The Cardiovascular System: Heart Structure

Study Notes

Positioned between the lungs, with two-thirds of its mass to the left of the midline.
Apex, the pointed inferior end, formed by the left ventricle, rests on the diaphragm.
Base, the superior portion, is where major blood vessels enter and exit.

Encloses and stabilizes the heart, consisting of an outer fibrous pericardium and an inner serous pericardium.
Fibrous pericardium prevents overstretching, provides protection, and anchors the heart.
Serous pericardium is a double layer: outer parietal pericardium attached to the fibrous layer and inner visceral pericardium (epicardium) adhering to the heart.
The pericardial cavity between the two layers contains pericardial fluid that reduces friction.
Pericarditis refers to inflammation of the pericardium.

Composed of three layers: epicardium (visceral layer of serous pericardium), myocardium (heart muscle), and endocardium (innermost epithelial layer).
Epicardium consists of mesothelium and connective tissue.
Myocardium is thick cardiac muscle responsible for pumping, arranged in interconnected bundles for coordinated contraction.
Cardiac muscle fibers are involuntary, striated, and connected by intercalated discs, allowing the heart to function as a unit.
Endocardium lines the myocardium and is continuous with blood vessel linings.

Contains two upper atria and two lower ventricles, separated by septa.
Interatrial septum features the fossa ovalis, an oval depression.
Auricles, pouch-like structures, are present at the surface of each atrium.
Interventricular septum separates the right and left ventricles.
Atria have thinner myocardium; ventricles are thicker due to pumping functions—right ventricle to lungs, left ventricle to the body.

Deoxygenated blood enters the right atrium via the superior vena cava (upper body), inferior vena cava (lower body), and coronary sinus (heart's blood vessels).
Blood flows from the right atrium to the right ventricle, then into the pulmonary trunk, splitting into right and left pulmonary arteries for lung oxygenation.
Oxygenated blood returns through four pulmonary veins into the left atrium, moves to the left ventricle, and enters the ascending aorta to supply the body.

Four valves: two atrioventricular (AV) and two semilunar valves, composed of connective tissue and endothelium.
Valves prevent backflow of blood, ensuring proper circulation.
Atrioventricular valves: tricuspid (right atrium to right ventricle) and bicuspid (mitral) valve (left atrium to left ventricle).
Chordae tendineae tethered to papillary muscles prevent valve reversal during ventricular contraction.
Semilunar valves prevent backflow into the ventricles from arteries.