Tissue Definition and Examples in Biology

In biology, a tissue is a group of cells and their extracellular matrix that share the same embryonic origin and perform a similar function. Multiple tissues then form organs. The study of animal tissues is called histology, or histopathology when it is concerned with diseases. The study of plant tissues is called plant anatomy. The word "tissue" comes from the French word "tissu," which means "woven." French anatomist and pathologist Marie François Xavier Bichat introduced the term in 1801, stating that body functions could be understood better if they were studied at the level of tissues rather than organs.

Animal Tissues

There are four basic tissues in humans and other animals: epithelial tissue, connective tissue, muscle tissue, and nervous tissue. The embryonic tissue (ectoderm, mesoderm, endoderm) from which they derive sometimes varies, according to species.

Epithelial Tissue

Cells of epithelial tissue form sheets that cover the body and organ surfaces. In all animals, most epithelium derives from the ectoderm and endoderm, except the epithelium, which derives from the mesoderm. Examples of epithelial tissue include the skin surface and the linings of the airways, reproductive tract, and gastrointestinal tract. There are several kinds of epithelium, including simple squamous epithelium, simple cuboidal epithelium, and columnar epithelium. Functions include protecting organs, eliminating waste, absorbing water and nutrients, and secreting hormones and enzymes.

Connective Tissue

Connective tissue consists of cells and non-living material, called the extracellular matrix. The extracellular matrix may be either fluid or solid. Examples of connective tissue include blood, bone, adipose, tendons, and ligaments. In humans, cranial bones derive from the ectoderm, but the other connective tissues come from the mesoderm. Functions of connective tissue include shaping and supporting organs and the body, allowing body movement, and providing oxygen diffusion.

Muscle Tissue

The three types of muscle tissue are skeletal muscle, cardiac muscle, and smooth (visceral) muscle. In humans, muscles develop from the mesoderm. Muscles contract and relax to allow body parts to move and blood to pump.

Nervous Tissue

Nervous tissue is divided into the central nervous system and peripheral nervous system. It includes the brain, spinal cord, and nerves. The nervous system derives from the ectoderm. The nervous system controls the body and communicates between its parts.

Plant Tissues

There are three tissue systems in plants: epidermis, ground tissue, and vascular tissue. Alternatively, plant tissues may be categorized as either meristematic or permanent.

Epidermis

The epidermis consist of cells that coat the outer surface of leaves and the bodies of young plants. Its functions include protection, waste removal, and nutrient absorption.

Vascular Tissue

Vascular tissue is akin to blood vessels in animals. It includes the xylem and phloem. Vascular tissue transports water and nutrients within a plant.

Ground Tissue

Ground tissue in plants is like connective tissue in animals. It supports the plant, manufactures glucose via photosynthesis, and stores nutrients.

Meristematic Tissue

Actively dividing cells are meristematic tissue. This is the tissue that allows a plant to grow. The three types of meristematic tissue are apical meristem, lateral meristem, and intercalary meristem. Apical meristem is the tissue at stem and root tips that increases stem and root length. Lateral meristem includes tissues that divide to increase the diameter of a plant part. Intercalary meristem is responsible for the formation and growth of branches.

Permanent Tissue

Permanent tissue encompasses all cells, living or dead, that have stopped dividing and maintain a permanent position within a plant. The three types of permanent tissue are simple permanent tissue, complex permanent tissue, and secretory (glandular) tissue. Simple tissue is further divided into the parenchyma, collenchyma, and sclerenchyma. Permanent tissue provides support and structure for a plant, helps manufacture glucose, and stores water and nutrients (and sometimes air).

Sources

• Bock, Ortwin (2015). "A history of the development of histology up to the end of the nineteenth century." Research. 2:1283. doi:10.13070/rs.en.2.1283
• Raven, Peter H.; Evert, Ray F.; Eichhorn, Susan E. (1986). Biology of Plants (4th ed.). New York: Worth Publishers. ISBN 0-87901-315-X.
• Ross, Michael H.; Pawlina, Wojciech (2016). Histology : A Text and Atlas : With Correlated Cell and Molecular Biology (7th ed.). Wolters Kluwer. ISBN 978-1451187427.