Anatomy of the nose and paranasal sinuses

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Introduction0:00–0:29

We use our sense of smell for many things, like smelling cookies baking in the oven. But we also use it to help us taste, like when we take a big bite of those cookies.
Our sense of smell is thanks to our nose, but actually our nose does much more than just smell. It also provides a passage for air to reach the lungs and also helps warm and filter that air before it gets down there.
Now, let's go see what the nose knows. Now, the external nose is the part that we see protruding from the midline of our face.

External nose0:29–2:25

Generally speaking, the nose has a pyramidal shaped structure with two openings called the nares or nostrils. These openings are surrounded laterally by the ali, meaning wings, of the nose, and separated from one another medially by the nasal septum.
Inside the nostrils is a nasal vestibule, which is lined by skin and small hairs that help filter dust particles from the air that passes through.
The dorsum of the nose begins at the root, located between the eyebrows and slopes downwards towards the apex, which is the tip of the nose.
OK, so our external nose has a skeleton that helps support its structure, made up of hyaline cartilage and bone. The hyaline cartilage is on the more anterior portion of the nose and provides most of its structure.
In the midline there is the cartilaginous part of the nasal septum or septal cartilage. Two lateral cartilages extend from either side of the dorsal aspect of the septal cartilage.
Anterior inferior to these lateral cartilages are the paired aar cartilages that form the apex and part of the nares of the external nose.
The aar cartilages are thin and flexible, allowing for dilation or constriction of the nares. The bony skeleton gives a base to the nose and includes the nasal part of the frontal bone located at the root of the external nose, two paired nasal bones, the frontal processes of the maxillary bones, and in the midline, there's a superior and posterior inferior bony part of the nasal septum.
The superior part is formed by the perpendicular plate of the ethmoid bone. While the posterior inferior part is formed by a small flat bone known as the vomer with some contribution from the maxillary and palatine bones.

Regions2:25–3:25

Let's take a peek inside the nose now. As we enter the nasal cavity, we first pass through the nares into the nasal vestibule, which is lined by skin.
Moving deeper past the vestibule, the nasal cavity is no longer lined with skin, but with nasal mucosa. The inferior 2/3 of the nasal mucosa is known as the respiratory area, which is lined with respiratory epithelium and is responsible for warming the air we breathe and trapping particles.
The superior third of the nasal mucosa is known as the olfactory area, which is lined with olfactory epithelium and contains the olfactory receptors responsible for the sense of smell.
Going even deeper, the nasal cavity opens to the nasopharynx through posterior nasal apertures called kani. The pharynx is where our air and food passageways meet.
And the nasopharynx is a part of the pharynx located posterior inferior to our nasal cavity. Now, the nasal cavities are similar to duplex houses.

Walls of the nasal cavities3:25–6:03

They're connected in the middle, mirror one another, and have a roof, a floor, and a medial and lateral wall. OK then, let's raise the roof.
The roof of the nose is quite narrow, and it is formed by parts of the ethmoid, frontal, and nasal bones. The major portion of the roof is formed by the cribiform plate of the ethmoid bone, which is a flat horizontal bony plate with small perforations for the fibers of the olfactory nerve to pass through.
The sloping region anterior to the cribiform plate is formed by the frontal and nasal bones and a portion of the septal and aar cartilages posterior to the cribiform plate.
The roof of the nasal cavities is a bit more irregular and is formed by parts of the sphenoid bone, a portion of the vomer bone, and the sphenoidal process of the palatine bone.
Now the floor of the nasal cavity is wider than the roof and consists of the hard palate formed by the horizontal plates of the palatine bone posteriorly and the palatine processes of the maxillary bones anteriorly.
The medial wall is quite simple and consists of both the bony and cartilaginous aspects of the nasal septum. On the other hand, the lateral wall is quite irregular and consists of six bones.
The ethmoid bone forms the majority of the upper part of the lateral wall. Below it are the bones that make up most of the flat surface of the lateral wall from anterior to posterior.
These are the frontal process of the maxilla. The lacrimal bone, the inferior concha, the perpendicular plate of the palatine bone, and the medial pterygoid plate of the sphenoid bone.
The main features that extend from the lateral wall are 3 bony structures known as the nasal concha, which create a greater surface area to warm the air.
The superior and middle nasal concha are extensions of the ethmoid bone, while the inferior concha are individual bones.
These concha divide each nasal cavity into four lateral air passages the sphenoethmoidal recess located above and posterior to the superior concha, and the superior, middle, and inferior meatus located below their respective concha.
These 4 lateral passages open medially into a 5th air passage called the common nasal meatus. Alright, we're a little nosy and want to know how much you can remember.

Quiz6:03–6:25

So here's a little test. Feel free to pause the video and label the missing parts of the lateral and medial wall from A to F.
Awesome. Now before we discuss the sinuses that surround the nose, let's take a look at where they drain in the nose by slicing through the three concha.

