A trabecula (plural trabeculae, from Latin for "small beam") is a small, often microscopic, tissue element in the form of a small beam, strut or rod, generally having a mechanical function, and usually composed of dense collagenous tissue (such as the trabecula of the spleen.) They can be composed of other materials; in the heart, for example, muscles such as trabeculae carneae and septomarginal trabecula form similar structures. The formation of trabeculae is known as trabeculation.