1. 15.4: Blood Pressure Blood pressure:
The force the blood exerts against the inner walls of the blood vessels
Blood pressure circulates the blood
The term “blood pressure” most commonly refers to pressure in systemic arteries
There is blood pressure throughout the vascular system
Blood moves from higher to lower pressure throughout the system

2. Arterial Blood Pressure
Rises when the ventricles contract
Falls when the ventricles relax
Systolic pressure (SP): the maximum pressure reached during ventricular contraction
Diastolic pressure (DP): the minimum pressure remaining before next ventricular contraction
Pulse pressure (PP): difference between systolic and diastolic blood pressures (SP – DP)
Mean arterial pressure (MAP): Average pressure in arterial system; represents average force driving blood to the tissues (DP + 1/3 PP)
Blood pressure is stated as a fraction: SP/DP, as in 120/80
Blood pressure is stated in units of mm Hg

3. Factors That Influence Arterial Blood Pressure

4. Blood Volume Blood Volume:
Sum of volumes of plasma and formed elements
Varies with age, body size, gender
Usually about 5 L for adults
8% of body weight
Blood pressure (BP) is directly proportional to blood volume
Any factor that changes blood volume can change BP
Example: Decreased blood volume, due to hemorrhage, decreases BP

5. Viscosity
Viscosity:
Difficulty with which molecules of fluid flow past each other
Greater the viscosity, the greater the resistance to blood flow
Blood cells and plasma proteins increase the viscosity of the blood
Greater the resistance to flow  greater the force necessary to transport the blood  greater the blood pressure becomes
Any factor that alters concentration of blood cells or plasma proteins also alters blood viscosity
Example: Anemia lowers concentration of blood cells  lowers blood viscosity  lowers the blood pressure

7. Clinical Application 15.3 Hypertension
Hypertension (high blood pressure):
Long-lasting elevated arterial blood pressure
Causes: unknown cause, increased Na+ intake, psychological stress that activates the sympathetic nervous system, obesity (by increasing the peripheral resistance), kidney disease (via renin-angiotensin response)
“Silent killer,” because it may not cause any direct symptoms
Contributes to formation of atherosclerosis
May lead to coronary thrombosis or embolism
May lead to cerebral thrombosis, embolism, or hemorrhage, perhaps resulting in a transient ischemic attack (TIA, ministroke) or a cerebral vascular accident (CVA, stroke)
Prevention: healthy diet and weight, regular exercise, limiting Na+ intake
Treatments: diuretics, sympathetic inhibitors

8. 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 venous ends of the capillaries
Venous Blood Flow:
Only partly a direct result of heart action
Also dependent on:
Skeletal muscle contraction
Breathing movements
Vasoconstriction of veins

9. Exercise and the Cardiovascular System
Clinical Application 15.4
Exercise and the Cardiovascular System
Exercise is good for heart, but it has to be regular part of life. Cardiovascular system adapts to aerobic exercise:
Increased pumping efficiency, blood volume, hemoglobin concentration,
number of mitochondria
Heart may enlarge 40% or more
Stroke volume increases
Heart rate and blood pressure decrease
For exercise to benefit cardiovascular system:
Heart rate must increase to 70-85% of maximum (220 – your age)
Must last minutes
At least 3-4 times/week

10. 15.5: Paths of Circulation Blood vessels form 2 pathways:
The pulmonary circuit
The systemic circuit

11. Pulmonary & Systemic Circuits
Pulmonary circuit:
Right ventricle  pulmonary trunk  right and left pulmonary arteries  lobar branches, repeated divisions  pulmonary arterioles  pulmonary capillaries  pulmonary venules and veins  left atrium
Blood in pulmonary arteries and arterioles is low in O2 and high in CO2
Gas exchange occurs in pulmonary (alveolar) capillaries
Blood in pulmonary venules and veins is rich in O2 and low in CO2
Systemic circuit:
Oxygen-rich blood moves from left atrium to left ventricle
Contraction of left ventricle sends blood into systemic circuit
Left ventricle  aorta  all arteries and arterioles leading to body tissues  systemic capillaries  systemic venules and veins  right atrium

12. Alveolar Wall and Osmosis
High osmotic pressure in interstitial fluid draws water out of alveoli.

13. 15.6: Arterial System
The aorta is the largest artery in the body. It supplies blood to all of the systemic arteries.

