Heart - Internal Features
Notes
Key Features of the Internal Heart:
- The right side of the heart receives deoxygenated blood from the body and sends it to the lungs.
- The left side of the heart receives oxygenated blood from the lungs and sends it to the body.
- Review Systemic vs. Pulmonary Circulation
- Review of Blood flow through the heart
Septi (singular = septum)
- Structurally and functionally divide the heart into right and left sides; each side operates as a muscular pump.
- Interventricular septum divides right and left ventricles, inferiorly.
- Interatrial septum divides right and left atria, superiorly.
Chambers
- Atria
- Superior chambers
- Ventricles
- Inferior chambers
Valves
- Ensure unidirectional blood flow through the heart.
- Three cusps (aka, leaflets):
- Anterior
- Posterior
- Septal
- Because it has three cusps, this valve is called the "tricuspid valve."
- Two cusps:
- Anterior
- Posterior
- Because it has two cusps, it is called the bicuspid valve (aka, the mitral valve, because it is mitre-shaped).
- Aortic and pulmonary semilunar valves ensure that blood travels from through the aorta and pulmonary trunk unidirectionally.
Papillary muscles
- Anchor AV valves.
- Special extensions of the trabeculae carneae in the ventricles (papillary refers to their nipple-like shape).
- The moderator band (aka, septomarginal trabecula) spans from the interventricular septum to the base of the anterior papillary muscle; it prevents the ventricle from overfilling, and contains a portion of the cardiac conduction system (which is addressed in a separate tutorial).
- Anterior
- Posterior
- Septal (which is sometimes absent)
- Anterior
- Posterior
Chordae tendineae
- Short cords that attach flaps of valves to papillary muscles to prevent prolapse (aka, eversion) of the valves, and ensure unidirectional blood flow through the chambers.
Features of the Ventricles:
- Walls of the left ventricle are more muscular and thicker than the walls of the right.
- The left ventricle must produce more muscular force to pump blood to the body; in contrast, the right ventricle produces less force, as it sends blood to the nearby lungs.
- Trabeculae carnae
Features of the Atria:
- Pectinate muscles line the anterior wall of the right atrium. These muscles also exist in the left atrium but are less abundant.
- Fossa ovalis is a shallow depression in the wall of the interatrial septum.
- The fossa ovalis is clinically significant from the moment of birth, when it seals off an opening in the interatrial septum called the foramen ovale.
- In utero, the foramen ovale shunts blood directly from the right to left atrium, which allows the blood to bypass the nonfunctional lungs (the fetus receives oxygen directly from the maternal blood via the placenta).
- In some cases, septal fusion is incomplete (aka, patent foramen ovale), which can impede blood flow and, consequently, blood oxygenation.
Great vessels
- Arteries send blood away from the heart
- Veins return blood to the heart
- Arises from the left ventricle and arches posteriorly; carries oxygenated blood away from the left ventricle.
- Arises from the right ventricle and splits to form the right and left pulmonary arteries; pulmonary arteries carry deoxygenated blood away from the right ventricle, to the lungs.
- Drain into the left atrium; return blood to the heart from the lungs. ("pulmonary" refers to the lungs").
- Return deoxygenated blood from the body to the right atrium
- Returns deoxygenated blood from the myocardium to the heart to right atrium.
Click to view Ventricular and Outflow Development