Tissue

Tissue is the name for a group of similar cells that have a common structure and function and which work together. Tissues fit together to form organs in higher animals These animals have four basic types of tissue.

The animal body is made up of many different kinds of cells. These specialize to perform certain functions, or specific tasks. A group of closely associated or similar cells that work together to do one thing is called a tissue. All the cells in a tissue look very similar and all do the same work.

TYPES OF TISSUE

There are four types of animal tissue: epithelial, connective, muscle, and nervous tissue. Every cell in each of these tissues is an independent unit, yet all of the cells in a given tissue interact with one another. They must do this in order to perform a certain necessary function for the animal's body. For example, an animal's brain is made of nerve tissue that is composed of millions of connected nerve cells. In animals, when two or more tissues are associated and work together, they form an organ such as the stomach or the heart.

The same is true for plants, except they have only three types of tissue. Plant tissue, like animal tissue, is also organized into organs, so that epidermal plant tissue makes up the organ known as a leaf. For both plants and animals, a tissue is the "stuff," or specific type of cellular material, out of which specialized organs are made.

HUMAN TISSUE

As animals, humans have four different types of tissues: epithelial, connective, muscle, and nervous tissue.

Epithelial Tissue. The epithelial tissue, whose closely packed cells make it ideal for forming a lining or a covering, is what makes up the skin. This tissue also makes up the lining for the organs and the many passageways. Because its cells are so tightly packed together, it allows the skin to be an excellent barrier and protects the body against injury and invading microorganisms (any form of life that is too small to be seen without a microscope). It also regulates fluid loss.

Nervous Tissue. The nervous tissue is made up of cells called neurons. These are designed to carry impulses. This highly specialized tissue carries electrical signals from one part of the body to another and allows it to function as an organized unit.

Muscle Tissue. Muscle tissue is responsible for producing movement. Its cells are designed to work by contracting and relaxing. They also are built to respond to stimuli transmitted by neurons. There are three types of muscle tissue. Smooth muscle makes up organs that people do not control, such as the intestines. Striated, or skeletal muscle, is under people's control and makes up the muscles that allow people to move. Cardiac muscle is also called heart muscle and is responsible for the regular and powerful contraction of the heart. Unlike skeletal muscle, it never needs to rest.

Connective Tissue. Finally, connective tissue is the most common tissue in the body, and it is what holds the entire body together. Bone, cartilage, and blood are made of connective tissue. Bone is a type of mineralized connective tissue, cartilage is found between joints, and blood is considered to be a connective tissue in liquid form since it circulates throughout the body.

PLANT TISSUE

Plants have three types of tissue. Their epidermal tissue serves a purpose similar to humans, in that it covers the surfaces of leaves, stems, and roots and protects its inner parts. The tissue through which a plant transports materials is called its vascular tissue. Its cells are elongated and form tubelike organs. The rest of a plant is made up of what is called fundamental plant tissue. In plants and animals then, tissues are the intermediary stage between an organism's individual cells and its specialized organs. Therefore, cells are arranged into groups, called tissues, and tissues are eventually grouped into organs.

[See alsoCell; Organ ]

Tissue

A tissue is a collection of similar cells grouped to perform a common function. Different tissues are made of their own specialized cells that are adapted for a given function.

All animal cells are basically similar. Each cell has a cell wall or plasma membrane that surrounds the cell and contains various receptors that interact with the outside area. A nucleus, Golgi apparatus, mitochondria, and other structures are contained in each cell. Beyond that, cells are specialized in structure for a given function.

The study of tissues is called histology. Studying the structure of tissue is done by staining a thin specimen of the tissue and placing it under a microscope . An experienced histologist can look at a specimen and immediately determine from which organ it was taken. A histologist can also see and diagnose a disease if it is present in the tissue. The study of disease processes is called pathology .

Tissues are divided by function into a number of categories. Muscle tissue, for example, makes up the muscles of the body. A muscle belongs to one of three categories-voluntary muscle which can be controlled for movement or lifting, involuntary muscle which is not under conscious control (such as the muscle tissue in the digestive organs), and cardiac muscle which forms the heart .

Connective tissues compose the bones, tendons, and ligaments that make up the support of the body. The body also consists of adipose tissue or fat .

