Skip to content
My WebMD Sign In, Sign Up

Allergies Health Center

Image Collection:

Human Anatomy

Picture of the Human Sinuses

Picture of the Sinuses

back buttonnext button

© 2009 WebMD, LLC. All rights reserved.

The sinuses are a connected system of hollow cavities in the skull. The largest sinus cavities are around an inch across; others are much smaller. The sinus cavities include:

• The maxillary sinuses (the largest), in the cheekbones.
• The frontal sinuses, in the low-center of the forehead.
• The ethmoid sinuses, between the eyes, at the nasal bridge.
• The sphenoid sinuses, in bones behind the nasal cavity.

The sinuses are lined with soft, pink tissue called mucosa. Normally, the sinuses are empty except for a thin layer of mucus.

The inside of the nose has ridges called turbinates. Normally these structures help humidify and filter air. The nose is divided in the center by a thin wall, called the septum. Most of the sinuses drain into the nose through a small channel or drainage pathway called the middle meatus.

The purpose of the sinuses is unclear. One theory is that sinuses help humidify the air we breathe in; another is that they enhance our voices.

Today on WebMD

epinephrine at school
Article
Woman sneezing with tissue in meadow
Slideshow
 
Woman wth tissue
Slideshow
thumbnail_florist_wearing_surgical_mask
Slideshow
 

woman sneezing
Slideshow
Bottle of allergy capsules and daisies
Article
 
Urban blossoms
Slideshow
Woman blowing nose
Slideshow
 

Woman with itchy watery eyes
Slideshow
Allergy prick test
VIDEO
 
Man sneezing into tissue
Tools
woman with duster crinkling nose
Quiz