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How do integuments differ between unicellular organisms and multicellular animals?

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A pangolin walks through grass with a blue circle around it and the word endangered written in white across the image. — Integument The pangolin is the only mammal in the world covered in scales.

The integument serves as the boundary between an organism and its environment, but its structure varies significantly between unicellular and multicellular organisms.1

Unicellular Organisms

In unicellular organisms, such as bacteria and protozoans, the integument consists of the cell membrane and any secreted coatings produced by the cell. Many bacteria also possess an external cell wall that provides structural support and protection.12

Multicellular Animals

In contrast, multicellular animals possess an integument composed of specialized epithelial cells, often organized into layers.12
* Invertebrates: The integument typically consists of a single or multiple layers of epithelial cells, which may secrete various coatings, such as the cuticle found in insects. Some invertebrates also develop rigid skeletal materials or exoskeletons.12
* Vertebrates: The integument has evolved into a complex organ system comprising the epidermis and an underlying dermis. This system includes diverse derivatives such as scales, feathers, hair, and various glands, which provide critical adaptations for survival in terrestrial and aquatic environments.1345