The Four Sets of Sinuses

Maxillary Sinuses: located in the maxillary portion of the facial bones. These sinuses are located under the eyes and are usually the largest of all the sinuses. They are present at birth and grow in size with facial growth.

Ethmoid Sinuses: located in the ethmoid portion of the facial bones. These sinuses are located between the eyes. These sinuses have an anterior and posterior portion to them as well as many partitions that separate them into many partitions. Looking into these sinuses is much like looking into a honeycomb. Like the maxillary sinuses, these sinuses are present at birth.

Sphenoid Sinuses: located in the sphenoid bone. This bone is located midline in the skull, deep behind the nose. This sinus is usually divided in half by a midline septum. At birth it is usually filled with bone marrow, and starts to become air filled sometime later in life.

Frontal Sinuses: located in the frontal bone, which lies in the forehead area of the skull. These sinuses can grow to be quite large in the adolescent years, but are usually not present at birth. Most children begin to develop these sinuses around 10 to 14 years of age. They can remain quite small, or become very large, especially in males. About 10% of the population does not develop frontal sinuses.