ACE),  angiotensin II
Angiotensin II is a powerful vasoconstricted of blood vessel smooth muscles

36. Control of blood volume
Anti-diuretic hormone = ADH
Secreted by the posterior pituitary in response to ↑blood osmolarity (often due to dehydration)
Promote water reabsorption by the kidney tubules  H2O moves back into the blood  less urine formed

37. Control of blood volume
Aldosterone:
Secretion by the adrenal cortex triggered by angiotensin II
Promotes sodium reabsorption by the kidney tubules (Na+ moves back into the blood)
H2O follows by osmosis
Whereas ADH promotes H2O reabsorption only (in response to dehydration), aldosterone promotes reabsorption of both H2O and salt (in response to ↓ BP)

38. Clinical application: Shock
Stage I: Body reacts to maintain BP  ↑HR, vasoconstriction.. BP remains within normal range
Stage II: Body reacts to maintain BP  ↑HR, vasoconstriction.. BP drops below adequate range (SBP 70). Can be reversed by medical treatment
Stage III: Body is fighting to maintain adequate BP without success  HR is very high  not enough O2 for cardiac, brain cells to survive  damages. Cannot be reversed by medical treatment
Stage I: reversible, compensated shock
Stage II: reversible, noncompensated shock
Stage III: irreversible shock
Death