1. Cardio #2

2. 15.4: Blood Vessels
The blood vessels are organs of the cardiovascular system
The blood vessels form a closed circuit to and from the heart
The blood vessels include:
Arteries - carry blood away from the ventricles of the heart
Arterioles - receive blood from the arteries and carry blood to the capillaries
Capillaries - sites of exchange of substances between the blood and the body cells
Venules - receive blood from the capillaries
Veins - carry blood toward the atria of the heart

3. (elastic and collagenous fibers)
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Artery
Vein
Lumen
Valve
Endothelium of
tunica interna
Connective tissue
(elastic and collagenous fibers)
Tunica media
Tunica externa
(a)
(b)
Endothelium
of tunica
interna
Lumen
Middle layer
(tunica
media)
Outer layer
(tunica
externa)
c: © The McGraw-Hill Companies, Inc./Al Telser, photographer
(c)

4. Arteries and Arterioles
Thick strong wall (three layers or tunics)
Endothelial lining
Middle layer of smooth muscle and elastic tissue
Outer layer of connective tissue
Carries blood under relatively high pressure
Arterioles:
Thinner wall than an artery (three layers or tunics)
Middle and outer layers are thinned
Some smooth muscle tissue
Small amount of connective tissue
Helps control blood flow into a capillary

5. Arteriole Smooth muscle cell Endothelium Precapillary sphincter
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Arteriole
Smooth
muscle cell
Endothelium
Precapillary
sphincter
Capillary 5

6. Capillaries Capillaries are the smallest diameter blood vessels
They connect the smallest arteriole and the smallest venule
They are extensions of the inner lining of arterioles
The walls are endothelium only
They are semi-permeable
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Metarteriole (forming arteriovenous
shunt)
Precapillary
sphincter
Arteriole
Capillaries
Venule
Artery
Vein
Blood flow
Blood flow

7. b,c, : © Don. W. Fawcett/Visuals Unlimited
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Tissue fluid
Nucleus of
endothelial
cell
Endothelial cell
Endothelial
cell cytoplasm
Lumen of
capillary
Slit
Cell junction
(b)
Tissue fluid
Capillary
(a)
(c)
b,c, : © Don. W. Fawcett/Visuals Unlimited

8. © Don. W. Fawcett/Visuals Unlimited
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Arteriole
Capillary
Venule
© Don. W. Fawcett/Visuals Unlimited

9. Net force at arteriolar end Net force at venular end
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Lymphatic
capillary
Tissue
cells
Outward force,
including
hydrostatic
pressure
16 mm Hg
Blood
flow
from
arteriole
Net outward
pressure
11 mm Hg
Net inward
pressure
8 mm Hg
Outward force,
including
hydrostatic
pressure
35 mm Hg
Blood
flow to
venule
Capillary
Inward force
of osmotic
pressure
24 mm Hg
Inward force of
osmotic pressure
24 mm Hg
Net force at arteriolar end
Net force at venular end
Outward force, including hydrostatic pressure = 35 mm Hg
Outward force, including hydrostatic pressure = 16 mm Hg
Inward force of osmotic pressure = 24 mm Hg
Inward force of osmotic pressure = 24 mm Hg
Net outward pressure = 11 mm Hg
Net inward pressure = 8 mm Hg

10. Venules and Veins Venule:
Microscopic vessels that continue from the capillaries and merge to form veins
Thinner walls than arterioles
Less smooth muscle and elastic tissue than arteriole
Veins:
Thinner walls than arteries (three layers or tunics)
Middle wall poorly developed
Many have flap-like valves
Carry blood under relatively low pressure
Function as blood reservoirs

11. Toward heart (a) (b) 100 90 80 70 60 Large veins Percent distribution
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
100 90 80 70 60
Large
veins
Percent distribution 50 40
Toward
heart 30
Small
veins
and
venules 20 10
Systemic
veins
60–70%
Lungs
10–12%
Heart
8–11%
Systemic
arteries
10–12%
Capillaries
4–5%
(a)
(b)

13. 15.5: Blood Pressure
Blood pressure is the force the blood exerts against the inner walls of the blood vessels

14. Arterial Blood Pressure
Rises when the ventricles contract
Falls when the ventricles relax
Systolic pressure is the maximum pressure during ventricular contraction
Diastolic pressure is the minimum pressure when the ventricles relax

15. Temporal a. Facial a. Carotid a. Brachial a. Radial a. Femoral a.
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Temporal a.
Facial a.
Carotid a.
Brachial a.
Radial a.
Femoral a.
Popliteal a.
Posterior tibial a.
Dorsalis pedis a.

16. Factors That Influence Arterial Blood Pressure
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Blood volume
increases
Heart rate
increases
Stroke volume
increases
Blood pressure increases
Blood viscosity
increases
Peripheral resistance
increases

17. Control of Blood Pressure
Blood pressure (BP) is determined by cardiac output (CO) and peripheral resistance (PR) according to this relationship: BP = CO x PR
Maintenance of blood pressure requires regulation of these two factors
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Increased blood pressure
Decreased heart rate
Decreased stroke volume
Decreased cardiac output
Decreased peripheral resistance
Blood pressure maintained
Increased cardiac output
Increased peripheral resistance
Increased heart rate
Increased stroke volume
Decreased blood pressure

