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Questions and Answers
Where is the heart located?
Where is the heart located?
Left side of the mediastinum
Which layer of the heart is the outermost?
Which layer of the heart is the outermost?
- Endocardium
- Epicardium (correct)
- Myocardium
- Pericardium
What does the pericardial sac do?
What does the pericardial sac do?
- Produces red blood cells
- Regulates blood pressure
- Stores electrical impulses
- Encases and protects the heart from trauma (correct)
The myocardium is the innermost layer of the heart.
The myocardium is the innermost layer of the heart.
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How many heart chambers are there?
How many heart chambers are there?
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What happens to the atrioventricular valves during ventricular contraction?
What happens to the atrioventricular valves during ventricular contraction?
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What is the function of the SA node?
What is the function of the SA node?
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The AV node can only sustain a heart rate of 60 to 100 beats per minute.
The AV node can only sustain a heart rate of 60 to 100 beats per minute.
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Which artery supplies blood to the anterior wall of the left ventricle?
Which artery supplies blood to the anterior wall of the left ventricle?
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The heart has ______ valves.
The heart has ______ valves.
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What type of blood does the right atrium receive?
What type of blood does the right atrium receive?
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Study Notes
Anatomy and Physiology of the Heart
- The heart is situated on the left side of the mediastinum.
- Comprised of three layers:
- Epicardium: the outermost layer.
- Myocardium: the middle layer, the heart's contracting muscle.
- Endocardium: the innermost layer, lining the heart's chambers and valves.
Pericardial Sac
- Encases and protects the heart from trauma and infection.
- Two layers:
- Parietal pericardium: tough, fibrous outer membrane, attaching to the sternum, thoracic vertebrae, and diaphragm.
- Visceral pericardium: thin inner layer closely adhering to the heart.
- Pericardial space contains 5 to 20 mL of fluid for lubrication and cushioning.
Heart Chambers
- Four chambers in total:
- Right atrium: receives deoxygenated blood via superior and inferior vena cava.
- Right ventricle: pumps blood to the lungs through the pulmonary artery.
- Left atrium: receives oxygenated blood from the lungs via four pulmonary veins.
- Left ventricle: largest chamber, pumps oxygenated blood into systemic circulation via the aorta.
Heart Valves
- Four valves:
- Atrioventricular valves:
- Tricuspid valve: located on the right.
- Mitral (bicuspid) valve: located on the left.
- Close during ventricular contraction to prevent backflow and open during relaxation.
- Semilunar valves:
- Pulmonic valve: between right ventricle and pulmonary artery.
- Aortic valve: between left ventricle and aorta.
- Prevent backflow into ventricles, opening during contraction and closing during relaxation.
- Atrioventricular valves:
Conduction System of the Heart
- Sinoatrial (SA) node: main pacemaker; located at the junction of the superior vena cava and right atrium; generates impulses at 60-100 beats per minute.
- Atrioventricular (AV) node: located in the lower atrial septum; receives impulses from the SA node; can initiate heart rate of 40-60 beats per minute if necessary.
Bundle of His and Purkinje Fibers
- Bundle of His: continuation of the AV node; located at the interventricular septum; branches into right and left bundle branches.
- Purkinje fibers: network beneath the ventricular endocardium; can serve as pacemaker with rates of 20-40 beats per minute when higher pacemakers fail.
Coronary Arteries
- Right main coronary artery: supplies the right atrium and ventricle, inferior left ventricle, posterior septal wall, and SA/AV nodes.
- Left main coronary artery: has two branches:
- Left anterior descending (LAD) artery: supplies anterior left ventricle and anterior septum.
- Circumflex artery: supplies left atrium and lateral/posterior surfaces of the left ventricle.
Heart Sounds
- First heart sound (S1): indicative of valve function and cardiac activity.
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