1. Chapter 12 The Heart

2. Location, Size, and Position of the Heart
In mediastinum
2/3 to the left of the body midline
Apex = point
Most inferior portion
Shape and size of a closed fist
Septum divides right and left sides
(internally)
Apex is on the diaphragm

3. Pericardium Two-layered fibrous sac
Inner layer = visceral pericardium or epicardium
Outer layer = parietal pericardium
Pericardial cavity is filled with pericardial fluid
Approximately ml pericardial fluid present
The pericardium and pericarditis
Pericardium is a two-layered fibrous sac with a lubricated space between the two layers
Inner layer is called visceral pericardium or epicardium
Outer layer called parietal pericardium
What is the condition for inflammation of the pericardium? Pericarditis
Why is this condition serious?

4. Three layers of the Heart Wall
Epicardium
Outer layer
Connective tissue
Myocardium
Middle layer
Thick
Muscle
Endocardium
Inner layer (lining)
Very thin, smooth

5. Summary of layers Outside (external) to Inside (internal)
Parietal Pericardium
Pericardial cavity (filled with fluid)
Visceral Pericardium/Epicardium
Myocardium
Endocardium
Wall of each heart chamber is composed of cardiac muscle tissue called myocardium
Endocardium—smooth lining of heart chambers—inflammation of endocardium called endocarditis

6. Anatomy of the Heart Heart chambers Two upper chambers are
Right and left atria (atrium)
Small chambers
Receive blood
Two lower chambers called ventricles
Right and left ventricles
Larger chambers
Pump blood out of heart

7. Vessels Pulmonary Arteries Pulmonary Veins
Carry blood from R ventricle to lungs
R pulmonary artery to R lung
L pulmonary artery to L lung
Pulmonary Veins
Carry blood from lungs to L atria
R pulmonary veins from R lung
L pulmonary veins from L lung

8. Vessels cont. Vena Cava Inferior and superior
Empties blood into heart from body

9. Valves Cuspid valves Semilunar valves
Tricuspid: between right atrium and ventricle
Bicuspid (mitral): between left atrium and ventricle
Open and close from chordae tendineae
Semilunar valves
Pulmonary Semilunar: base of pulmonary arteries
Aortic Semilunar: base of aorta
Open and close from pressure within heart
Four valves keep blood flowing through the heart; prevent backflow (two atrioventricular or AV and two semilunar valves)
Tricuspid: at the opening of the right atrium into the ventricle
Bicuspid (mitral): at the opening of the left atrium into the ventricle
Incompetent valves “leak,” allowing some blood back into the chamber from which it came
Stenosed valves are narrower that normal, reducing blood flow
Rheumatic heart disease—cardiac damage resulting from a delayed inflammatory response to streptococcal infection
Mitral valve prolapse (MVP)—incompetence of mitral valve because its edges extend into the left atrium when the left ventricle contracts

10. The 4 valves

11. The heart is where pulmonary circulation starts and ends.
The valves support 1-way movement through the heart.

12. The heart acts as two pumps
Right atrium and ventricle pump deoxygenated blood to the lungs
Left atrium and ventricle pump oxygenated blood to the body

13. Sequence of Blood Flow
Venous blood enters the right atrium through the superior and inferior vena cava -- passes from the right atrium through the tricuspid valve to the right ventricle; from the right ventricle through the pulmonary semilunar valve to the pulmonary artery to the lunges – blood from the lungs to the left atrium, passing through the bicuspid (mitral) valve to the left ventricle; blood in the left ventricle is pumped through the aortic semilunar valve into the aorta and is distributed to the body as a whole.

14. Heart Sounds
Two distinct heart sounds in every heartbeat or cycle—“lubb-dupp”
First (lubb) sound is caused by the vibration and closure of AV valves during contraction of the ventricles
Second (dupp) sound is caused by the closure of the semilunar valves during relaxation of the ventricles

15. Heart Actions Contraction is called systole
Relaxation is called diastole
These actions create Blood Pressure
What does blood pressure measure?
Why is it important to monitor blood pressure?
What is an ideal BP?

