1. Chapter 20
The Heart 1 1

2. Position, Size, and Shape
Heart lies in mediastinum (a central compartment of the thoracic cavity made of loose connective tissue) between lungs; 2/3 of its mass is to the left of the midline
Size: equivalent to a person’s closed fist.
Shape: cone-shaped, pointed apex inferior; flat base is superior.
Heart protected on the anterior side by the sternum; on the posterior side by the vertebrae
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Aorta
Pulmonary
trunk
Base of
heart
Apex
of heart
Diaphragm
(c)

3. SULCI - GROOVES on surface of heart containing blood vessels and fat
coronary sulcus
Separates the atria from the ventricles
anterior interventricular sulcus
marks the boundary between ventricles anteriorly
posterior interventricular sulcus
marks the boundary between ventricles posteriorly

4. Protective layers of the heart
Pericardium – 2 layered sac surrounds and protects the heart from external jerk or shock.
Fibrous pericardium dense irregular connective tissue, protects and anchors the heart to diaphragm and mediastinum; prevents overstretching
Serous pericardium
Parietal pericardium
Visceral pericardium (epicardium) covers the heart surface and becomes part of the heart wall
Pericardial cavity lies between the parietal and visceral layers of the serous pericardium; filled with pericardial fluid that reduces friction between the two membranes.
pericarditis. inflammation of the pericardium
cardiac tamponade buildup of fluid in the pericardial cavity
pericarditis: inflammation of the pericardium
cardiac tamponade: buildup of fluid in the pericardial cavity- resulting in slow or rapid compression of the heart.

5. Heart Wall Epicardium (visceral pericardium)
visceral serous membrane covering heart; adipose in thick layer in some places
Contain coronary blood vessels
Myocardium
cardiac muscle layer
Endocardium
covers the valve surfaces and continuous with endothelium of blood vessels

6. 4 CHAMBERS
2 upper atria
2 lower ventricles

7. Right and Left Atrium
Pectinate muscles internal ridges of myocardium in right atrium and right auricle. Increase force of contraction w/o increasing heart mass
Interatrial septum separates right and left atrium
Auricle flap like extension increases surface area.
RIGHT ATRIUM
Receives blood from 3 veins: superior / inferior vena cava, coronary sinus
Blood flows through the right atrioventricular valve (AV valve) or the tricuspid valve) into the right ventricle.
Each valve consists of 2-3 fibrous flaps of tissue called cusps.
LEFT ATRIUM
Forms MOST of the base (top) of the heart
Receives blood FROM LUNGS via 4 pulmonary veins (2 right / 2 left) Remember blood always returns to the heart via veins
Blood flows through the left atrioventricular valve (AV valve) or the bicuspid valve (has 2 cusps) into the left ventricle.
This valve is also known as the mitral valve.

8. http://europace. oxfordjournals. org/content/9/suppl_6/vi3/F3. large
Pectinate muscles
internal ridges of myocardium in right atrium and both left and right auricles. Increase force of contraction w/o increasing heart mass
NOTE: difference in myocardium thickness between left and right ventricles

9. Right and Left Ventricle
Inside ventricles are raised bundles of cardiac muscle called trabeculae carneae
cone shaped traberculae carnae are called papillary muscles.
Chordae tendineae cords connect cusps of the AV valves to the papillary muscles
Interventricular septum: partitions the right and left ventricles
RIGHT VENTRICLE
Blood flows from the right ventricle into the pulmonary trunk (pulmonary artery) through the pulmonary semilunar valve.
LEFT VENTRICLE
The aortic semilunar valve allows the passage of blood from ventricle to the ascending aorta
just above valve are openings to the coronary arteries
Myocardium much thicker in the left ventricle - produces greater force for blood ejection to systemic tissues

12. Fibrous cardiac skeleton collagenous and elastic fiber provides
Heart Valves
Fibrous cardiac skeleton collagenous and elastic fiber provides
support structure
attachment for cardiac muscle
anchor for valve tissue
electrically insulate ventricular cells from atrial cells
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Left AV
(bicuspid) valve
Right AV
(tricuspid) valve
Fibrous
skeleton
Openings to
coronary arteries
Aortic
valve
Pulmonary
valve
(a) 12

