Human Body Tissues: Types and Functions

What is a Tissue?

A tissue is an aggregate of connected cells that have a similar origin, structure, and function and cooperate to perform a certain function.

Epithelial Tissue

Epithelial tissue covers the body and organ surfaces, lines body cavities, and forms glands. It is involved with protection, absorption, and excretion.

It is made of one or more layers of cells arranged without spaces between them. They can be different shapes—such as flat, prismatic, or cubic—and be arranged in one or more different layers.

Functions of Epithelial Tissue

Epithelia line or cover your body surface, your organs, and all your body cavities, such as your digestive tract, your lungs, blood vessels, and bladder to protect them. Quite often, they perform other functions such as:

• Absorption of substances (e.g., medicines)
• Excretion (e.g., in sweat)
• Diffusion (gases in lungs)
• Filtration (in kidneys)

Connective Tissue

Connective tissue binds, supports, and protects body parts, while storing energy and minerals. Connective tissues support the softer organs of the body against gravity and connect the parts of the body together. They also store fat reserves and produce the cells of the blood. Connective tissue joins and links the other tissues to each other.

Types of Connective Tissue

• Fibrous or dense: It forms tendons and ligaments which join muscles and bones.
• Loose or areolar: Surrounding other internal organs and under the skin.
• Elastic: It surrounds organs that have to change shape or size regularly, such as the stomach, arteries, and lungs.

Muscle Tissue

Muscle tissue contracts to produce movement. It consists of tightly packed, long-shaped cells called muscle fibers, which are specialized to shorten or contract, resulting in movement of some kind.

Three Types of Muscle Tissue

• Skeletal muscle tissue: Connects to tendons, which attach to bones. They can be contracted voluntarily and fast to cause certain body parts to move.
• Cardiac muscle tissue: Found only in the heart. Cells are much shorter than in the skeletal muscle and they can contract rhythmically on their own.
• Smooth muscle tissue: This is also involuntary; we cannot control its contractions consciously.

Nervous Tissue

Nervous tissue initiates and transmits nerve impulses that coordinate body activities. It is composed of neurons, cells specialized for generating and transmitting electrical impulses throughout the body.

It forms a rapid communication network for the body, capable of detecting stimuli, transmitting the information to the brain, and sending orders to the effectors. Nervous tissue is located in the brain, the spinal cord, and the nerves. Nervous tissue also includes another type of cells called glial cells, which do not transmit impulses.