Summary of "Thorax 3 - Anatomie du cœur [Heart external morphology and cardiac cavities]"

Summary of "Thorax 3 - Anatomie du cœur [heart external morphology and cardiac cavities]"

This detailed lecture covers the external and internal morphology of the human heart, emphasizing its anatomical features, clinical significance, and functional aspects. The content is structured around the heart’s position, external shape, surfaces, borders, and detailed anatomy of the four cardiac chambers and valves. It also introduces the clinical relevance of cardiac auscultation and imaging.

Main Ideas and Concepts

1. General Introduction to the Heart

The heart is a hollow muscular organ located in the middle mediastinum of the thorax.
It functions as a pump to circulate blood, a fact established by William Harvey in the 17th century.
On chest X-ray, the heart appears as the "cardiac shadow," a radiological silhouette framed by thoracic structures.
The heart rests on the diaphragm’s tendinous center (phrenic center), contributing to its central shadow on imaging.

2. External Morphology of the Heart

The heart is roughly shaped like a triangular pyramid, with:
- A posterior base (atria)
- An apex (tip of the left ventricle)
- Three main surfaces (faces):
  - Anterior (sternocostal) face: in contact with the sternum and ribs; includes parts of the right atrium, right ventricle, and left ventricle.
  - Pulmonary (left) face: faces the left lung, formed mainly by the left ventricle.
  - Diaphragmatic (inferior/posterior) face: rests on the diaphragm, formed by the left and right ventricles.
Borders of the heart correspond to edges of these faces and relate to major vessels and chambers.
The sternocostal face includes:
- Right atrium and its extension (right auricle)
- Right ventricle (largest part of anterior surface)
- Left ventricle (left portion and apex)
The posterior face shows the left atrium and pulmonary veins, right atrium with venae cavae, pulmonary trunk, and ascending aorta.
The apex is formed by the tip of the left ventricle and is palpable at the 5th-6th left intercostal space near the nipple.

3. Clinical Examination and Imaging

The heart is examined by:
- Auscultation (listening to valve sounds with a stethoscope)
- Palpation (feeling heartbeats on the chest wall)
- Imaging: ultrasound (transthoracic or transesophageal), CT scan, MRI.
Cardiac morphology knowledge is essential for interpreting clinical findings and imaging.

4. Internal Morphology: Cardiac Cavities and Valves

The heart contains four cavities:
- Right atrium and right ventricle
- Left atrium and left ventricle
Right and left sides are separated by the cardiac septum (interatrial and interventricular septa).

Right Heart:

Right atrium: receives venous blood from superior and inferior vena cava; roughly ovoid.
- Contains the right auricle (right atrial appendage).
- Opens into the right ventricle through the tricuspid valve (right atrioventricular valve).
Right ventricle: triangular pyramid shape with anterior, posterior (diaphragmatic), and septal faces.
- Contains papillary muscles and chordae tendineae that anchor the tricuspid valve.
- Pumps blood into the pulmonary trunk via the pulmonary valve (semilunar valve).
Valves on the right side ensure unidirectional blood flow and prevent reflux.
The pulmonary valve has three semilunar cusps and no chordae tendineae.

Left Heart:

Left atrium: flattened, receives oxygenated blood from four pulmonary veins.
- Opens into the left ventricle through the mitral valve (left atrioventricular valve).
Left ventricle: conical shape, thick muscular wall due to high pressure needed to pump blood into systemic circulation.
- Contains two large papillary muscles with chordae tendineae anchoring the mitral valve.
- Pumps blood into the ascending aorta through the aortic valve (three semilunar cusps).
The aortic valve prevents reflux of blood from the aorta back into the left ventricle.
Coronary arteries originate just above the aortic valve cusps.