14. Major Branches of the Aorta

15. Major Vessels Associated With the Heart

16. Major Branches of the Abdominal Aorta

17. Arteries to the Brain, Head and Neck
Branches of the subclavian and common carotid arteries supply blood to brain, head and neck.

18. Arteries to the Brain, Head and Neck
The cerebral arterial circle (circle of Willis) joins the carotid and vertebral artery systems. These arteries supply blood to the brain; the arrangement provides alternate pathways for blood to reach the brain. The cerebral arteries emerge from the circle to supply blood to brain tissues.

19. Arteries to the Shoulder and Upper Limb
The subclavian artery gives off branches in the neck, and then continues into the arm.

20. Arteries to the Thoracic and Abdominal Walls
Blood reaches the thoracic wall via branches of several vessels, including the subclavian artery and the thoracic aorta.

21. Arteries to the Pelvis
The abdominal aorta divides into the common iliac arteries, which supply blood to the pelvic organs, gluteal region, and lower limbs. The common iliac artery divides into the internal iliac artery and external iliac artery. The internal iliac artery supplies blood to the pelvic and gluteal areas.

22. Arteries to the Lower Limb
The external iliac arteries provide the major blood supply to the lower limbs.

23. 15.7: Venous System

24. Characteristics of Venous Pathways
Systemic venous circulation returns blood to heart after exchange of gases, nutrients, and wastes between blood and cells
Vessels of the venous system originate from 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
Pathways of larger veins usually parallel arteries of the same name
All systemic veins converge into the superior and inferior venae cavae, and return to the heart through the right atrium

25. Veins From the Brain, Head and Neck
The external jugular veins drain blood from the face, scalp, and superficial neck. The internal jugular from the brain, and deep portions of the face and neck.

26. Veins From the Upper Limb and Shoulder
2 systems of veins drain the upper limb and shoulder: Deep set of veins: Digital veins  radial and ulnar veins  brachial veins Superficial set of veins: Anastomoses in palm and wrist  basilic and cephalic veins. Basilic vein joins brachial vein, and cephalic vein joins axillary vein.

27. Veins From the Abdominal and Thoracic Walls
The abdominal and thoracic walls are drained by tributaries of the brachiocephalic and azygos veins. The azygos vein drains directly into the superior vena cava.

28. Veins From the Abdominal Viscera
Portal veins are unusual, in that they do not transport blood directly to the heart. The abdominal viscera are drained by a unique venous pathway, called the hepatic portal system. Blood from capillaries in the stomach, intestines, pancreas, and spleen drain into the hepatic portal vein, which transports it to the liver for processing, before it is delivered to inferior vena cava.

29. Portal systems, such as the Hepatic Portal System and the Renal Portal System, filter blood through 2 sets of capillaries, instead of the usual 1 set. This second set of capillaries performs a unique function in the body.

30. Veins From the Lower Limb and Pelvis
Blood from lower limb drains into deep and superficial groups of veins: Deep set of veins: Veins in foot  anterior and posterior tibial veins  popliteal vein  femoral vein  external iliac vein Superficial set of veins: Veins in foot  small and great saphenous veins. Great saphenous vein is the longest vein in the body.

31. 15.8: Life-Span Changes Cholesterol deposition in the blood vessels
Narrowed coronary arteries
Heart may shrink slightly, or enlarge due to disease
Proportion of heart consisting of cardiac muscle declines
Increase in fibrous connective tissue of the heart
Increase in adipose tissue of the heart
Heart valves and left ventricular wall may thicken
Increase in systolic blood pressure
Decrease in resting heart rate
Lumens of large arteries narrow, as arterial walls thicken
Decrease in arterial elasticity