Anatomy & Organs

Paranasal sinuses – structure, function & diseases

Paranasal sinuses

The sinuses are air-filled cavities within the bony structure of the skull. The most common complaint is sinusitis , which is associated with pain and a runny nose, but usually subsides after 10 days

What are the sinuses?

The sinuses are spaces within the bone structure of the skull and face that are filled with air. These free cavities are used to warm and humidify the air we breathe, and as a resonator for the voice.

In addition, the paranasal sinuses reduce the weight of the skull, which would be significantly heavier without these cavities. The inner walls of the paranasal sinuses are covered with cells that secrete a moist secretion. This catches pathogens in the air before they get into the body and prevents the inside of the nose from drying out.

The paranasal sinuses are divided into four pairs. One pair behind the nostrils, one above the eyes, one between the eyes, and one cavity each behind the ethmoids. Often referred to just as “sinuses”, however, the paranasal sinuses are just one type of sinus cavity in the human body.

Anatomy & Structure

Humans have four different pairs of paranasal oils: the maxillary, frontal, sphenoid and ethmoid cells. The maxillary sinus is below the eyes in the maxillary bone.They are the largest paranasal sinuses and the first to develop in the growing organism. The frontal sinus is located in the frontal bone above the eyes. It forms after the second year of life and continues to grow into puberty. The sphenoid sinus forms in the center of the skull within the sphenoid bone and continues to grow into early adulthood.

The ethmoid cells form several small air cells between the eyes. They are filled with fluid at birth and continue to grow until the age of 12. They are shaped like small pyramids and separated by thin septa.

Functions & Tasks

The full functions of the paranasal sinuses are still debated, but some roles are conjectured. They reduce the overall weight of the human head, especially the front area and facial bones.

They improve the resonance of the voice. Paranasal sinuses can act as a kind of buffer against impacts to the face. The cavities insulate sensitive nerve tracts of the teeth or eyes from temperature fluctuations in the incoming respiratory air. They humidify and warm incoming air because airflow is slowed down in these regions. The paranasal sinuses regulate the pressure equalization of the intranasal area.

They also fulfill an important function within the immune system by being able to intercept pathogens before they enter the respiratory tract. Aside from these assumptions about the function of the paranasal sinuses, it is also possible that they do not serve any direct biological function. That is, they may also be a spandrel (by-product) of actual biological adaptation that occurred during evolutionary development.


The most common complaint that can occur in connection with the paranasal sinuses is sinusitis . It is caused by allergies , infections or other autoimmune disorders.In most cases, it is caused by a viral infection and resolves within 10 days. Sinus inflammation is defined as inflammation of the mucous membranes that line the walls of the sinuses. Inflammation is divided into several degrees. Acute sinusitis is usually caused by a viral infection.

If the cause is a bacterial infection, they are usually caused by pneumococci or Haemophilus influenzae. While the viral pathogen only lasts 7-10 days, the bacterial infection is more persistent. People with diabetes or HIV are particularly susceptible to this type of infection, but chemical exposure, such as cigarette smoke, also increases susceptibility. A chronic sinus infection lasts longer than three months and can have a variety of different causes, which should be diagnosed individually after the symptoms appear.

Depending on which parts of the paranasal sinuses are affected by the inflammation, symptoms appear in different parts of the facial bones. Typical symptoms are pain , flaccidity and dizziness and/or pressure. Pain and pressure are usually aggravated by changes in body position, such as when the person lies down. Viral infections are cured, and antibiotics can be considered for bacterial infections.

Lisa Newlon
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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.