Anatomy of the Heart Lecture Notes

Overview

• The heart is located in the thoracic cavity within the mediastinum.
• It is shifted approximately two-thirds to the left of the mid sternal line.
• The apex points towards the left hip, while the base points towards the right shoulder.
• The heart weighs about 200 to 300 grams, roughly the size of a fist.

Chambers of the Heart

Atria

• The heart has four chambers: right atrium, left atrium, right ventricle, and left ventricle.

• The two top chambers are the atria (plural of atrium).

• Right Atrium:

  • Receives blood from:
    • Inferior Vena Cava (IVC): blood from below the diaphragm.
    • Superior Vena Cava (SVC): blood from above the diaphragm.
    • Coronary Sinus: drains blood from heart tissue.
  • Contains fossa ovalis, a remnant of the fetal foramen ovale.

• Left Atrium:

  • Receives blood from the lungs via the pulmonary veins:
    • Left Pulmonary Vein: from the left lung.
    • Right Pulmonary Vein: from the right lung.

Valves

• Atrioventricular Valves:

  • Tricuspid Valve: separates right atrium from right ventricle.
  • Bicuspid (Mitral) Valve: separates left atrium from left ventricle.

• Semilunar Valves:

  • Pulmonary Semilunar Valve: separates right ventricle from pulmonary trunk.
  • Aortic Semilunar Valve: separates left ventricle from aorta.

Heart Structure and Function

Chordae Tendineae and Papillary Muscles

• Chordae Tendineae: collagen cords anchoring valve flaps to prevent backflow.
• Papillary Muscles: muscles that anchor chordae tendineae, ensuring valve closure.

Interventricular Septum

• The interventricular septum separates the left and right ventricles.
• Important for preventing blood mixing between the two sides.
• Interatrial Septum: separates left and right atria.

Great Vessels

• Pulmonary Trunk: splits into left and right pulmonary arteries.
• Aorta: divided into ascending aorta, aortic arch, and branches:
  • Brachiocephalic artery
  • Left Common Carotid Artery
  • Left Subclavian Artery

Layers of the Heart

1. Endocardium: innermost layer lining the heart chambers.
2. Myocardium: middle layer composed of cardiac muscle tissue, thicker on the left side.
3. Epicardium (Visceral Layer of Serous Pericardium): outermost layer of the heart.
4. Pericardial Cavity: contains serous fluid to reduce friction during heart contractions.
5. Parietal Layer of Serous Pericardium: lines the fibrous pericardium.
6. Fibrous Pericardium: dense connective tissue providing:
   • Anchoring of the heart.
   • Protection against trauma.
   • Prevention of overfilling with blood.

Clinical Relevance

• Pericarditis: inflammation causing pain due to friction between layers.
• Importance of the myocardium in heart pumping efficiency and its thickness in left vs. right ventricles.

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Conclusion

• Thorough understanding of heart anatomy, chambers, valves, great vessels, and the layers is crucial for studying the cardiovascular system.