Corpus: Right ventricle

The ventriculus cordis dexter is the right-sided heart chamber of domestic mammals. It corresponds to the right ventricle in humans.

The right ventricle receives its blood from the right atrium via the ostium atrioventriculare dextrum. During cardiac activity (systole), the right ventricle transports the deoxygenated blood via the conus arteriosus and the adjoining pulmonary trunk into the lungs under relatively low pressure.

Morphology[Bearbeiten]

The wall of the ventriculus cordis dexter is less than half as thick as the wall of the left ventricle due to its lower working capacity. It extends from the sulcus interventricularis subsinuosus - forming the margo ventricularis dexter - to the sulcus interventricularis paraconalis.

Due to the convex inner wall formed by the interventricular septum, the lumen of the right ventricle appears crescent-shaped in cross-section. This shape is particularly visible during cardiac contraction.

Inflow and outflow tract[Bearbeiten]

Within the internal space of the right ventricle, two functional sections can be distinguished. The actual ventricular cavity extends from the ostium atrioventriculare dextrum towards the apex of the heart and is known as the inflow tract. The second delimitable cavity comprises the funnel-shaped conus arteriosus from the apex of the heart, which continues into the pulmonary trunk. This section is also known as the outflow tract.

In the inflow area, the ventricular wall - especially in the sections close to the interventricular sulci - is equipped with so-called trabeculae carneae. Such trabeculae carneae are absent in the wall sections adjacent to the outflow tract, particularly in the area of the conus arteriosus.

In addition to the trabeculae carneae, there are also a variable number of roundish muscle cords that create a cross-connection between the interventricular septum and the outer wall of the ventricle. One of these cords is particularly strong and runs from the ventricular septum below the subarterial papillary muscle to the base of the papillary muscle. It is known as the septomarginal trabecula and is part of the heart's conduction system. In addition to this constantly developed muscle beam, there are usually other cross-connections within the right ventricle. These can be made up of either working muscles or connective tissue. In some cases, they also contain special cell groups that play an important role in the conduction system as Purkinje fibres.

Papillary muscles[Bearbeiten]

Three so-called papillary muscles (musculi papillares) protrude into the right ventricle. These functionally important muscle bundles differ from species to species both in their shape and in their individual number. The three mastoid muscles are named according to their location:

• Musculus papillaris subarteriosus: septal or near the pulmonary trunk
• Musculi papillares parvi: combination of several small individual muscles that form a functional unit
• Musculus papillaris magnus: is the most strongly developed and located on the outer wall or, in carnivores, can also extend to the septum or be located there

Groups of tendon threads, the chorda tendineae, originate from the papillary muscles. These tendinous filaments fan out and then radiate into the free edges and the surfaces of the three-part leaflet valve (valva atrioventricularis dextra) facing the ventricle.

Valva atrioventricularis dextra[Bearbeiten]

The right atrioventricular valve originates from a tendinous ring (annulus fibrosus) that surrounds the ostium atrioventriculare dextrum. Shortly after the origin, the valve divides into three cusps that protrude into the ventricular lumen and can form additional cusps. Each of these three main cusps is attached to two mastoid muscles by the tendinous sutures. The valve cusps are labelled according to their position.

• Cuspis septalis valvae atrioventricularis dextrae: septal cusp
• Cuspis parietalis valvae atrioventricularis dextrae: outer wall tip
• Cuspis angularis valvae atrioventricularis dextrae: small cranial tip located at an angle between the cusps mentioned above

The valva atrioventricularis dextra acts as a non-return valve. The papillary muscles with their chordae tendineae ensure that the tension of the valves is maintained during the various phases of the heart's action, which are accompanied by a shift in the valve plane. During the filling phase of the heart (diastole), blood can flow through the open leaflet valve from the right atrium into the right ventricle. With the onset of systole and the simultaneous onset of the pressure increase phase, the valva atrioventricularis dextra is closed. This closing mechanism occurs when its tips unfold due to the tension exerted by the papillary muscles on the chordae tendineae and lie against each other over a wide area. This means that the blood in the right ventricle can only escape via the expulsion pathway (conus arteriosus).

Valva trunci pulmonalis[Bearbeiten]

To prevent the blood from flowing back into the ventricle during diastole, a closure mechanism must also be formed at the junction between the pulmonary trunk and the right ventricle. A linear blood flow is ensured by the three-part pulmonary valve, valva trunci pulmonalis, contained in the ostium of the pulmonary trunk. This pocket valve is formed by three crescent-shaped valvulae semilunares. The pockets are labelled according to their position in space:

• Valvula semilunaris sinistra
• Valvula semilunaris dextra
• Valvula semilunaris intermedia

The pocket flap consists of an endothelial duplication, which is reinforced by a medium-sized sheet of collagen fibres. It attaches to the fibrous ring (annulus fibrosus) of the ostium trunci pulmonalis and protrudes into the lumen of the vessel in a crescent or half-shell shape with a peripherally directed depression. Its free edge has slight reinforcements so that a small, coarse nodule (nodulus valvulae semilunaris) is formed in the centre. This nodule is flanked on both sides by a crescent-shaped, transparent flap section, which in turn is known as the lunula valvulae semilunaris. In the area of the three valvulae semilunares, the vessel wall is widened to form the sinus trunci pulmonales.

Similar to the atrioventricular valve, the semilunar valve also acts as a non-return valve in the ostium trunci pulmonalis. During the expulsion phase, the upstream blood pressure places the pockets against the vessel wall so that the valve is open. As soon as the pressure in the vessel drops and diastole occurs, the pockets are filled with blood by the downstream pressure of the blood column, forcing the valve to close. The marginal valvular nodules ensure that the valve closes completely in the centre.

• Nickel, Richard, August Schummer, Eugen Seiferle. Volume III: Circulatory system. Textbook of the anatomy of domestic animals. Parey, 2004.
• Salomon, Franz-Viktor, Geyer, Hans, Uwe Gille. Anatomy for veterinary medicine. Enke-Verlag, 2005.