1. Anatomy Ch. 11
The Heart

2. Size, Location, and Orientation
Size of a person’s fist
Hollow
Cone shaped
Weighs less than a pound
Enclosed within the mediastinum
Flanked on each side by the lungs
Pointed apex is directed toward the left hip and rests on the diaphragm
The base is at the top and is the location where the great vessels of the body emerge.
The base points toward the right shoulder

3. Coverings and Walls of the Heart
Pericardium: double layered sac that encloses the heart
Fibrous pericardium: outer part of the sac that protects the heart and anchors it to surrounding structures
Serous pericardium: found inside the fibrous layer and has two layers (parietal and visceral)

4. Parietal Visceral Serous fluid Outer layer
Folds inward and covers the heart surface as the visceral layer
Visceral
Also called the epicardium which is actually part of the heart wall
Serous fluid
Found between the parietal and visceral layers
Allows the heart to beat easily and smoothly

5. The heart wall is composed of 3 layers
Epicardium
Outer layer
Myocardium
Middle layer
Contains cardiac muscle
Layer that actually contracts
Contains a tissue layer that is sometimes called the “skeleton of the heart”
Endocardium
Lines the heart chambers
Continuous with the lining of the blood vessels that enter and leave the heart

6. Chambers and Associated Great Vessels
The heart has 4 hollow chambers:
Atria (2)
Superior
Receiving chambers
Not important in pumping activity of the heart
Blood flows into the atria under low pressure and then continues on to fill the ventricles
The 2 atria are separated by an interatrial septum

7. Ventricles(2)
Inferior
Thicker walls than the atria
Discharging chambers which actually pump blood out of the heart and into circulation
The 2 ventricles are separated by an interventricular septum
Each of these 4 chambers is lined with endocardium which helps blood flow smoothly.

8. Right side of the heart Pulmonary circulation
Receives oxygen poor blood from the body through the superior and inferior vena cava
Pumps the oxygen poor blood to the lungs through the pulmonary arteries where gas exchange occurs (CO2 and wastes out of the blood and oxygen into the blood)
Oxygen rich blood is returned to the left side of the heart through the pulmonary veins.
Only function is gas exchange in the lungs

9. Left side of the heart Systemic circulation
Receives oxygen rich blood from the lungs
Pumps the oxygen rich blood to the organs of the body (aorta)
Gas and nutrient exchange in the organs of the body (oxygen to organs, CO2 and wastes to blood)
Oxygen poor blood is returned to the right side of the heart through the superior and inferior vena cava

10. Heart Valves The heart has 4 valves
The valves allow blood to flow in one direction through the chambers of the heart.
The atrioventricular valves (AV valves) are located between the atria and ventricles on each side of the heart
The AV valves prevent backflow into the atria when the ventricles contract
The left AV valve is called the bicuspid or mitral valve
The right AV valve is called the tricuspid valve

11. Chordae tendinae are tiny white cords that anchor the flaps of the AV valves to the walls of the ventricles.
Blood enters the ventricles when the heart is relaxed and the flaps of the AV valves hang limply.
When the ventricles contract the pressure inside the ventricles rises which forces the AV valves to close.
The chordae tendinae keep the AV valves closed and the flaps from moving upward into the atria.

12. The semilunar valves guard the bases of the 2 large arteries that leave the ventricles
Each valve has 3 leaflets.
When the ventricles contract, blood is forced through the valves which flatten against the walls of the large arteries.
When the ventricles relax the valves close because the leaflets of the valves fill with blood. This prevents back flow from the arteries into the ventricles

13. Each set of valves operates at a different time.
The AV valves are open when the heart is relaxed and closed when the heart contracts.
The semilunar valves are closed when the heart is relaxed and open when the heart contracts.
The valves open and close in response to pressure changes.
The valves ensure that blood flows in one direction.

14. Cardiac Circulation
The blood supply that oxygenates and nourishes the heart is provided by the left and right coronary arteries.
The layer of the heart that is nourished is the myocardium
The coronary arteries branch from the base of the aorta
The coronary arteries encircle the heart in the coronary sulcus which is found at the junction of the atria and ventricles.

15. The major branches of the coronary arteries:
Left: anterior interventricular artery and circumflex artery
Right: posterior interventricular artery and marginal artery
The coronary arteries and branches are compressed when the ventricles contract and fill when the heart is relaxed.

16. The myocardium is drained by the cardiac veins which empty into a large vessel called the coronary sinus.
The coronary sinus empties into the right atrium.

17. Physiology of the Heart
Cardiac muscle cells contract spontaneously and independently.
The contractions occur in a regular and continuous way.
Cardiac muscle cells in different areas of the heart have different rhythms.
Atrial cells: 60 times per minute
Ventricular cells: 20 – 40 times per minute

18. Two system act to regulate heart activity
Autonomic nervous system
Increases or decreases heart rate depending on which division is activated
Intrinsic conduction system (nodal system)
Built into the heart tissue and sets the rhythm
Contains a special tissue that is not found anywhere else in the body. This tissue is like a cross between muscle and nervous tissue.
Causes heart muscle depolarization in only one direction – atria to ventricles.
Ensures that the heart beats as a coordinated unit.

