For comparison, see heart dissections of a ferret, a fox, and a tree shrew.

THORACIC CAVITY- HEART AND VESSELS DISSECTION

Using dissection scissors, we cut the rib cage on each side as laterally as possible. We cut through the ribs sagittally and the manubrium transversely. We took care to keep these cuts superficial so that the deep organs and vessels of the thorax remained intact and undamaged. The rib cage was then reflected inferiorly to expose the lungs and mediastinum.

To remove the lungs, the pulmonary arteries and veins, and bronchii were cut and the lungs were gently removed from the trachea attachment, and from the thorax with tweezers.

Points of Note:

The right lung is much larger than the left lung. The right lung fills the whole right side of the thorax, whereas the left lung shares the left side of the thorax with the heart, which is in the slightly off-center mediastinum. The lungs are covered with a thin clear film of the parietal and visceral pleura, and the heart is covered with the film of the parietal and visceral pericardium.

The right lung has three lobes (upper, middle, and lower) and the left lung has only two lobes (upper and lower). The upper lobes of both lungs are the largest, in the right lung comprising about 60% of the whole lung mass, and in the left lung comprising about 80%. The lower lobes are the smallest, comprising about 20% of each lung. The lobes of the lungs are separated by deep grooves, or fissures.

Removing the lungs exposes the area deep to the left lung, allowing the aorta and branches to be observed. The aorta is a small tube dorsal to the esophagus, which runs dorsally to the trachea. Several anatomical relationships aid in the identification of the many small, tubular structures in the thorax:
1. The trachea is most readily identified at the exposed ventral neck, as it is the most medial, superficial tube, and has transverse cartilaginous rings. The trachea can then be followed as it splits into the bronchii, which enter the lungs.
2. The esophagus is the slender tube that runs medially down the thorax, deep to the trachea, and goes through the diaphragm to the abdomen.
3. The aorta originates from the deep side of the left ventricle of the heart, running cranially (ascending aorta) and then forming an arch and moving caudally (descending aorta) to perforate the diaphragm to enter the abdomen, giving off arterial branches along the way.

The diaphragm (innervated by the phrenic nerves) is a gray transverse lining separating the thorax from the abdomen.

The heart is divided into four sections: the right and left atria (more cranial portions of the heart) and the right and left ventricles (more caudal). The right atrium is where the deoxygenated blood enters the heart, moves to the right ventricle where it is pumped to the lungs for oxygenation, returning to the heart through the left atrium to the left ventricle, where it is pumped to the rest of the body. The ventricles are more muscular than the atria, as they perform the "pumping action". In the natural orientation of the bat, the dark brown ventricles dominate the ventral side, with the small, paler right atrium exposed as a small sliver on the cranial ventral side. The left ventricle is so large that the left atrium is not visible from the ventral side, as it has been pushed dorsally.

Note that this species, Tadarida braziliensis, has two anterior venae cavae and one posterior vena cava.

Reference:

Tabular information from:
Kallen, F.C. 1970. "Cardiovascular system of bats", p. 289-483 in Wimsatt, W.A. (ed.) Biology of Bats: Vol. 4. Academic Press, New York.

Links:

to Comparative Mammalian Anatomy home

to mammalian hearts