MARIAN MILLER / SCIENCE PHOTO LIBRARY MARIAN MILLER / SCIENCE PHOTO LIBRARY
Coloured transmission electron micrograph (TEM) of a section through part of a type II alveolar cell from an old guinea pig (Cavia porcellus). The nucleus (blue), which contains the cell's genetic information, is at bottom right. The green area in the nuclear membrane is a nuclear pore. This cell is found in the alveoli (air sacs) of the lungs. It secretes surfactant, a substance that reduces surface tension in the air sac and prevents it from collapsing.
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