The Different Sinuses and their Anatomy
Quite often, the term ‘sinuses’ is used in relation to certain medical conditions. However, there aren’t too many people who know the role of the sinuses or how they’re made up. Today, our goal is to answer both of these questions so you’re aware the next time the term is used in conversation!
Commonly shortened to ‘the sinuses’, the paranasal sinuses are small cavities filled with air inside the bones of the face; the bones of note are also found in the eyes and nasal cavity. With each sinus, it has a name that represents the bone in which it can be found.
- Frontal: With one per side, the frontal sinuses can be located in the forehead right above the nasal bridge and eyes.
- Maxillary: Found on each side, the maxillary sinus is inside the bone in the cheek.
- Ethmoid: With the ethmoid sinuses, they sit just under the corner of each eye where the bone lies. In many medical diagrams, they’ll show the ethmoid sinus as one sinus but it’s actually made up of several smaller sinuses in a honeycomb shape; it can only be seen properly in CT scan images of the face.
- Sphenoid: Again, the sphenoid sinus is located on both sides but this time behind the ethmoid sinuses. When looking head-on, they won’t be visible so a side view is required instead.
Physiology of the Sinuses
For each sinus, pink membrane will line the outside and it’s responsible for producing mucus to flush the sinus cavities. With a plate of bone and cartilage commonly known as the nasal septum, the two nasal passages are separated. However, the biology of each passage is the same starting with three small ridges of tissue which can be called a concha or turbinate. Depending on whether it’s referring to the upper, middle, or lower structure, they’re designated as superior, middle, or inferior.
When it comes to the draining, the majority of sinuses use the middle turbinate and the drainage occurs below this point. From here, it goes into the osteomeatal complex. For the system to work correctly, air needs to flow uninterrupted through both sides of the nasal passage since this allows for streaming between the nasal septum and turbinates (via the crevices).
For both the mucus and the airflow that started the process, they should end up in the nasopharynx which is a connecting part of the throat towards the back of the nose. As air continues its journey through the windpipes and into the lungs, the mucus takes a different journey and is swallowed instead.
Structures within the Nasal and Sinus Tract
As you probably know, the human body is quite simply amazing and evolution has allowed it to survive on a day-to-day basis using complex scientific principles. Therefore, it probably won’t surprise you to hear that there are some fascinating structures inside the nasal and sinus tract. Below, we have three very important examples:
- Adenoids: As a collection of tissue much like the tonsils, the adenoids are found behind the farthest nasal cavity accessible at the very top of the nasopharynx. While most body parts and important features of the body grow as we get older, this tissue actually starts larger and then disappears during puberty. However, discrepancies in this process can leave it in tact which has the potential to require surgery.
- Tear Duct: Often called the nasolacrimal duct, this is important for our eyes since, without it, tears would continue to build on the inside corners. When it’s in place and functioning as expected, the tears drain into the nasal cavity and this prevents excess moisture within the eyes.
- Eustachian Tube: As our last example, the eustachian tube is required for removing any build-ups that occur within the ears; with the system all interconnected, the opening is found towards the back of the nasopharynx sidewall.
The Role of the Sinuses
Ultimately, the sinuses have many responsibilities within the ear, nose, throat, and beyond but their main role is to produce mucus. When the system is working as it should, the mucus creates a lining on the inside of the nose and this keeps it free from bacteria, fungi, and viruses. If you were to experience dry sinuses, the lack of mucus would leave the nose vulnerable to these pollutants and this leads to irritation and illness.
Over time, cilia, which are tiny hair cells, gradually move the mucus backwards towards the throat where it’s swallowed. Therefore, the steady supply of mucus always takes the same journey while protecting your nose and remaining clean at all times.
After this main function, we should also note that the sinuses are also important for our voices and to lighten the skull. With everything having a purpose, we’re able to enjoy life without consciously worrying about replacing the mucus or producing the right amounts at the right times. As we learn more about the sinuses and how they work, we get an insight into just how fascinating the human body can be!