tectum

Tectum is a term used in biology to denote a roof-like structure that covers or lies at the top of a larger organ. Its use varies across disciplines, but it most commonly refers to a dorsal portion of the brain in vertebrates and to a surface layer in pollen biology. The word derives from Latin tectum, meaning roof or covering.

In vertebrate neuroanatomy, the tectum refers to the dorsal part of the midbrain (the mesencephalon). It comprises two paired structures: the superior colliculus and the inferior colliculus. In many non-mammalian vertebrates, the superior colliculus is referred to as the optic tectum due to its role in processing visual information. In mammals, the superior colliculus handles visual processing and reflexive orienting movements of the eyes and head, while the inferior colliculus is a major relay in the auditory pathway and contributes to sound localization and reflex responses. The tectum receives sensory inputs from the retina and auditory pathways and projects to thalamic and cortical areas, participating in multisensory integration and reflexive behavior.

In botany and palynology, the tectum is the outermost layer of the pollen exine, forming the protective roof over the pollen grain. It is often sculptured and varies in continuity and ornamentation among taxa. The tectum rests on a framework of columellae, and the exine’s structure—such as whether the tectum is continuous (tectate) or partially exposed—helps distinguish pollen types in taxonomic and paleobotanical studies.

Etymology traces to Latin tectum, meaning roof or covering, a sense reflected in the various uses of the term across biology.