A trabecula is a small, often microscopic, tissue element in the form of a small beam, strut or rod that supports or anchors a framework of parts within a body or organ. A trabecula generally has a mechanical function, and is usually composed of dense collagenous tissue. It can be composed of other material such as muscle and bone. In the heart, muscles form trabeculae carneae and septomarginal trabeculae. Cancellous bone is formed from groupings of trabeculated bone tissue.

The trabeculae carneae are rounded or irregular muscular columns which project from the inner surface of the right and left ventricle of the heart. These are different from the pectinate muscles, which are present in the atria of the heart. In development, trabeculae carneae are among the first of the cardiac structures to develop in the embryonic cardiac tube. Further, throughout development some trabeculae carneae condense to form the myocardium, papillary muscles, chordae tendineae, and septum.