13. Valve Disorders
Stenosis - narrowing of a heart valve which restricts blood flow.
Rheumatic Fever- inflammatory disease that occurs following a Streptococcus pyogenes infection (usually in the throat).
The immune system stimulates antibodies to attack the infection. Inadvertently, the antibodies also attack the heart tissue damaging the heart valves. The damaged valves can lead to heart failure.
Mitral valve prolapse- bulge too far into the left atrium during contraction

14. Heart Sounds
The sound of a heartbeat comes primarily from the turbulence in blood flow caused by the closure of the valves.
Listening to sounds within the body is called auscultation, usually done with a stethoscope.
First heart sound S1 (lubb) created by blood turbulence associated with the closing of the atrioventricular valves
The second heart sound S2 (dupp) represents the closing of the semilunar valves close to the end of the ventricular systole.

15. Murmurs
A heart murmur is an abnormal sound that consists of a flow noise that is heard before, between, or after the lubb-dupp or that may mask the normal sounds entirely.
Not all murmurs are abnormal or symptomatic, but most indicate a valve disorder.
Sounds are thought to be produced by regurgitation through valves

16. Specialized Anatomy of Fetal Heart Circulation
Foramen ovale
an opening through interatrial septum in the right atrium
Connects the two atria
Seals off at birth, forming fossa ovalis

17. Clinical Problems
Coronary Artery Disease (CAD) - partial or complete blockage of coronary circulation
Atherosclerosis condition in which an artery wall thickens as a result of the accumulation of fatty materials (plaque) results in artery spasm or clot
Arteriosclerosis hardening/loss of elasticity of medium or large arteries
Arteriolosclerosis hardening/loss of elasticity of arterioles
Myocardial infarction (MI) (heart attack)
Angina pectoris – temporary ischemia (slow blood flow)- obstructing 75% or more of the blood flow to cardiac muscle-

19. Clinical Problems
Congenital Heart Defect an abnormality or defect that exists AT or BEFORE birth.
Arrhythmia (dysrhythmia) is an irregularity in heart rhythm resulting from a defect in the conduction system of the heart.
Bradycardia- slow rate below 60 bpm
resting-sleep, well-conditioned hearts
Tachycardia – fast rate above 100 bpm
stress, anxiety, drugs, heart disease
Fibrillation – asynchronous contraction that can kill very easily- heart loses its rhythm- some parts of the atria and ventricle contract while others remain un-stimulated

20. Cardiac Conduction System
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SA node fires. 2
Excitation spreads through
atrial myocardium.
Right atrium 1 2
Sinoatrial node
(pacemaker)
Left
atrium 3
AV node fires. 2
Purkinje
fibers
Atrioventricular
node 3 4
Excitation spreads down AV
bundle.
Bundle
branches
Atrioventricular
bundle 5
Purkinje fibers distribute
excitation through
ventricular myocardium. 4 5
Purkinje fibers

21. Electrocardiogram---ECG or EKG
A recording of the electrical changes (“ACTION POTENTIAL”) that accompany each cardiac cycle (heartbeat)
Equipment detects and amplifies electrical changes on the skin when the heart muscle impulse is generated
ECG helps to determine abnormal conduction pathway; if the heart is enlarged or has damaged regions

22. Electrocardiogram---ECG or EKG
P wave
atrial depolarization
systole
P to Q interval
conduction time from SA node to AV node
QRS complex
Atrial repolarization
diastole
Ventricular depolarization ST
plateau period of sustained contraction
T wave
ventricular repolarization
ECG/EKG Good Animation
(3.34 min)

23. Normal Electrocardiogram (ECG)

24. Atria contract
Ventricles contract

26. atrial depolarization begins
2) atrial depolarization complete (atria contracted)
ventricles begin to depolarize at apex; atria repolarize (atria relaxed)
ventricular depolarization complete (ventricles contracted)
ventricles begin to repolarize at apex
6) ventricular repolarization complete (ventricles relaxed)