Glossary
tissue
A tissue is a group of similar cells with a shared job and the material between them — the level between a cell and an organ.
A tissue is a group of similar cells that share a job, together with the material between them. It is the level between a cell and an organ: cells of one kind, arranged to do one thing, are a tissue; several tissues arranged to do a bigger thing are an organ. Four kinds cover the body. Epithelial tissue covers and lines. Muscle tissue contracts. Nervous tissue conducts. Connective tissue holds parts together, stores fat and carries substances. When a question asks what level a structure sits at, the test is whether the answer names one job done by one kind of cell. Skin is an organ, not a tissue, because it carries epithelium, connective tissue, muscle and nerve at once. The same rule explains why one cell type can repair itself without rebuilding the others.
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Related terms
- epithelial tissue — Epithelial tissue covers and lines surfaces, forms glands, and sits on a basement membrane — it has no blood vessels of its own.
- muscle tissue — Muscle tissue shortens to produce movement, and its three kinds — skeletal, smooth and cardiac — differ in where they are and whether they obey you.
- nervous tissue — Nervous tissue carries electrical signals: neurons generate and conduct them, and glial cells insulate, feed and support the neurons.
- homeostasis — Homeostasis is the maintenance of a stable internal environment while conditions outside the body change — a loop that keeps correcting, not a fixed state.
- dermis — The dermis is the layer under the epidermis: connective tissue carrying the blood vessels, nerves, glands and hair follicles the skin needs.
Source: The anatomy and physiology guide in this course, whose organ and tissue descriptions follow the US National Cancer Institute's SEER Training Modules and MedlinePlus consumer health pages. Both are US federal government material, not subject to copyright in the United States. The definition above is written for this course in our own words. (SEER Training Modules accessed 2026-10-26; definition written 2026-10-27)