The trabeculae carneae (columnae carneae, or meaty ridges), are rounded or irregular muscular columns which project from the inner surface of the right and left ventricles of the heart. These are different from the pectinate muscles, which are present in the right atrium and the atrial appendages of the heart.
There are two kinds:
- some are attached along their entire length on one side and merely form prominent ridges,
- others are fixed at their extremities but free in the middle (Moderator bands/septomarginal trabeculae).
The purpose of the trabeculae carneae is most likely to prevent suction that would occur with a flat surfaced membrane and thus impair the heart's ability to pump efficiently.
The trabeculae carneae also serve a function similar to that of papillary muscles in that their contraction pulls on the chordae tendineae, preventing inversion of the mitral (bicuspid) and tricuspid valves, that is, their bulging towards the atrial chambers, which would lead to subsequent leakage of the blood into the atria. So by the action of papillary muscles on the atrioventricular valves, backflow of the blood from the ventricles into the atria is prevented.
The moderator bands carry the right branch of the AV bundle and are part of the conducting system of the heart.
The pectinate muscles (musculi pectinati) are parallel ridges in the walls of the atria of the heart. They are so-called because of their resemblance to the teeth of a comb as in pectin.
Behind the crest (crista terminalis) of the right atrium the internal surface is smooth. Pectinate muscles make up the part of the wall in front of this, the right atrial appendage.
In the left atrium, the pectinate muscles, fewer and smaller than in the right atrium, are confined to the inner surface of its atrial appendage. This is due to the embryological origin of the auricles, which are the true atria. Some sources cite that the pectinate muscles are useful in increasing the power of contraction without increasing heart mass substantially.
Pectinate muscles of the atria are different from the trabeculae carneae which are found on the inner walls of both ventricles. The pectinate muscles originate from the crista terminalis