Nervous tissue forms the brain , spinal cord, and the nerves that extend through the body. Digestive tissue is found in the digestive system including the stomach, intestines, liver, pancreas, and other organs involved in digestion. Vascular tissue comprises the blood-forming portion of the bone marrow and the blood cells themselves. Epithelial tissue forms sheets that cover or line other tissues. The skin and the lining of the stomach are both examples of epithelial tissue. Various reproductive tissues form the ovaries, testes and the resulting gametes (ova and sperm).

Combined, these tissues form the human body and carry out its functions.

Tissue

A tissue is a collection of similar cells grouped to perform a common function. Different tissues are made of their own specialized cells that are adapted for a given function.

All animal cells are basically similar. Each cell has a cell wall or plasmamembrane that surrounds the cell and contains various receptors that interact with the outside area. A nucleus, Golgi apparatus, mitochondria, and other structures are contained in each cell. Beyond that, cells are specialized in structure for a given function.

The study of tissues is called histology. Studying the structure of tissue is done by staining a thin specimen of the tissue and placing it under a microscope. An experienced histologist can look at a specimen and immediately determine from which organ it was taken. A histologist can also see and diagnose a disease if it is present in the tissue. The study of disease processes is called pathology.

Tissues are divided by function into a number of categories. Muscle tissue, for example, makes up the muscles of the body. A muscle belongs to one of three categories-voluntary muscle which can be controlled for movement or lifting, involuntary muscle which is not under conscious control (such as the muscle tissue in the digestive organs), and cardiac muscle which forms the heart.

Connective tissues compose the bones, tendons, and ligaments that make up the support of the body. The body also consists of adipose tissue or fat.

Nervous tissue forms the brain, spinal cord, and the nerves that extend through the body. Digestive tissue is found in the digestive system including the stomach, intestines, liver, pancreas, and other organs involved in digestion. Vascular tissue comprises the blood-forming portion of the bone marrow and the blood cells themselves. Epithelial tissue forms sheets that cover or line other tissues. The skin and the lining of the stomach are both examples of epithelial tissue. Various reproductive tissues form the ovaries, testes and the resulting gametes (ova and sperm).

Combined, these tissues form the human body and carry out its functions.

Tissue

A tissue is made up of a group of cells that usually look similar to one another and come from the same region in a developing embryo. The group of cells that make up a tissue have physiological functions that work together in a coordinated way to support special functions. The special function of a tissue is also influenced by the kind of material that surrounds the tissue and by communication among the cells of the tissue. Different kinds of tissue have different physical properties. Tissues may be hard (bone), soft (muscle), or even liquid (blood).

In the structural organization of the body, tissues are located between the cell and organ levels of organization. Individual cells are a lower level of organization. Tissues are made up of many individual cells. Groups of different kinds of tissues are organized together to form organs, which have special functions with characteristic shapes and functional properties.

There are four kinds of tissues based on differences in their anatomy and function: epithelial tissue, connective tissue, muscle tissue, and nervous tissue. Epithelial tissue is made of layers of cells that are joined together and may cover the surface of the body (epidermis of the skin), line spaces in the body (lining of the abdominal cavity) and hollow structures (lining of blood vessels), or form glands (sweat glands). Connective tissue is usually made of cells and extracellular fibers that hold structures together (tendons), protect them (cartilage), store energy (fat), or produce blood.

Muscular tissue is made of cells that are organized to shorten and produce force when they contract (smooth skeletal and cordine muscle). Nervous tissue is made of neurons and accessory cells. Neurons are the cells that carry information in the form of electric action potentials . Accessory cells protect and support the function of neurons.

see also Blood; Connective Tissue; Epithelium; Muscle; Nervous Systems; Neuron; Organ; Skin

Michael G. Scott

Bibliography

Tortora, Gerard J., and Sandra R. Grabowski. Principles of Anatomy and Physiology. New York: John Wiley & Sons, Inc., 2000.

tis·sue / ˈtishoō/ • n. 1. any of the distinct types of material of which animals or plants are made, consisting of specialized cells and their products: inflammation is a reaction of living tissue to infection or injury| (tissues) the organs and tissues of the body.2. tissue paper. ∎  a disposable piece of absorbent paper, used esp. as a handkerchief or for cleaning the skin. ∎  rich or fine material of a delicate or gauzy texture: [as adj.] the blue and silver tissue sari. 3. [in sing.] an intricate structure or network made from a number of connected items: such scandalous stories are a tissue of lies.DERIVATIVES: tis·su·ey adj. (in sense 2).