What is a tissue?
A tissue is a group of similar cells, together with their supporting material, that work together to perform a particular function. In the human body, tissues combine to form organs and organ systems.
Main types of human tissue
| Type | Main features | Examples and functions |
|---|---|---|
| Epithelial tissue | Cells are closely packed and cover surfaces. | Protects the skin, lines airways and the digestive tract, and may absorb or secrete substances. |
| Connective tissue | Cells are separated by an extracellular material. | Binds and supports structures; includes bone, cartilage, blood, lymph, fat, and tendons. |
| Muscle tissue | Specialised cells contract. | Produces movement; includes skeletal, smooth, and cardiac muscle. |
| Nervous tissue | Contains cells adapted to transmit electrical signals. | Detects stimuli and coordinates responses through the brain, spinal cord, and nerves. |
Epithelial tissue
Epithelial cells form protective coverings and linings. Simple epithelium has one cell layer and is suitable for absorption, secretion, or filtration. Ciliated epithelium has cilia that move materials, such as mucus, along a surface. Stratified epithelium has several layers and provides stronger protection.
Connective tissue
Bone provides support and protection. Cartilage provides flexible support at joints and in structures such as the nose and ear. Blood transports substances, while lymph returns excess tissue fluid to the circulation and contributes to defence. Adipose tissue stores energy and insulates the body.
Muscle and nervous tissue
Skeletal muscle is usually under conscious control and moves bones. Smooth muscle contracts in the walls of organs such as the intestine. Cardiac muscle contracts rhythmically in the heart. Nervous tissue receives information and transmits impulses for coordination.
Revision questions
- Define a tissue.
- Name the four main types of human tissue.
- Give one function of epithelial, connective, muscle, and nervous tissue.
- Distinguish between skeletal, smooth, and cardiac muscle.
