1. Chapter 13 Cardiovascular System
The heart pumps 7000 liters of blood through the body per day
Approximately 2.5 billion times in an average lifetime
Blood vessels
Arteries – large vessels that leave the heart & carry oxygen
Arterioles – smaller vessels that connect to arteries & carry oxygen
Capillaries – smallest blood vessels that move slowly and drop off nutrients, gases, and pick up waste
Venules – smaller vessels that are heading back to the heart
Veins – large vessels that enter the heart to pick up more oxygen at the lungs

2. Blood Vessel Circulation

3. Pulmonary & Systemic Circuits
The heart (pump) and blood vessels form the cardiovascular system
2 pathways for blood:
Pulmonary circuit
Sends oxygen depleted blood (deoxygenated) to the lungs to pick up oxygen and unload carbon dioxide
Systemic circuit
Sends oxygen-rich blood (oxygenated) and nutrients to all body cells and removes wastes
Without circulation, tissues would lack an oxygen and nutrient supply, and wastes would accumulate.

4. Structure of the Heart Hollow, cone-shaped, muscular pump
Found within the mediastinum
Lies within the thoracic cavity
Rests on the diaphragm
Average adult heart size is about
14 centimeters long
9 centimeters wide

5. Pericardium Encloses and surrounds the heart Fibrous pericardium
Outer bag made of dense connective tissue
Surrounds a more delicate double-layered sac
Visceral pericardium
Inner layer of double-layered sac
Also called epicardium
Covers the heart
Parietal pericardium
Inner lining of fibrous pericardium
Formed from visceral pericardium folding back on itself at the base of the heart
Pericardial cavity
Space between the parietal and visceral pericardium
Contains a small volume of fluid that reduces friction between the pericardial membranes as the heart moves

6. Structure of the Heart

7. Wall of the Heart 3 distinct layers Outer epicardium
Protects heart by reducing friction
Middle myocardium
Consists mainly of cardiac muscle tissue
Inner endocardium
Consists of many elastic and collagenous fibers
Contains blood vessels
Contains specialized cardiac muscle fibers called Purkinje fibers
Continuous with inner linings of blood vessels attached to the heart

8. Heart Chambers The heart is divided into 4 hollow chambers:
2 on the left and 2 on the right
2 upper chambers called atria (singular: atrium)
Have thin walls
Receive blood returning to the heart
Small, earlike projections called auricles extend anteriorly (mixing chambers)
2 lower chambers called ventricles
Receive blood from the atria
Contract to force blood into arteries

9. Heart Chambers
A solid, wall-like septum separates the atrium and ventricle on the right side from the atrium and ventricle on the left side
Blood from one side of the heart never mixes with blood on the other side
2 atrioventricular (A-V) valves ensure one way blood flow between the atria and the ventricles
Tricuspid valve on the right
Bicuspid or mitral valve on the left
The right atrium receives blood from 2 large veins
Superior vena cava
Inferior vena cava

10. Heart Valves (See Table 13.1, page 344)
Tricuspid Valve – (A-V Valve)
Located between the right atrium and right ventricle
Prevents blood flow from right ventricle into right atrium during ventricular contraction
Pulmonary Valve – (Semilunar Valve)
Located at entrance to pulmonary trunk
Prevents blood flow from pulmonary trunk into right ventricle during ventricular relaxation
Mitral (Bicuspid) Valve – (A-V Valve)
Located between left atrium and left ventricle
Prevents blood flow from left ventricle into left atrium during ventricular contraction
Aortic Valve – (Semilunar Valve)
Located at entrance to aorta
Prevents blood flow from aorta into left ventricle during ventricular relaxation

11. Heart Valves – Atrioventricular (A-V) Valves
Named atrioventricular valves because they are found between the atria and ventricles
Tricuspid valve
3 tapered projections called cusps
Permits blood to flow from right atrium to right ventricle
Strong fibrous strings called chordae tendineae attached to the cusps
Originate from papillary muscles
Prevent cusps from swinging back into the atrium
Ensures one way blood flow
Bicuspid or Mitral Valve
2 tapered projections called cusps
Shaped like a hat called a mitre
Permits blood flow from left atrium to left ventricle
Has chordae tendineae and papillary muscles

12. Mitral Valve Prolapse (MVP)
Affects up to 6% of the US population
One or both of the mitral valve cusps bulges into the left atrium during ventricular contraction
Blood may regurgitate into the left atrium
Through a stethoscope, a regurgitating sound may be heard and a murmur as blood backs into the left atrium
Symptoms: chest pain, palpitations, fatigue, anxiety
Damage may be caused by Streptococcus bacteria causing endocarditis (inflammation of endocardium)

13. Heart Valves – A-V Valves

14. Heart Valves

15. Heart Valves – Semilunar Valves
Named semilunar valves because of the half-moon shape of their cusps
Pulmonary Valve
3 cusps
Allows blood to leave the right ventricle
Prevents backflow into the ventricular chamber
Leads to the pulmonary trunk
Aortic Valve
Opens and allows blood to leave the left ventricle as it contracts
When ventricular muscles relax, closes and prevents blood from backing up into the ventricle

16. Heart Valves – Semilunar Valves

17. Path of Blood Through the Heart

18. Blood Supply to the Heart
Aorta (first 2 branches)
Coronary Arteries (left and right)
Supply blood to the tissues of the heart
3. Myocardial capillaries
Move slowly to drop off blood to all the cells of the heart
4. Cardiac veins
Drain blood that has passed through the myocardial capillaries
Paths roughly parallel the pathways of the coronary arteries
5. Coronary sinus
Enlarged vein on posterior
Empties into the right atrium

19. Heart Actions Systole means contraction of a heart chamber
Diastole means relaxation of a heart chamber
Chambers function in a coordinated fashion
When atria contract (atrial systole) the ventricles relax (ventricular diastole)
When the ventricles contract (ventricular systole) the atria relax (atrial diastole)
The series of events that constitutes a complete heartbeat is called the cardiac cycle.

