2. Tissues
Tissues are groups of different specialised cells that work together to create groups of cells that have a specific purpose. Tissues join together, forming organs. The surface epithelium, an example of tissue found in the lung, is formed of millions of epithelial cells.
Another example is alveolar cells, which form alveoli, which is surrounded by capillaries. We'll learn more about this later in the course.
Let's consolidate your knowledge so far with a quiz.