Biological tissue

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.

The cells within a tissue share a common embryonic origin. Microscopic observation reveals that the cells in a tissue share morphological features and are arranged in an orderly pattern that achieves the tissue’s functions. From the evolutionary perspective, tissues appear in more complex organisms. For example, multicellular protists, ancient eukaryotes, do not have cells organized into tissues.

Although there are many types of cells in the human body, they are organized into four broad categories of tissues: epithelial, connective, muscle, and nervous. Each of these categories is characterized by specific functions that contribute to the overall health and maintenance of the body. A disruption of the structure is a sign of injury or disease. Such changes can be detected through histology, the microscopic study of tissue appearance, organization, and function.

Plant tissue

Plant tissue is a characteristic tissue of cormophytic plants. It is possible to recognize two main types of plant tissues: meristematic (or embryonic) and permanent (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.

Animal tissue

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:

  • epithelial tissue;
  • connective tissue;
  • muscle tissue;
  • nervous tissue.

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