1. The Cardiovascular System: Blood Vessels and Circulation

2. Blood Vessels Arteries- from heart
Elastic => large
Muscular => distribution to organs
Arterioles => distribution to capillaries- mostly muscle
Capillaries- thin walled for diffusion
Veins- to heart
Venules => from capillaries
Veins from tissue to vena cavae to heart
Blood Vessels

3. Figure 16.1ab

4. Figure 16.1c

5. Blood Vessel Structure
Three layers
Tunica Intima (Interna)- Innermost, endothelial layer
Tunica Media- Middle, muscular layer
Tunica Externa- Outermost layer
Blood Vessel Structure

6. Blood Vessel Structure
Differences
Arteries-> thicker tunica media
Elastic tissue and/or muscle
As they get smaller-> more muscle
Arterioles-> very muscular- control
Veins- bigger lumen and thinner walls
Veins-> valves to prevent backflow
Venules very thin, no valves
Blood Vessel Structure

7. Vessel Functions Differences
Muscular arteries & arterioles regulate flow
Sympathetic activity to smooth muscle vasoconstriction (narrowing)
Decreased sympathetic activity or NO causes relaxation or vasodilation
Arterioles adjust flow into capillaries
Systemic veins & venules serve as blood reservoirs (~64% total blood volume)
Vessel Functions

8. Capillary Details Capillaries only have endothelium
Very thin cells & cell nuclei protrude into lumen- easy diffusion
Connected from arterioles to venules in networks
Sometimes direct route from arteriole to venule
Filling controlled by small arterioles & precapillary sphincters
Capillary Details

9. Figure 16.2a

10. Figure 16.2b

11. Capillary Exchange Slow flow through capillaries Blood pressure 
Allows time for exchange through wall
Blood pressure 
filtration of fluid out of capillary
Mostly in first ½ of vessel length
Osmosis (protein concentration)
Reabsorption of fluid from outside to inside
Mostly in last ½ of vessel length
Balance determines fluid in circulation
Excess fluid returned via lymphatic system
Local signals can adjust capillary flow
Capillary Exchange

12. Figure 16.3

13. Venous Return Blood enters veins at very low pressure.
Needs more pumping to get back to heart
= action of heart; muscle pumps; respiratory pump
Some pressure from heart action
Not enough to overcome gravity
Venous Return

14. Muscle & Respiratory Pumps
Contracting skeletal muscles squeeze veins emptying them
Venous valves flow is toward heart
Respiratory pump has similar action
Inhalation decreased thoracic pressure & increased abdominal pressure
Blood flows toward heart
Exhalation allows refilling of abdominal veins
Muscle & Respiratory Pumps

15. Figure 16.4

16. From high pressure area to lower pressure area, i. e
From high pressure area to lower pressure area, i.e. down pressure gradient
Greater gradient greater flow
Ventricular contraction blood pressure (BP)
Highest in aorta and declines as flows through vessels
mmHg in aorta ~16 mmHg at venules 0 at R. Atrium
Resistance= opposition to flow
Blood Flow

17. Resistance Depends on: Vessel lumen diameter
Smaller lumen  greater resistance
Blood viscosity (thickness)
Higher viscosity greater resistance
Viscosity of blood depends on Hct
Total vessel length
Longer the length of flow the more friction with wall
Total body resistance increases with growth and addition of tissue
Resistance

18. Figure 16.5

19. Regulation of Blood Pressure & Flow
Fast responses: e.g. standing up
Slower responses: e.g. blood volume
Distribution: e.g. to working muscles
Balance of CO (cardiac output) with flow to body
Interacts with many other control systems
Cardiovascular (CV) Center major regulator
Regulation of Blood Pressure & Flow

20. Inputs Higher centers: Sensory receptor input: Cerebral cortex,
Limbic system
Hypothalamus
Flow adjusted for body temperature
Sensory receptor input:
Proprioceptors
Baroreceptors
Chemoreceptors
Inputs

