The lungs contain a variety of cell types, each with a specific function. The primary type of cell in the respiratory epithelium is ciliated pseudostratified columnar epithelium, which consists of the following five cell types:
- Ciliated cells: These cells are responsible for moving mucus and debris out of the airways, preventing them from reaching the alveoli.
- Goblet cells: These cells produce mucus, which traps inhaled particles and helps to protect the lungs from infection.
- Basal cells: These cells are stem cells that can differentiate into other cell types in the respiratory epithelium.
- Brush cells: These cells have microvilli, which increase their surface area and are thought to be sensory receptors.
- Neuroendocrine cells: These cells secrete hormones and neurotransmitters that regulate airway function.
In addition to these epithelial cells, the lungs also contain several other cell types, including:
- Alveolar epithelial cells: These cells line the alveoli, the tiny air sacs where gas exchange takes place. There are two types of alveolar epithelial cells: type I pneumocytes and type II pneumocytes. Type I pneumocytes are thin and flat and are responsible for gas exchange. Type II pneumocytes are cuboidal and secrete surfactant, a substance that reduces surface tension in the alveoli, preventing them from collapsing.
- Fibroblasts: These cells produce collagen and other extracellular matrix components that provide structural support to the lungs.
- Smooth muscle cells: These cells surround the airways and blood vessels, helping to regulate airflow and blood flow.
- Macrophages: These cells engulf and destroy foreign particles, such as bacteria and dust.
- Mast cells: These cells release histamine and other inflammatory mediators, contributing to allergic responses.
