Epitheliomuscular Cells (Skin-and-Muscle Cells)

Skin on top, muscle underneath

A hydra is a tiny animal that lives in ponds. It's about as long as your fingernail. It has a tube-shaped body and a ring of tentacles around its mouth. It's a cousin of jellyfish and sea anemones.

The outside of a hydra is covered with epitheliomuscular cells. Each one is shaped like a column standing side by side with its neighbors.

• The top part is like a skin cell. It covers and protects the hydra.
• The bottom part has long muscle tails that can squeeze.

Covering and moving

The muscle tails all point the same way, along the hydra's body. When they squeeze together, the hydra gets shorter. If something bumps it, a hydra can pull itself into a small ball in a flash!

These cells help the hydra bend, wave its tentacles, and even move to a new spot. In your body, skin cells and muscle cells are different cells. In a hydra, one cell does both.

Epitheliomuscular cell quiz