20. Heart Actions Bradycardia An abnormally slow heart rate
Less than 50 beats per minute
Tachycardia
An abnormally fast heart rate
Greater than 100 beats per minute.

21. Cardiac Cycle During the cardiac cycle
The pressures within the heart chambers rise and fall
This allows the valves to open and close (like doors being blown open or closed by the wind)
When the pressure in the ventricles is low, it causes the A-V valves to open and the ventricles to fill
About 70% of the returning blood enters the ventricles prior to contraction
When the atria contract, the remaining 30% of returning blood is pushed into the ventricles.

22. Cardiac Cycle As the ventricles contract
Ventricular pressure rises sharply
As soon as the ventricular pressure exceeds the atrial pressure, the A-V valves close
Papillary muscles contract and pull on the chordae tendineae
Prevents the cusps of the A-V valves from bulging into atria
A-V valves remain closed during ventricular contraction
Atria are now relaxed
Pressure in the atria is low
Blood flows into the atria from the large attached veins

23. Cardiac Cycle
When ventricular pressure exceeds the pressure in the pulmonary trunk (on the right side) and the aorta (on the left side) the pulmonary and aortic valves open
Blood is ejected from the ventricles into these arteries
As blood flows out of the ventricles, ventricular pressure drops and the ventricles relax
When ventricular pressure is lower than the pressure in the pulmonary trunk and aorta, the semilunar valves close
When ventricular pressure is lower than the pressure in the atria, the A-V valves open and ventricles begin to fill
This sequence repeats for each cycle

24. Heart Sounds
Through a stethoscope, the heartbeat sounds like lubb-dupp
The sounds are due to the vibrations in the heart tissues as the valves close
Lubb
First heart sound
During ventricular contraction
A-V valves are closing
Dupp
Second heart sound
During ventricular relaxation
Semilunar valves are closing

25. Electrocardiogram (ECG or EKG)
Recording of electrical changes that occur in the myocardium during a cardiac cycle
Normal ECG pattern includes several deflections, or waves during each cycle
Between cycles, the muscle fibers remain polarized
No detectable electrical changes
Pen does not move but marks along the baseline
Physicians use ECG patterns to assess the heart’s ability to conduct impulses

26. Blood Vessels (See Figure 13.2, page 358)
Form a closed circuit of tubes that carry blood from the heart to body cells and back to the heart again.
Vasoconstriction – smooth muscles contract and diameter of vessel is reduced
Vasodilation – smooth muscles relax and diameter of vessel is increased.
Arteries
Strong, elastic vessels
Carry blood away from the heart under high pressure
Weakness in the wall causes a bulging area called an aneurysm
If an aneurysm ruptures, it may produce a great loss of blood

27. Blood Vessels (continued)
Arterioles
Thinner, finer, branched vessels that connect to arteries and capillaries
Capillaries
Smallest-diameter blood vessels
Connect smallest arterioles to the smallest venules
Move blood slowly so that nutrients and gases may diffuse into cells
Venules
Microscopic vessels that continue from the capillaries and merge to form veins
Veins
Carry blood back to the heart
Serve as blood reservoirs
Contain valves to help push blood back to the heart

28. Blood Vessels (continued)

29. Blood Pressure (BP)
The force blood exerts against the inner walls of blood vessels
Most commonly refers to pressure in the arteries supplied by the aorta
Rises and falls in a pattern that corresponds to the phases of the cardiac cycle
Systolic pressure
Maximum pressure on arteries
Occurs during ventricular contraction
Diastolic pressure
Lowest pressure that remains in arteries before the next ventricular contraction
Sphygmomanometer
Instrument used to measure arterial BP

30. Blood Pressure Units: mmHg = millimeters of mercury
Blood Pressure expressed as a fraction
Upper number: Systolic pressure
Lower number: Diastolic pressure

31. Factors that Influence Blood Pressure
Heart action
Determines how much blood enters the arterial system with each ventricular contraction
The volume of blood discharged with each ventricular contraction is called stroke volume
About 70 milliliters in an average male at rest
Blood volume
Equals the sum of the formed elements and plasma volumes in the vascular system
About 8% of body weight or 5 liters for adults
Peripheral resistance
Friction between the blood and the walls of blood vessels
Hinders blood flow
Blood viscosity
The ease with which a fluid’s molecules flow past one another
The greater the viscosity, the greater the resistance to flow
Blood cells and plasma proteins increase viscosity

32. Factors that Influence Blood Pressure

33. Paths of Circulation Two major pathways Pulmonary circuit
Consists of vessels that carry blood from the heart to the lungs and back to the heart
Includes the pulmonary arteries, lungs, and pulmonary veins.
Systemic circuit
Consists of vessels that carry blood from the heart to all other parts of the body and back again
Includes the aorta and its branches that lead to all body tissues and the vena cavae