19. Components of the intrinsic conduction system
Sinoatrial (SA) node
Right atrium
Tiny cell mass
Highest rate of depolarization
Starts each heart beat and sets the pace for the whole heart
The pacemaker

20. Atrioventricular (AV) node
Junction of the atria and ventricles
Receives the impulse from the SA node
Cause the atria to contract
A delay occurs at this node to allow for complete contraction of the atria

21. Atrioventricular (AV) bundle (bundle of His) Bundle branches
Interventricular septum
Purkinje fibers
Spread out in muscle of ventricle walls
Impulses pass rapidly through the AV bundle, bundle branches, and purkinje fibers
Contraction of the ventricles begins at the apex and moves toward the atria.
This type of contraction ejects blood toward the large arteries that leave the heart.

22. The Cardiac Cycle and Heart Sounds
The atria contract simultaneously
As the atria relax the ventricles contract
Systole: ventricle contraction
Diastole: ventricle relaxation
Cardiac cycle: events of one complete heart beat
Avg. BPM: 75, Length of one cardiac cycle: 0.8 secs.

23. 3 periods of the cardiac cycle
Mid to late diastole
Heart in complete relaxation
Pressure is low
Blood flows passively through the atria into the ventricles
AV valves are open, semilunar valves are closed
Atria contract and force any remaining blood into the ventricles

24. Ventricular systole
Pressure in the ventricles increases rapidly closing the AV valves
When the pressure in the ventricles is higher than in the large vessels, the semilunar valves are forced open
Blood rushes out of the ventricles and into the large vessels
The atria are relaxed and filling with blood

25. Early diastole
Ventricles relax and semilunar valves snap shut which prevents backflow
Interventricular pressure drops below pressure in the atria
The AV valves are forced open
Ventricles begin to refill rapidly with blood

26. During each cardiac cycle there are 2 heart sounds called “lub” and “dup”
“lub”: the first sound caused by the closing of the AV valves
“dup”: the second heart sound caused by the closing of the semilunar valves

27. Cardiac output (CO)
CO is the amount of blood pumped out by each ventricle in 1 minute.
CO is the product of heart rate (HR) and stroke volume (SV)
SV is the volume of blood pumped out by a ventricle with each heart beat (70 mL)
Stroke volume increases as the force of the ventricular contraction increases.
Because the normal adult blood volume is about 6000 mL, the entire blood supply passes through the body once each minute.

28. Regulation of Stroke Volume
The critical factor controlling SV is how much the cardiac muscles are stretched just before they contract.
The more the muscle cells stretch the stronger the contraction will be.
The important factor stretching the heart is the amount of blood entering the heart.

29. If one side of the heart begins to pump more blood than the other, the increased return to the other ventricle will force it to pump out an equal amount.
This prevents a backup of blood in circulation
Anything that increases the volume or speed of blood return will increase stroke volume and contraction force and vice versa.

30. Factors moderating heart rate
Autonomic Nervous System
Sympathetic division stimulates SA and AV nodes causing the heart to beat more rapidly
Parasympathetic division uses the vagus nerve slows and steadies the heart
Chemicals that affect heart rate
Hormones: epinepherine (fight or flight) and thyroxine (metabolism)
Ions: calcium, sodium, and potassium

31. Physical factors Age: heart rate decreases throughout life
Gender: on average heart rate is faster in females
Heat increases heart rate and cold decreases heart rate
Exercise increases heart rate

32. Electrocardiograms (ECG)
Flow of electrical current through the heart
3 waves
P wave
Small wave
Depolarization of atria before contraction
QRS wave
Large complex
Depolarization of ventricles
Precedes contraction of ventricles
T wave
Repolarization of ventricles

33. Homeostatic Imbalances of the Heart
Pericarditis
Inflammation of the pericardium
The layers bind and stick forming painful adhesions
Endocarditis
Bacterial infections of the endocardium
Valvular stenosis
Valve flaps of the heart become stiff
The heart has to pump more vigorously

34. Incompetent valve Deformed valve
The heart has to repump the same blood because the valve does not close properly causing blood to backflow
Valves are replaced by a synthetic valve, a cryopreserved human valve, or a treated valve from a pig heart

35. Angina pectoris (choked chest)
Occurs when the myocardium is deprived of oxygen
Severe chest pain
If angina is prolonged then heart cells my die forming an infarct.
Myocardial infarction
A heart attack or coronary

37. Heart block Ischemia Caused by damage to the AV node
The ventricles are no longer under the control of the SA node
The ventricles begin to beat at their own rate which is much slower.
Ischemia
Lack of adequate blood supply to the heart

38. Fibrillation Rapid uncoordinated shuddering of the heart muscle
Makes the heart totally useless as a pump
Major cause of death from heart attacks in adults.

39. Heart Murmurs Abnormal or unusual heart sounds
Occurs when blood is obstructed
Can be heard with a stethoscope
Common in young children some elderly people.
Due to thin heart walls that vibrate
In other age groups, the murmur is usually caused by valve problems.

40. Congestive Heart Failure
Pumping efficiency of the heart decreases
Circulation is inadequate to meet tissue needs
Progressive condition that reflects the weakening of the heart.
Common causes:
Atherosclerosis (fatty buildup)
Persistent high blood pressure
Multiple infarctions

41. Pulmonary edema
Occurs when the left side of the heart fails which is called pulmonary congestion.
The right side continues to pump blood to the lungs but the left side is unable to send blood into systemic circulation.
The blood vessels in the lungs become swollen with blood and the pressure increases.
Fluid leaks into the lungs
If untreated, suffocation can occur.

42. Peripheral congestion occurs when the right side of the heart fails
Blood backs up in systemic circulation
Edema occurs in the extremities such as the feet, ankles, and fingers.
The edema causes these regions to become swollen and puffy.