Sinuses drainage6:25–7:38

Within the spheno ethmoidal recess, a small opening is located, and this is where the sphenoidal sinus drains. In the superior meatus, the openings of the posterior ethmoidal air cells, or ethmoid sinus can be found.
Now, the middle meatus is slightly different from the others. The frontonasal duct, which drains the frontal sinus, opens into the ethmoidal infundiulum.
The anterior ethmoidal air cells also drain into the ethmoidal infundiulum. Now, continuing from the ethmoidal infundibulu is a groove in the shape of a half moon known as a semi-lunar hiatus.
Draining into the center of the semiunar hiatus is the maxillary sinus. Superior to the semiunar hiatus is the ethmoidal bulla, which is a bulge that contains the openings of the middle ethmoidal cells.
Finally, within the inferior meatus is the opening of the nasollacrimal duct that drains the lacrimal fluid or tears from the lacrimal sac, which is why your nose runs when you cry.
Now that we know where they drain in the nasal cavity, let's explore these sinuses, also known as the paranasal sinuses.

Paranasal sinuses7:38–9:07

The perinatal sinuses are lined with respiratory mucosa and are named after the bones they're located in, which are the frontal, maxillary, ethmoid and sphenoid.
There are two triangular shaped frontal sinuses which are located posterior to the root of the nose. Next is the pair of maxillary sinuses, which are the largest and fill the body of the maxillary bone.
They're shaped like tilted pyramids, with their base located at the inferior part of the lateral wall of the nasal cavity and the apex projecting towards the zygomatic bone.
The floor of the maxillary sinus is superior to the oral cavity. And finally, the roof of the maxillary sinus shares the same bony structure that forms the floor of the orbit.
The ethmoid sinuses, sometimes referred to as ethmoidal air cells, are smaller and are further divided into anterior, middle and posterior ethmoidal sinuses.
All of them are carved inside the ethmoidal labyrinth between the nasal cavities and the orbit. Lastly, the two sphenoidal sinuses are located inside the body of the sphenoid.
The shape of these sinuses is quite variable, but you can think of them like two cubes separated by a septum. Test time.

Quiz9:07–9:21

Let's see if you can identify the perinatal sinuses labeled from A to D here. All righty, now let's move on to the vasculature of the nose.

Vascular supply9:21–11:51

The medial and lateral walls of the nasal cavity are supplied by 5 arteries, which are all branches from the internal and external carotid arteries.
Now, we're going to explore the arterial supply of the nasal cavity like an open book, since a few arteries supply both walls.
These are the senopalatine artery and the anterior and posterior ethmoidal arteries. The senopalatine artery is a branch from the maxillary artery, which is in turn a branch from the external carotid artery.
Now, the senopalatine artery directly enters the nasal cavity through the senopalatine foramen. Here it further divides into a medial and a lateral branch to supply both the lateral wall and the septum.
Next are the anterior and posterior ethmoidal arteries, which originate in the orbit from the ophthalmic artery, a branch from the internal carotid artery.
The anterior and posterior ehemoidal arteries enter the nasal cavity through the cribriform plate, where they branch medially and laterally to supply both walls.
The anterior ethmoidal artery also gives off a small branch to supply the dorsum of the external nose. Now these 3 arteries are all that supply the lateral wall, but the septum has 2 more arteries that supply it, the greater palatine artery and the septal branch of the superior labial artery.
The greater palatine artery first enters the oral cavity posteriorly and runs along the inferior surface of the hard palate.
Then it passes through the incisive canal anteriorly and enters the navel cavity to supply the septum. The superior labial artery is a branch from the facial artery, which is another branch from the external carotid artery.
This artery first surrounds the lip, then gives off the septal branch to supply the septum. Now all 5 arteries supply the septum anastomose anteriorly, forming a vascular network called Kesselbach area.
And this is actually where most nosebleeds originate from. The arterial blood supply of the external nose is supplied by the external nasal branches from the anterior ethmoidal arteries, septal branches from the superior labial arteries.
Nasal branches from the infraorbital arteries and lateral nasal branches from the facial arteries. Now deep to the mucosa that covers the wall of the nasal cavities, there's a submucosal plexus of veins that has two important functions.

Venous drainage11:51–13:39

It helps warm the air that will go into our lungs, and it provides a way to drain the blood supplying the nose. This plexus is formed by veins that follow the same paths of the arteries and drains into the senopalatine, facial, and ophthalmic veins.
The veins that follow the branches of the maxillary artery drain into the senna palatine vein. Which drains into the terragoid plexus of veins found in the teragopalatine fossa.
The superior labial vein follows the same path as the branches of the facial arteries and drains into the facial vein. Finally, the anterior and posterior ethmoidal veins follow the branches of the ophthalmic artery and drain into the ophthalmic vein, which then drains into the cavernous sinus.
The vascular supply of the external nose drains into the dorsal and lateral nasal veins, which join with the angular vein to eventually become the facial vein, which drains into the internal jugular vein.
The facial vein anastomoses anteriorly via the deep facial vein with the pterygoid plexus. This plexus also anastomoses superiorly with the cavernar sinus in the cranial cavity via emissary veins.
Because of these anastomoses, we have an area of the face known as the danger area, which lies within a triangle extending from the root of the nose to the corners of the mouth.
It's called this because an infection entering the facial vein may potentially spread into the cranial cavity via the cavernous sinus.
Last but not least, let's look at the innervation of the nose. Now the nose is best known to convey special sensory information that allows us to smell via the olfactory nerve or cranial nerve one.

