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Paranasal Sinuses and Sinusitis

Several open, air-filled chambers called paranasal sinuses (see the image below) are present in the bones surrounding the nasal cavity.Paranasal Sinuses and Sinusitis

Two image descriptionfrontal sinuses are in the bones just above the orbits, and several small image descriptionethmoid air cells (or sinuses) are in the bones between the orbits. Two large image descriptionmaxillary sinuses are in the cheek bones, and and two image descriptionsphenoid sinuses  are in the bones at the base of the skull.

A coronal and sagittal view of the paranasal sinuses
The frontal sinuses highlighted and labeled on coronal and sagittal view of the paranasal sinuses
The ethmoid air cells highlighted and labeled on coronal and sagittal view of the paranasal sinuses
The maxillary sinuses highlighted and labeled on coronal and sagittal view of the paranasal sinuses
The sphenoid sinuses highlighted and labeled on coronal and sagittal view of the paranasal sinuses
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A thin layer of image descriptionrespiratory mucosa(or nasal mucosa) lines the paranasal sinuses. Mucus produced in the sinuses normally drains out of small apertures (or ostia) and adds to the mucus in the nasal cavity.

A coronal and sagittal view of the paranasal sinuses
The respiratory mucosa highlighted and labeled on coronal and sagittal view of the paranasal sinuses
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The open sinuses also help lighten the skull and resonate the voice sounds.

Sinusitis most often occurs when infections, allergies, or tissue irritants cause the sinus mucosa to become inflamed. The edematous (= swollen) membranes block the ostia drainageways that lead to the nasal cavity and mucus accumulates in the open sinus chamber.

Air trapped in the sinus is absorbed into the bloodstream, creating a negative pressure or vacuum. As the vacuum builds, so does the sense of pain. The vacuum may draw fluids into the sinus from the bloodstream. Bacteria and other microbes often grow in these fluids leading to more edema and inflammation.

An Overview of the Paranasal Sinuses and Sinusitis:

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Test yourself while observing the Paranasal Sinuses and Sinusitis anatomy
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