16. Practical Application
Supposed an individual was injured by falling off a roof and he severely damaged his right arm with copious blood loss. His blood pressure steadily dropped to dangerous levels. How would you explain the drop in his blood pressure?
A basic principle of physics states that a decrease in fluid volume in a closed container causes a drop in the pressure with which that fluid is pushing on the sides of that container. Thus, loss of blood (decrease in blood volume) from the blood vessels (a closed network of tubes) decreases the overall pressure of blood in the vessels.

17. Continued
In response to the drop in blood pressure, the heart begins beating more rapidly. The increase in HR increases overall blood flow and thus causes even more rapid blood loss from a wound. The more blood lost, the faster the heart beats and the faster blood volume is lost. How can you explain this? What type of feedback is this?
This is a positive feedback response because the response, an increase in heart rate and thus an increase in blood flow, actually moves you farther away from the normal range of blood pressure (it amplifies the change rather than reversing the change). A negative feedback response would have restored BP to normal.
Does this response (increase in HR) tend to restore homeostatic balance or does it tend to create an imbalance?
This response tends not only to create an imbalance, it actually makes an existing imbalance worse (the classic hallmark of a positive feedback response). The BP continues to fall, rather than rise back toward normal.

18. Cardiac Cycle
Heart beat is regular and rhythmic—each complete beat called a cardiac cycle—average is about 72 beats per minute
Each cycle, about 0.8 seconds long, subdivided into systole (contraction phase) and diastole (relaxation phase)

19. Cardiac Cycle
Stroke volume is the volume of blood ejected from one ventricle with each beat
Cardiac output is amount of blood that one ventricle can pump each minute—average is about 5 L per minute at rest
Benefit of exercise!

20. Conduction System of the Heart
SA (sinoatrial) node
The pacemaker
In wall of right atrium near superior vena cava
AV (atrioventricular) node
In the floor of right atrium near septum
AV bundle (bundle of His)
Located in the septum of the ventricle
Purkinje fibers—
Located in the walls of the ventricles
Cause contraction of myocardium

22. Conduction System of the Heart
Electrocardiography
Measures the electrical impulses that result in contraction of the heart
Impulses transformed into visible tracings by a machine called an electrocardiograph
The visible tracing of these electrical signals is called an electrocardiogram or ECG

23. Conduction System of the Heart
The normal ECG has three deflections or waves called the P wave, the QRS complex, and the T wave
P wave—associated with depolarization of the atria
QRS complex—associated with depolarization of the ventricles
T wave—associated with repolarization of the ventricles

24. Issues with the heart’s conduction system
Bradycardia—slow heart rate (under 60 beats/min)
Tachycardia—rapid heart rate (over 100 beats/min)
Sinus dysrhythmia—variation in heart rate during breathing cycle
Premature contraction (extrasystole)—contraction that occurs sooner than expected in a normal rhythm
Fibrillation—condition in which cardiac muscle fibers are “out of step,” producing no effective pumping action

25. Chronic diseases of the heart

26. Coronary Circulation and Coronary Heart Disease
Blood, which supplies oxygen and nutrients to the myocardium of the heart, flows through the right and left coronary arteries
Blockage of blood flow through the coronary arteries can cause myocardial infarction

27. CHD
Atherosclerosis (type of “hardening of arteries” in which lipids build up on the inside wall of blood vessels) can partially or totally block coronary blood flow
Angina pectoris—chest pain caused by inadequate oxygen to the heart

28. Heart Failure
Heart failure—inability to pump enough returned blood to sustain life; it can be caused by many different heart diseases
Right-sided heart failure—failure of the right side of the heart to pump blood, usually because the left side of the heart is not pumping effectively

29. Heart Failure
Left-sided heart failure (congestive heart failure)—inability of the left ventricle to pump effectively, resulting in congestion of the systemic and pulmonary circulations
Diseased hearts can be replaced by donated living hearts (transplants) or by artificial hearts (implants), although both procedures have yet to be perfected