What are the sinuses? How many do we have?
A sinus is a hollow, air-filled cavity. For the purposes of this article, a sinus will refer to those hollow cavities that are in the skull and connected to the nasal airway by a narrow hole in the bone (ostium). Normally all sinuses are open to the nasal airway through an ostium. Humans have four pair of these cavities each referred to as the:
- Frontal sinus (in forehead),
- Maxillary sinus (behind cheeks),
- Ethmoid sinuses (between the eyes), and
- Sphenoid sinus (deep behind the ethmoids)
The four pair of sinuses are often described as a unit and termed the “paranasal sinuses.” The cells of the inner lining of each sinus are mucus-secreting cells, epithelial cells and some cells that are part of the immune system (macrophages, lymphocytes, and eosinophils).BOOK AN APPOINTMENT