VAN 121: Veterinary Gross Anatomy-II (2+2)

RIGHT VENTRICLE

• The right ventricle forms the anterior part of the ventricular mass and forms the anterior border of the heart. It does not reach the apex of the heart.
• It is triangular in outline and crescentric on cross section.
• It communicates above at the base with the right atrium through the right atrio- ventricular orifice but its left part projects higher forming the conus arteriosus from which the pulmonary artery arises.
• The apex of the right ventricle is two inches above the apex of the heart.
• The septal wall is convex and faces obliquely forward and to the right.

The following features are seen in the interior

• The endocardium.
• The rounded musculo-tendinous cord called as moderator band extending from the interventricular septum to the right lateral wall.
• The number, size and position are usually variable. Generally one large band is noticed. It is supposed to prevent over distension of the right ventricle.
• The wall of the ventricle except in the conus arteriosus bear muscular ridges called trabeculae carneae.
•  A variety of these in the form of conical, flattened projections are the musculi papillaris and are three in number in the right ventricle.
• These are continuous at their bases with the walls of the ventricle and at the apices they give attachment to the chordae tendinae which are fibrous cords attached at their other ends to the cusps of the atrio-ventricular valve.
• The right atrio-ventricular orifice is large oval opening guarded by the tricuspid valve made up of three cusps. Of these, one is between the ventricular orifice and the conus arteriosus; other is against the ventricular septum and another on the right margin.
• The peripheral edges of the cusps are attached to the fibrous ring of the atrio-ventricular opening and the central edges hang down into the ventricle and give attachment to the chordae tendinae. The auricular surfaces of the cusps are smooth and the ventricular surfaces are rough and furnish attachment to the chordae tendinae.
• The valves are folds of endocardium strengthened by fibrous tissue and having muscular tissue at the periphery.
• Each cusp receives chordae tendinae from two papillary muscles. Of the latter, two are on the septum and the third and the largest springs from the anterior wall.
• The pulmonary orifice is circular and is situated at the summit of the conus arteriosus.
• It is guarded by the pulmonary valve composed of three semilunar cusps, one medial (anterior), one lateral (anterior) and the third is posterior.
• The cusps are very thin and almost transparent. Each segment has two borders and two surfaces.
• The attached borders are thick.
• The free borders are concave, thin and nearly straight when tensed. This border of each cusp sometime presents at its middles a small fibrocartilagenous thickening, the corpus Aurantii. The superior surface is concave raised and laid against the walls of the vessel when the ventricle contracts.
• The inferior or ventricular surface is convex which is directed towards the blood when the ventricle contracts.
• A crest-the crista supraventricularis separates cavity of the conus arteriosus from the atrio-ventricular orifice.