Tissue (biology)

Emphysema H and E

Stem-histology-cross-section-tag

Plant cell type collenchyma

Xylem rays (Tilia Americana)

Skeletal muscle - cross section, nerve bundle

Pierre-Maximilien Delafontaine - Portrait of Marie François Xavier Bichat

Tissue in biology refers to a group of cells that have similar structure and function together to perform a specific activity. Histology is the science that studies tissues. There are four basic types of tissue in the body of all animals, including humans: epithelial tissue, connective tissue, muscle tissue, and nervous tissue. Each type of tissue has a distinct role in the body, and the combination of tissues forms organs which perform the complex functions necessary for life.

Types of Tissue

Epithelial Tissue

Epithelial tissue covers the body surfaces, lines body cavities, and forms glands. It serves as a barrier against microbial invasion, regulates the exchange of materials, and is involved in absorption and secretion. Epithelial tissue is classified by the shape of cells (squamous, cuboidal, columnar) and the number of cell layers (simple, stratified, pseudostratified).

Connective Tissue

Connective tissue supports, binds together, and protects tissues and organs of the body. It consists of cells embedded in a large amount of extracellular matrix. Types of connective tissue include bone, cartilage, adipose (fat) tissue, blood, and lymph. Each has a distinct composition and function.

Muscle Tissue

Muscle tissue is responsible for producing force and causing motion, either locomotion or movement within internal organs. Muscle tissue can be classified into three types: skeletal, cardiac, and smooth muscle. Skeletal muscle is under voluntary control, while cardiac and smooth muscle movements are controlled involuntarily.

Nervous Tissue

Nervous tissue is composed of neurons and supporting cells called neuroglia. Neurons are the primary type of cell that most people associate with the nervous system. They are responsible for sensing stimuli and transmitting signals to and from different parts of an organism. Neuroglia provide support and protection for neurons.

Functions of Tissues

Tissues work together in the body to perform complex functions. For example, the heart is made up of muscle tissue that contracts to pump blood, connective tissue that provides the heart with structure and support, epithelial tissue that lines the blood vessels, and nervous tissue that regulates the heartbeat.

Regeneration and Repair

Tissues have varying abilities to regenerate (replace damaged cells with new cells) and repair (heal damaged tissue). Epithelial tissue and most types of connective tissue have a high capacity for regeneration and repair. Muscle and nervous tissues, however, have a limited ability to regenerate, which is why injuries to these tissues are often more serious and take longer to heal.

Study of Tissues

The study of tissues, known as histology, involves examining thin slices of tissue under a microscope. Histological studies are crucial for understanding the structure and function of tissues, as well as diagnosing diseases that affect tissue structure.