Tunica (biology)

: tunicae) is a layer, coat, sheath, or similar covering.

In modern biology in general, tunica occurs as a technical or anatomical term mainly in botany and zoology.

It usually refers to membranous structures that line or cover particular organs.

As an anatomical or morphological reference in zoology, tunica has a range of applications to membranous structures in anatomy, including human anatomy.

Such structures are generally coverings or capsules of organs, but also may be linings of cavities.

A coloured illustration showing three two layers over a hump, with arrows pointing out the outer layers.
The outer layer of cells of an apical meristem. This is known as the tunica.