Overview
This lecture covers the anatomy of the heart, focusing on its layers, chambers, valves, and the basic flow of blood through the heart.
Layers of the Heart
- The heart has three main layers: endocardium (inner), myocardium (middle, muscular), and pericardium (outer sac).
- The endocardium lines the heart chambers and is continuous with the heart valves.
- The myocardium consists of cardiac muscle responsible for heart contractions.
- The pericardium surrounds the heart, with a visceral layer (closest to heart) and a parietal layer (outer).
- The pericardium produces serous fluid to lubricate the heart and reduce friction during contractions.
Heart Chambers and Orientation
- The heart has four chambers: two atria (upper) and two ventricles (lower).
- Always describe “left” and “right” from the patient's perspective.
- Blood always enters the atria and moves from atria to ventricles.
Heart Valves and Their Function
- Valves ensure one-way blood flow between chambers.
- The right atrioventricular valve is the tricuspid valve (three cusps).
- The left atrioventricular valve is the bicuspid (mitral) valve (two cusps).
- Valves prevent blood from flowing backward in the heart.
Blood Flow Through the Heart
- Right side receives low-oxygen blood from the body via the superior and inferior vena cava.
- Blood flows from right atrium → tricuspid valve → right ventricle → pulmonary semilunar valve → pulmonary trunk → right and left pulmonary arteries → lungs.
- Oxygenated blood returns from lungs via pulmonary veins to left atrium.
- Blood flows from left atrium → bicuspid (mitral) valve → left ventricle → aortic semilunar valve → aorta → body.
- Arteries always carry blood away from the heart; veins return blood to the heart.
Key Terms & Definitions
- Endocardium — inner lining of the heart chambers, continuous with the valves.
- Myocardium — thick, muscular, middle layer of the heart responsible for contractions.
- Pericardium — outer sac surrounding the heart, containing serous fluid for lubrication.
- Atrium (Atria) — upper heart chambers that receive incoming blood.
- Ventricle — lower heart chambers that pump blood out of the heart.
- Valve — structure that ensures one-way blood flow between heart chambers.
- Tricuspid Valve — right atrioventricular valve with three cusps.
- Bicuspid (Mitral) Valve — left atrioventricular valve with two cusps.
- Semilunar Valve — valve at the base of large arteries leaving ventricles (pulmonary/aortic).
- Aorta — main artery carrying oxygenated blood from the left ventricle to the body.
- Vena Cava — large veins returning deoxygenated blood from the body to the heart.
- Pulmonary Artery/Vein — vessel carrying blood to/from the lungs.
Action Items / Next Steps
- Review diagrams labeling heart chambers, valves, and major vessels.
- Memorize the sequence of blood flow through the heart.
- Learn the function and locations of each heart valve.