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Internal Features of the Heart - Diagram

Notes

Internal Features of the Heart - Diagram

Sections

Key Features of the Internal 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 - Click for additional images and information.

  • Ensure unidirectional blood flow through the heart.

Right atrioventricular valve

  • Three cusps (aka, leaflets):
    • Anterior
    • Posterior
    • Septal
  • Because it has three cusps, this valve is called the "tricuspid valve."

Left atrioventricular 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).

Semilunar valves:

  • 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).

Right ventricle has three papillary muscles, each named for its location:

  • Anterior
  • Posterior
  • Septal (which is sometimes absent)

Left ventricle typically has two papillary muscles

  • 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
    Irregular ridges of muscle on internal ventricular surface

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).
      Immediately after birth, the interatrial septum fuses, which closes the foramen ovale; the fossa ovalis represents this fusion.
    • 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

Aorta

  • Arises from the left ventricle and arches posteriorly; carries oxygenated blood away from the left ventricle.

Pulmonary trunk

  • 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.

Pulmonary veins

  • Drain into the left atrium; return blood to the heart from the lungs. ("pulmonary" refers to the lungs").

Inferior and Superior vena cavae

  • Return deoxygenated blood from the body to the right atrium

Opening of coronary sinus

  • Returns deoxygenated blood from the myocardium to the heart to right atrium.

Cardiac veins

Full length Text

Here we will learn how the internal features of the heart contribute to its function as a dual-sided muscular pump.

To begin, start a table.
Denote key features of the heart:
Septi (singular = septum) structurally and functionally divide the heart into right and left sides.
Each side operates as a muscular pump:
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.
Valves separate these sides into chambers, and ensure unidirectional blood flow between them:
The atria, superiorly, and, the ventricles, inferiorly.

In our diagram, define right and left sides.
Draw a coronal section of the inferior portion of the heart.
Label the apex; in anatomical position, it points towards the left hip.
Show that the interventricular septum divides this region into left and right ventricles, which contract to pump blood out of the heart.
Notice that the walls of the left ventricle are more muscular and thicker than the walls of the right.
Denote that this difference in wall thickness is functionally significant, because 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.
Then, line the walls of the both ventricles with trabeculae carnae, which are irregular ridges of muscle.

Superior to the ventricles, draw the thin-walled right and left atria; separate them with the interatrial septum.
Indicate that pectinate muscles line the anterior wall of the right atrium. These muscles also exist in the left atrium but are less abundant.
Then, on the interatrial septum, draw the fossa ovalis, which is a shallow depression in the wall of the septum.
Denote that 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).
Immediately after birth, the interatrial septum fuses, which closes the foramen ovale; the fossa ovalis represents this fusion.
In some cases, septal fusion is incomplete (aka, patent foramen ovale), which can impede blood flow and, consequently, blood oxygenation.

Now we'll draw the atrioventricular valves (aka, AV valves), which maintain unidirectional blood flow between the atria and the ventricles.
Indicate that the right atrioventricular valve has three cusps (aka, leaflets), which are continuous with each other at their bases superiorly: Anterior, Posterior, and, Septal.
Because it has three cusps, this valve is called the "tricuspid valve."
Show that the left atrioventricular valve has two cusps: Anterior, and, Posterior.
Because it has two cusps, it is called the bicuspid valve (aka, the mitral valve, because it is mitre-shaped).

These valves attach to papillary muscles, which are special extensions of the trabeculae carneae in the ventricles (papillary refers to their nipple-like shape).
Draw the three papillary muscles of the right ventricle, each named for its location: Anterior, Posterior, and, Septal (which is sometimes absent).
Draw the moderator band (aka, septomarginal trabecula), which spans from the interventricular septum to the base of the anterior papillary muscle. This band prevents the ventricle from overfilling, and contains a portion of the cardiac conduction system (which is addressed in a separate tutorial).
Show that the left ventricle typically has two papillary muscles Anterior and Posterior.

Then, on each side of the heart, show the atrioventricular valves are attached to the corresponding papillary muscles via several short, tough bands called chordae tendineae. The chordae tendineae prevent prolapse (aka, eversion) of the valves, which ensures unidirectional blood flow through the chambers.

Next we'll draw the roots of the great vessels, which are continuous with the chambers of the heart.
First, denote the following definitions:
Arteries send blood away from the heart.
Veins return blood to the heart.

Now, we'll draw the vessels that attach to the left side of the heart:
First, draw the roots of the pulmonary veins draining into the left atrium.
Then, show where the two sets of pulmonary veins open into the left atrium.
Indicate that these vessels return blood to the heart from the lungs. ("pulmonary" refers to the lungs").

Next, show that the aorta arises from the left ventricle and arches posteriorly.
Indicate that the aorta carries oxygenated blood away from the left ventricle.

Now, we'll draw the vessels that attach to the right side of the heart:
Indicate that the pulmonary trunk arises from the right ventricle and splits to form the right and left pulmonary arteries; notice that the right pulmonary artery travels under the arch of the aorta.
Show that the pulmonary arteries carry deoxygenated blood away from the right ventricle, to the lungs
In our table, denote that aortic and pulmonary semilunar valves ensure that blood travels from through the aorta and pulmonary trunk unidirectionally.

Then, in the right atrium, show the openings of the superior and inferior vena cavae.
Superiorly, draw the superior vena cava; indicate that it returns systemic blood from the head, neck, and upper extremities to the right atrium superiorly.
Inferiorly, draw the inferior vena cava; indicate that it returns systemic blood from the torso and lower extremities to the right atrium inferiorly.
Finally, draw the opening for the coronary sinus, which returns deoxygenated blood from the cardiac tissue to the systemic circulation.