Paranasal sinuses (sinus paranasales) are paired cavities in the bones of the skull that are formed during fetal development, when part of the bone tissue is replaced with the nasal mucosa. They remain connected to the nasal cavity after birth.

The specific feature of the sinuses is that their mucous membrane is very firmly fused with the periosteum.

There are the following large sinuses:

Maxillary sinus (sinus maxillaris), which is located in the body of the maxilla and is pyramid-shaped.

This sinus has the following walls:

1. Medial wall of the sinus, which is also the lateral wall of the nasal cavity. This sinus communicates with the nasal cavity by the maxillary hiatus (hiatus maxillaris)

There is also a place in the area of the middle nasal meatus where there wall becomes thinner.

2. Anterolateral wall, which has no openings. However, in its middle section, there is the canine fossa (fossa canina), which is the thinnest spot. It is used in surgery to open the sinus cavity.

The anterolateral and medial walls in the junction area form the so-called promontory, which is a bony protrusion.

3. Posterolateral wall, which adheres to the cells of the ethmoidal labyrinth and the sphenoidal sinus.

4. Superior wall, which is the thinnest wall of the sinus. It is also the inferior wall of the orbit. This area is very important from the anatomical point of view, since the infra-orbital neurovascular bundle passes here.

5. Inferior wall, which is the alveolar process of the maxilla. Sometimes the roots of teeth may protrude into the lumen of the sinus. This increases the risk of inflammation in the sinus.

Frontal sinus (sinus frontalis) is a paired pyramid-shaped sinus, which is located in the squamous part of the frontal bone.

It has the following walls:

1. Anterior wall, which is the thickest and is formed by the facial surface of the frontal bone.
2. Posterior (cephalic) wall, which is quite thin, but strong, bordering on the anterior cranial fossa.
3. Inferior wall, which is also the superior wall of the orbit. It partially borders with the cells of the ethmoidal labyrinth and the nasal cavity. On the inferior wall, there is a canal of the frontal sinus through which its cavity communicates with the nasal cavity.
4. Medial wall, which passes between the two frontal sinuses, serving as a bony septum.

Sphenoid sinus (sinus sphenoidalis) is a paired sinus located in the sphenoid bone.

1. Superior wall of the sphenoidal sinus is the inferior surface of the sella turcica. The pituitary gland adheres to this wall.
2. Inferior wall consists of the wall of the nasal cavity and the fornix of the nasopharynx.
3. Posterior wall is formed by a part of the occipital bone
4. Lateral wall is quite thin, it is part of the sphenoid bone and borders on the cavernous venous sinus and the internal carotid artery. There are also a number of nerves, including the oculomotor nerve, the branch of the trigeminal nerve, the trochlear and abducent nerves.

Sinuses of the ethmoid bone or the ethmoid labyrinth (labyrinthus ethmoidalis).

The sinuses of the ethmoid bone (sinus ethmoidalis) are actually cells inside this bone. There are up to 10 on each side. They are formed by thin bone laminae and have different shapes and sizes. Based on their location, there are three groups of these sinuses: anterior and middle sinuses, which communicate with the middle nasal meatus (meatus nasi medius);

and posterior sinuses, which communicate with the superior nasal meatus (meatus nasi superior).

Blood supply

The sinuses are supplied with blood by the maxillary and ophthalmic arteries (a. maxillaris et ophtalmica), and also partially by the branches of the sphenopalatine artery (rr. sphenopalatinae) and the branches of the meningeal arteries (rami arteriae meningeae).

Venous drainage

Venous blood drains into the orbital veins and the veins of the cranial cavity.

Lymphatic drainage

Lymph from the sinuses drains into the lymphatic vessels of the nasal cavity and from there passes to the submandibular and deep cervical lymph nodes.

Innervation

The branches of the trigeminal nerve and the pterygopalatine ganglion innervate the sinuses.

Dictionary

Anatomy of paranasal sinuses

Paranasal sinuses

sinus paranasales

Maxillary sinus

sinus maxillaris

Maxillary ostium

ostium maxillare

Canine fossa

fossa canina

Frontal sinus

sinus frontalis

Sinuses of the ethmoid bone

sinus ossis ethmoidei

Ethmoidal labyrinth

labyrinthus ethmoidalis