1. Cardiovascular System
Chapter 13
Cardiovascular System
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2. Animation: Baroreceptor Reflex Control of Blood Pressure
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3. Regulation of the Cardiac Cycle
The SA node controls the heart rate
There are also sympathetic and parasympathetic fibers that control the heart rate as well
There are also regulatory reflex centers that influence heart rate
Additional factors that may influence heart rate include:
Physical exercise
Body temperature
Concentration of various ions including:
Potassium
Calcium
Parasympathetic impulses via vagus nerve decrease heart action
Sympathetic impulses via accelerator nerve increase heart action
Cardiac center regulates autonomic impulses to the heart

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

5. 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)
Some smooth muscle tissue
Small amount of connective tissue
Helps control blood flow into a capillary through action of precapillary sphincters
Both arteries and arterioles can undergo vasoconstriction and vasodilation.

6. (elastic and collagenous fibers)
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)

7. Arteriole Smooth muscle cell Endothelium Precapillary sphincter7

8. 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
Metarteriole (forming arteriovenous
shunt)
Precapillary
sphincter
Arteriole
Capillaries
Venule
Artery
Vein
Blood flow
Blood flow

9. Arteriole
Capillary
Venule

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

12. Blood Pressure
Blood pressure is the force the blood exerts against the inner walls of the blood vessels
Most commonly refers to pressure in systemic arteries

13. 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

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

15. 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
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

16. 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
Blood pressure returns toward normal 16

17. 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 movements
Venoconstriction
To heart
To heart
Relaxed skeletal
muscle
Vein
Valve open
Contracted
skeletal muscle
Vein
Valve closed 17

18. 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 (central venous pressure)
Factors that influence it alter flow of blood into the right atrium
It affects 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

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

20. Pulmonary Circuit 20 Systemic capillaries Tissue cells CO2 O2 Superior
vena cava
Pulmonary
artery
Alveolus
CO2
CO2
Alveolar
capillaries
Alveolar
capillaries O2 O2
Alveolus
Pulmonary
veins
Right atrium
Left atrium
Tricuspid valve
Mitral valve
Pulmonary valve
Left ventricle
Right ventricle
Aortic valve
Inferior vena cava
Aorta O2
CO2
Systemic
capillaries 20
Tissue cells

21. 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

22. Arterial System 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.

23. Principal Branches of the Aorta

24. Arteries to the Brain, Head, and Neck
Superficial
temporal a.
Posterior
auricular a.
Anterior choroid a.
Basilar a.
Occipital a.
Maxillary a.
Internal
carotid a.
Facial a.
Lingual a.
External
carotid a.
Superior thyroid a.
Common carotid a.
Carotid sinus
Brachiocephalic a.
Vertebral a.
Thyrocervical
axis
Subclavian a.

25. Arteries to the Brain, Head, and Neck
Anterior
communicating a.
Anterior
cerebral a.
Anterior
cerebral a.
Middle
cerebral a.
Internal
carotid a.
Posterior
communicating a.
Pituitary
gland
Middle
cerebral a.
Posterior
cerebral a.
Basilar a.
Basilar a.
Vertebral a.
Spinal a.
Spinal cord

26. Arteries to the Shoulder and Upper Limb
Right common carotid a.
Right subclavian a.
Axillary a.
Anterior circumflex a.
Posterior circumflex a.
Deep brachial a.
Brachial a.
Radial recurrent a.
Ulnar recurrent a.
Radial a.
Ulnar a.
Principal
artery of
thumb
Deep volar arch a.
Superficial volar arch a.
Digital a.

27. Arteries to the Thoracic and Abdominal Walls
Vertebral body
Posterior intercostal a.
Internal intercostal m.
Thoracic aorta
Internal thoracic a.
External intercostal m.
Sternum
Anterior intercostal aa.
Costal cartilage

28. Arteries to the Pelvis 28 Aorta Inferior mesenteric a.
Left common iliac a.
Inferior epigastric a.
Right common iliac a.
Middle sacral a.
Internal iliac a.
Iliolumbar a.
External iliac a.
Superior gluteal a.
Deep
circumflex iliac a.
Lateral sacral a.
Inferior gluteal a.
Femoral a.
Internal pudendal a.
Obturator a.
Inferior vesical a.
Superior vesical a.
Perineal a.
Inferior rectal a. 28

29. Arteries to the Lower Limb
Right common iliac a.
Abdominal
aorta
Deep circumflex iliac a.
External iliac a.
Internal iliac a.
Superficial circumflex iliac a.
Superficial
pudendal a.
Deep femoral a.
Femoral a.
Lateral femoral a.
Deep genicular a.
Popliteal a.
Anterior tibial a.
Posterior tibial a.
Fibular a.
Dorsalis pedis a.
Lateral plantar a.
Medial plantar a.
Anterior view
Posterior view 29

30. Venous System 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.

31. 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

32. Veins from the Brain, Head, and Neck
Venous
sinuses
Superior
ophthalmic v.
Vertebral v.
Right external
jugular v.
Right
Subclavian v.
Anterior
facial v.
Right internal
jugular v.
Right axillary v.
Right brachiocephalic v.

33. Veins from the Upper Limb and Shoulder
Right internal jugular v.
Right external jugular v.
Right subclavian v.
Left brachiocephalic v.
Right brachiocephalic v.
Axillary v.
Superior vena cava
Brachial vv.
Cephalic v.
Basilic v.
Median cubital v.
Radial vv.
Ulnar vv.
Dorsal arch v.

34. Veins from the Abdominal and Thoracic Walls
Internal jugular v.
External jugular v.
Brachiocephalic vv.
Subclavian v.
Superior vena cava
Cephalic v.
Superior hemiazygos v.
Axillary v.
Posterior intercostal v.
Brachial v.
Basilic v.
Azygos v.
Inferior hemiazygos v.

35. Veins from the Abdominal Viscera
Liver
Stomach
Hepatic
portal v.
Left gastric v.
Right gastric v.
Gallbladder
Spleen
Pancreas
Splenic v.
Superior
mesenteric v.
Inferior
mesenteric v.
Portion of
small intestine
Ascending colon
Descending colon
Rectum

36. Veins from the Lower Limb and Pelvis
Inferior
vena cava
Right common
iliac v.
External iliac v.
Internal
iliac v
Femoral v.
Great saphenous v.
Popliteal v.
Anterior tibial vv.
Small saphenous v.
Fibular vv.
Posterior tibial vv
Medial plantar vv.
Dorsalis pedis v.
Lateral plantar vv.
Anterior view
Posterior view

37. Lifespan Changes Cholesterol deposition in the blood vessels
Heart enlargement
Proportion of cardiac muscle cells declines
Increase in fibrous connective tissue of the heart
Increase in adipose tissue of the heart
Increase in blood pressure
Decrease in resting heart rate
Lumens of large arteries narrow
Decrease in arterial elasticity