Cardiac System Overview

Heart Structure and Function

• The fibrous skeleton of the heart provides structural support, anchors the heart valves, and prevents overstretching.
• The apex of the heart points inferiorly and laterally.
• The human heart typically weighs between 250-350 grams.
• The outermost layer of the heart wall is called the epicardium.
• The pericardium is a sac-like structure surrounding the heart, composed of an outer fibrous layer and an inner serous layer.
• The myocardium is a muscular layer responsible for the heart's pumping action.
• The pericardial cavity is filled with a lubricating fluid, reducing friction during heart contractions.
• The aorta carries oxygenated blood from the left ventricle to the rest of the body.
• Atrioventricular valves prevent backflow of blood from the ventricles to the atria during ventricular contraction.
• The tricuspid valve is located between the right atrium and the right ventricle.
• The mitral valve is located between the left atrium and the left ventricle.
• The pulmonary valve is located between the right ventricle and the pulmonary artery.
• The aortic valve is located between the left ventricle and the aorta.
• The walls of the left ventricle are thicker than those of the right ventricle, reflecting the higher pressure required to pump blood to the systemic circulation
• Pectinate muscles are found in the atria and contribute to atrial contraction.
• The interventricular septum separates the left and right ventricle.
• Heart valves are composed of dense connective tissue.
• Papillary muscles play a crucial role in valve function, preventing prolapse by pulling on the chordae tendineae.
• The left side of the heart is responsible for driving blood to the systemic circulation, delivering oxygenated blood to the body.
• Coronary arteries supply oxygenated blood and nutrients to the heart muscle itself.
• The pulmonary circuit is a low-pressure circulation, responsible for delivering deoxygenated blood to the lungs for gas exchange.
• The right coronary artery branches into the posterior interventricular artery and the marginal artery.
• The left coronary artery branches into the anterior interventricular artery and the circumflex artery.
• Superior and inferior vena cavae drain deoxygenated blood into the right atrium.
• Cardiac muscle cells are striated and interconnected by intercalated discs, allowing for coordinated contraction.
• The coronary sinus collects deoxygenated blood from the heart muscle and empties into the right atrium.
• CO refers to Cardiac Output, a measure of the volume of blood pumped by the heart per minute.
• The first heart sound ('Lub') is caused by the closure of the atrioventricular valves (mitral and tricuspid) at the beginning of ventricular contraction.
• Cardiac Output (CO) is calculated using the formula CO = HR x SV (Heart Rate x Stroke Volume)
• End diastolic volume (EDV) is the amount of blood that collects in a ventricle during diastole (relaxation).
• Preload, contractility, and afterload all influence stroke volume; Heart Rate does not directly affect stroke volume.
• The second heart sound ('Dub') is caused by the closure of the semilunar valves (aortic and pulmonary) at the end of ventricular contraction.
• End Diastolic Volume (EDV) minus End Systolic Volume (ESV) equals Stroke Volume (SV).
• Heart murmurs are abnormal heart sounds, often indicating valve dysfunction or other heart abnormalities.
• Increased venous return increases stroke volume by stretching the heart muscle, leading to a more forceful contraction.
• The Frank-Starling law states that the heart pumps a greater stroke volume when it is filled with more blood (increased EDV), providing a mechanism for matching cardiac output to venous return.
• End systolic volume (ESV) is the amount of blood remaining in the ventricle after contraction.
• Sympathetic nervous system stimulation increases heart rate through the release of norepinephrine.
• Parasympathetic nervous system stimulation decreases heart rate through the release of acetylcholine.
• Hormones like epinephrine and thyroid hormone can increase heart rate.
• Increased body temperature can increase heart rate.

Explore the intricate details of the cardiac system, including the structure of the heart, the pericardium, and the layers of the heart wall. This quiz covers essential concepts such as the cardiovascular system, heart anatomy, and pericarditis. Test your knowledge of how these components function together to support cardiovascular health.