Innervation13:39–17:29

This nerve is actually made of several small nerve fascicle, which arise from cells in the olfactory epithelium in the roof of the nasal cavity.
These nerve fascicle bundle together and exit the nasal cavity through small perforations in the cribiform plate of the ethmoid bone in order to synapse in the olfactory bulb inside the cranial cavity.
This information is sent back to the brain along the olfactory tract. The epithelium covering the nasal cavity also conveys general sensory innervation, such as touch or pain.
This information is carried by branches of the trigeminal nerve or cranial nerve 5. Which are the ophthalmic nerve or cranial nerve V1.
And the maxillary nerve or cranial nerve V2. These branches innervate the respiratory region and vestibule of the nasal cavity as well as the perinatal sinuses and parts of the external nose.
The ophthalmic nerve gives off a branch called the nasociliary nerve, which further branches into the anterior and posterior ethmoidal nerves.
The anterior ethmoidal nerve follows the pathways of the anterior ethmoidal artery to innervate the anterior superior part of the medial and lateral walls of the nasal cavity.
It terminates as the external nasal nerve, which supplies the skin around the nares, the nasal vestibule, and the apex of the external nose.
The posterior ethmoidal nerve mostly innervates the ethmoidal cells and the sphenoidal sinus. The nasociliary nerve also gives off the infratrochlear nerve, which innervates the root and dorsum of the external nose.
On the other hand, the maxillary nerve branches into the nasopalatine nerve, which enters the nasal cavity through the sphenopalatine foramen and runs medially to innervate the nasal septum.
The maxillary nerve also supplies the posterior inferior part of the lateral wall via two main branches. First is the greater palatine nerve, which has branches that enter through small foramina within the lateral wall to supply its overlying mucosa.
The maxillary nerve also gives off the posterior superior lateral nasal branch, which also enters through the senopalatine foramen and helps innervate a small part of the lateral wall.
Finally, the maxillary nerve gives rise to the infraorbital nerve that innervates the lateral part of the external nose and the la.
Now, the perinatal sinuses also receive innervation. The frontal sinuses are innervated by the ophthalmic nerve through branches of the supraorbital nerve.
The maxillary sinuses receive innervation from the maxillary nerve through its infraorbital and superior alveolar branches.
The ethmoidal sinuses are innervated by the ophthalmic nerve through the anterior and posterior ethmoidal nerves, which are branches of the nasociliary nerve as well as the maxillary nerve through orbital branches from the terigopalatine ganglion.
And finally, the sphenoidal sinuses are innervated by a posterior ethmoidal branch from the ophthalmic nerve, as well as orbital branches from the terigopalatine ganglion.

Review17:29–20:16

All right, as a quick recap, the nose is made up of the frontal, nasal, and maxillary bones. As well as the septal, lateral, and aar cartilages.
The nasal cavities are separated from one another by the nasal septum, which consists of the septal cartilage anteriorly.
And the ethmoid bone and vomer posteriorly. Each nasal cavity is divided into the respiratory area responsible for the passage, warming and filtering of air, and the olfactory area responsible for the sense of smell.
The roof of the nasal cavity separates it from the cranial cavity, and it's made up of several bones, including the nasal, frontal, ethmoid and sphenoid bones.
The floor separates the nasal cavities from the oral cavity and consists of the hard palate. The medial wall consists of the nasal septum, and finally, the lateral wall has three bony structures called the nasal concha, which divide the nasal cavities into the inferior, middle, and superior meatus and the spheno ethmoidal recess.
The meatuses communicate with the perinatal sinuses, which are four paired spaces filled with air that surround the nasal cavities.
The perinatal sinuses are named after the bones they're located in, and they are the frontal, maxillary, ethmoid, and sphenoidal sinuses.
The frontal, maxillary and anterior ethmoid sinuses drain into the middle nasal meatus, while the posterior ethmoid sinuses drain into the superior nasal meatus, and the sphenoid sinuses drain into the spheno ethmoidal recess.
The middle ethmoid sinuses drain into openings within the ethmoidal bulla. Now the vascularization of the nasal cavities is supplied by 5 arteries, 3 of which supply both the medial and lateral walls.
The senopalatine artery and the anterior and posterior ethmoidal arteries all have medial and lateral branches to supply the septum and the lateral wall.
The septum also receives arterial blood from the greater palatine artery. And the septal branch from the superior labial artery, a branch from the facial artery.
The venous drainage of the nasal cavities drains into a submucosal venous plexus that drains into either the senopalatine, facial, or ophthalmic veins.
Special sensory information for smell is carried by the olfactory nerve or cranial nerve one. While general sensory innervation of the nose is carried by the ophthalmic and maxillary nerves, which are branches of the trigeminal nerve or cranial nerve 5.