Covering and lining
Your skin keeps bath water out. Yet sweat comes out. How?
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Step 1 of 3
- A surface needs a covering.
- Epithelial cells pack edge to edge, with very little space.
- The cells hold together, all along the row.
Packed skin cells keep water out, but sweat leaves through tiny pores.
Rule
Epithelial tissue covers the body and lines the organs inside. Its cells are packed close, and its shape fits its job.
- Epithelial tissue — the covering and lining tissue.
Exchange is letting gases and other things pass across. Absorption is taking in digested food. Secretion is releasing fluids. A gland makes and releases a fluid.
| Job | Cells | Place |
|---|---|---|
| Exchange | One thin, flat layer | Lungs, blood vessels |
| Protection | Many layers | Skin, mouth |
| Absorption | One layer of tall cells | Small intestine |
| Secretion | Cells that release fluids | Salivary and sweat glands |
A thin layer lets gases cross fast. That is why the lung lining is one layer thick. Sweat glands release sweat through tiny pores.