21. Inputs Proprioceptors: Baroreceptors: in aorta & carotid
Start HR change as activity starts
Baroreceptors: in aorta & carotid
pressure   parasympathetic &
 sympathetic stimulation  CO
Chemoreceptors: in aorta & carotid
Low O2, high H+, CO2  vasoconstriction  BP
Inputs

22. Figure 16.6

23. Output ANS to heart  Sympathetic  HR &  force of contraction
 Parasympathetic  HR
Vasomotor
To arterioles  vasomotor tone (vasoconstriction)
To veins move blood to heart  BP
Output

24. Hormone regulation Renin-Angiotensin system
Angiotensin II  vasoconstriction+ thirst
 aldosterone   Na+ & water loss in urine on
Epinephrine & Norepinephrine  CO
ADH = Vasopressin
constriction   BP
Thirst & water retention in kidney BP
ANP- from cells in atria
Vasodilation & loss of salt & water in urine BP
Hormone regulation

25. Figure 16.7

26. Checking Circulation- Pulse
Pulse in arteries = HR (Heart Rate)
Use radial artery at wrist
carotid artery- neck
brachial artery- arm
Tachycardia = rapid rest rate (>100 bpm)
Bradycardia= slow rest rate (<50 bpm)
Checking Circulation- Pulse

27. Blood Pressure Arterial Blood Pressure Systolic pressure
Peak arterial pressure during ventricular systole
Diastolic pressure
Minimum arterial pressure during diastole
Blood Pressure

28. Blood Pressure Use sphygmomanometer Raise pressure above systolic-
Usually on brachial artery
Raise pressure above systolic-
stop flow
Lower pressure in cuff until flow just starts
first sound  Systolic Pressure
Lower until sound suddenly gets faint
Diastolic pressure
Blood Pressure

29. Blood Pressure Normal = 120/80 Hypertension Hypotension
Abnormally high blood pressure
Greater than 140/90
Hypotension
Abnormally low blood pressure
Less than 90/60
Blood Pressure

30. Aging Stiffening of aortae Loss of cardiac muscle strength
Reduced CO & increased systolic pressure
Coronary artery disease
Congestive heart failure
Atherosclerosis
Aging

31. Anatomy of Blood Vessels

32. Blood flow through Vessels
From Heart Arteries Arterioles Capillaries Venules Veins To Heart
Blood flow through Vessels

33. Figure 16.1ab

34. Figure 16.1c

35. Blood Vessel Structure
Three layers
Tunica Intima (Interna)- Innermost, endothelial layer
Tunica Media- Middle, muscular layer
Tunica Externa- Outermost layer
Blood Vessel Structure

36. Blood Vessel Structure
Differences
Arteries-> thicker tunica media
Veins- bigger lumen and thinner walls, valves to prevent backflow
Capillaries only have endothelium
Blood Vessel Structure

37. Circulatory Routes Two parts: Systemic & Pulmonary
Systemic circulation- throughout body
Oxygenated blood deoxygenated as it goes
All systemic arteries branch from aorta
All systemic veins empty into Superior Vena Cava, Inferior Vena Cava or the Coronary Sinus
Carry deoxygenated blood to heart
Circulatory Routes

38. Pulmonary Circulation
From right ventricle pulmonary trunk
R. & L. pulmonary arteries
Carry deoxygenated blood
 R. & L. lungs
Gas exchange occurs
 2 R. & 2 L. pulmonary veins
Carry oxygenated blood
 L. atrium
Pulmonary Circulation

40. Pulmonary circuit (veins) Systemic circuit (arteries)
Brain
Upper limbs
Pulmonary circuit (veins)
Lungs LA
Systemic circuit (arteries)
Left ventricle
Kidneys
Spleen
Digestive organs
Liver
Gonads
Lower limbs 40

41. Pulmonary circuit (arteries) Systemic circuit (veins)
Brain
Upper limbs
Pulmonary circuit (arteries)
Lungs RA
Right ventricle
Systemic circuit (veins)
Kidneys
Digestive organs
Liver
Gonads
Lower limbs 41