18. Stimulation of baroreceptors in aortic arch and carotid sinuses
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Cardiac output increases
Rising blood pressure
Blood pressure rises
Stimulation of baroreceptors in
aortic arch and carotid sinuses
Baroreceptors in aortic arch and
carotid sinuses are stimulated
Sensory impulses to vasomotor center
Sensory impulses to cardiac center
Vasomotor center inhibited
Parasympathetic impulses to heart
Less frequent sympathetic impulses
to arteriole walls
SA node inhibited
Vasodilation of arterioles
Heart rate decreases
Decreased peripheral resistance
Blood pressure returns
toward normal 18
Blood pressure returns toward normal

19. Venous Blood Flow
Blood pressure decreases as the blood moves through the arterial system and into the capillary network, so little pressure remains at the venular ends of the capillaries
Only partly a direct result of heart action
Dependent on:
Skeletal muscle contraction
Breathing
Venoconstriction
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To heart
To heart
Relaxed skeletal
muscle
Vein
Valve open
Contracted
skeletal muscle
Vein
Valve closed 19

20. Central Venous Pressure
All veins, except those returning to the heart from the lungs, drain into the right atrium
This is therefore pressure in the right atrium
Factors that influence it alter flow of blood into the right atrium
It effects pressure within the peripheral veins
A weakly beating heart increases central venous pressure
An increase in central venous pressure causes blood to back up into the peripheral veins
This can lead to peripheral edema

21. 15.6: Paths of Circulation
Blood vessels can be divided into two major pathways:
The pulmonary circuit
The systemic circuit (includes coronary circulation)

22. Pulmonary Circuit 22 Right pulmonary artery Superior vena cava
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Right pulmonary artery
Superior
vena cava
Left pulmonary artery
Aorta
Pulmonary capillaries
Pulmonary capillaries
Right pulmonary veins
Left pulmonary veins
Pulmonary trunk
Left lung
Right lung
Inferior vena cava 22

23. of fluid from capillary
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Lymph flow
Blood flow
Blood flow
Lymphatic capillary
Alveolar capillary 1
Slight net outflow
of fluid from capillary 2
Solutes fail to enter
alveoli but contribute to
the osmotic pressure of
the interstitial fluid
Alveolar air 4
Fluid from the
interstitial space
enters lymphatic
capillary or alveolar
(blood) capillary
Capillary wall
Alveolar wall
Interstitial space 3
Any excess water in
alveolus is drawn out by
the higher osmotic pressure
of the interstitial fluid

24. Systemic Circuit
Composed of vessels that lead from the heart to all body parts (except the lungs) and back to the heart
Includes the aorta and its branches
Includes the system of veins that return blood to the right atrium

25. 15.7: Arterial System Superficial temporal a. External carotid a.
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Superficial temporal a.
External carotid a.
Internal carotid a.
Vertebral a.
Common carotid a.
Subclavian a.
Brachiocephalic a.
Axillary a.
Aorta
Coronary a.
Intercostal a.
Suprarenal a.
Celiac a.
Brachial a.
Superior mesenteric a.
Renal a.
Radial a.
Lumbar a.
Common iliac a.
Inferior mesenteric a.
Internal iliac a.
Gonadal a.
External iliac a.
Ulnar a.
Deep femoral a.
Femoral a.
Popliteal a.
Anterior tibial a.
Posterior tibial a.
Fibular a.
Dorsalis pedis a.

26. Principal Branches of the Aorta

27. Right internal jugular v.
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Right common carotid a.
Left common carotid a.
Right internal jugular v.
Right subclavian a.
Left internal jugular v.
Left subclavian a.
Brachiocephalic a.
Brachiocephalic vv.
Aortic arch
Superior vena cava
Ligamentum arteriosum
Left pulmonary a.
Right pulmonary a.
Left pulmonary vv.
Right pulmonary vv.
Left auricle
Right auricle
Pulmonary trunk

28. 15.8: Venous System Superficial temporal v. Anterior facial v.
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Superficial temporal v.
Anterior facial v.
External jugular v.
Internal jugular v.
Right brachiocephalic v.
Subclavian v.
Axillary v.
Superior vena cava
Cephalic v.
Azygos v.
Brachial vv.
Hepatic v.
Basilic v.
Inferior vena cava
Median cubital v.
Renal v.
Ascending lumbar v.
Radial vv.
Ulnar vv.
Gonadal v.
Common iliac v.
Internal iliac v.
External iliac v.
Femoral v.
Great saphenous v.
Popliteal v.
Posterior tibial vv.
Small saphenous v.
Anterior tibial vv.

29. Characteristics of Venous Pathways
Vessels of the venous system originate with the merging of capillaries into venules, venules into small veins, and small veins into larger ones
Unlike arterial pathways, those of the venous system are difficult to follow due to irregular networks and unnamed tributaries

30. Lower limb capillaries
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Head and upper
limb capillaries
Lungs
Deoxygenated blood
Oxygenated blood
Superior
vena cava
Aorta
Hepatic artery
Inferior
vena cava
Splenic artery
Hepatic vein
Hepatic
portal vein
Liver
Mesenteric artery
(to intestine)
Renal capillaries
Renal efferent
arterioles
Renal afferent
arterioles
Common
iliac vein
Trunk capillaries
Common
iliac artery
Lower limb capillaries

31. 15.9: Lifespan Changes Cholesterol deposition in the blood vessels
Heart enlargement
Death of cardiac muscle cells
Increase in fibrous connective tissue of the heart
Increase in adipose tissue of the heart
Increase in blood pressure
Decrease in resting heart rate