Lungs and heart
In this specimen we can see the heart surrounded by lungs on both sides. The trachea can also be seen. The surfaces of lungs such as the inferior and sternocostal surfaces are visualized here. The borders such as the right border which separates the sternocostal surface from the mediastinal surface and the inferior border separating the sternocostal surface from the inferior surface are also seen.
On the left side we can also see the cardiac notch where the heart is in direct contact with the chest wall. This is the place where we have the area of superficial cardiac dullness. Tongue shaped projection called lingula is also seen in the left lung.
The heart is a conical hollow muscular organ situated in the middle mediastinum. It is four chambered and is enclosed by the pericardium. The heart pumps blood to various parts of the body to meet the nutritional requirements.
The lungs are the paired respiratory organs situated in the pleural cavity. They aid in the oxygenation of the blood. Each lung is conical in shape with a rounded apex, a broad base or diaphragmatic surface, costal surface and medial surface separated by three borders. The right lung is divided into three lobes (upper, middle and lower) by two fissures (oblique and horizontal). The left lung is divided into two lobes (upper and lower) by an oblique fissure.
The trachea (Latin, air vessel; also called the wind-pipe) is a 10-15 cm long tube situated in the lower part of the neck and superior mediastinum. Its upper under is continuous with the larynx at the level of C6 vertebra. It is made up of C-shaped cartilaginous rings (hyaline in nature and 16-20 in number) anteriorly. Posteriorly the gap is closed by a fibro-elastic membrane and contains trachealis muscle. At the level of the sternal angle (i,e, lower border of T4 vertebra) the trachea bifurcates into two principal bronchi.
Inferior surface of heart:
The inferior surface of the heart rest on the central tendon of the diaphragm (also called the diaphragmatic surface). It is formed by both right and left ventricles of the heart.
Sternocostal surface of heart:
The sternocostal surface of the heart is formed by the right atrium, right auricle, right ventricle, small strip of left ventricle and left auricle.
Right border of heart:
The right border of the heart is formed entirely by the right atrium and extends from the opening of the superior vena cava to the inferior vena cava.
Inferior border of heart:
The inferior border of the heart is mainly by the right ventricle and partly by the left ventricle.
The cardiac notch is a lateral deviation of the anterior border of the left lung. It is produced to accommodate the heart.
Area of superficial cardiac dullness:
Percussion of the anterior chest wall reveals an area of dullness over the center and left of the sternum. It corresponds to the cardiac notch wherein the heart and pericardium is not covered by the lung and pleura. This is the area of superficial cardiac dullness.
The lingula is a tongue shaped projection extending from the lower part of the upper lobe of the left lung, inferior to the cardiac notch. It represents the middle lobe of the left lung.