A biological tissue is an ensemble of similar cells and their extracellular matrix, characterized by similar structure and functions. Tissues represent the next level of organization after cellular organization; in practice, they are formed by cells of the same type that associate together to perform a common function. Each tissue therefore possesses one or more of its own specific functions, different from those of other tissues.
The English word “tissue” derives from the French word “tissue”, meaning that something that is “woven”, from the past participle of the verb tisser, “to weave”.
The science that studies tissues is histology, which is an important branch of medicine and biology. To study tissues, biologists use mainly microscopes, optical and electronic, as well as techniques of molecular biology and genetics. Tissues are solid, but also liquid, such as blood and lymph.
Plant tissue is a characteristic tissue of cormophytic plants. It is possible to recognize two main types of plant tissues: meristematic (or embryonic) and definitive (or adult). The meristematic tissues are formed by cells that have the characteristic of being “totipotent” that is to have the ability to generate up to an entire individual.
There are four basic types of biological tissues present in all animals, from humans to the simplest invertebrates (excluding porifera and placozoa in which the nervous tissue and muscle tissue are missing). These tissues are in turn divided into sub-types, more specialized, and, in higher animals, go to make up the different organs. They are: