Nose Function: Structure, Clinical Significance, Anatomy, Blood Supply and Nasal Innervation

It is the protruding part of the face that bears the nostrils.

The shape of the nose is determined by the nasal bones and nasal cartilages, including the septal cartilage (which separates the nostrils) and the upper and lower lateral cartilages.

On average, a man’s nose is larger than a woman’s.

The nose has an area of ​​specialized cells that are responsible for smell (part of the olfactory system ). Another function of the nose is to condition the inhaled air, heat it, and make it more humid.

Sneezing is usually caused by foreign particles that irritate the nasal mucosa, but more rarely it can be caused by sudden exposure to bright light (called the aesthetic sneeze reflex) or by touching the ear canal.

Sneezing can transmit infections by creating aerosols in which the droplets can harbor germs. As part of the respiratory system, the nose serves several functions.

Nose function

They have many functions, but some that are very relevant are their sensory functions. In fact, these are some of our oldest senses (evolutionarily).

What the nose does in the respiratory system, helps in inhalation

The nostrils are the entrance to the respiratory tract, which means that during inhalation, air enters the body through the nostrils and exits in the same way during exhalation.

Behind the nostrils, the two sides of the nasal cavity (divided by the septum) open into a space called the choana, which then opens into the nasopharynx (the upper part of the pharynx or throat).

The air then reaches the oropharynx, the region behind the mouth, just after the nasopharynx. In this way, the inhaled air travels through the larynx, trachea and bronchi to reach the lungs.

Purifying and modifying the air, why do you have hair on your nose?

Cilia, or hairs that line the inner walls of the nasal cavity, along with the mucous lining, purify the inhaled air by trapping dust, pollen, and other harmful particles, preventing them from entering the internal parts of the body.

Basically the hairs inside the nose prevent large particles from entering the lungs.

Cilia also serve to get rid of these impurities as their backward sweeping motion helps carry harmful particles down the throat where they can be swallowed, or into the nasal cavity to be excreted.

Another purpose of the nose hairs and mucus is to heat and hydrate the air, so that it matches the ideal air temperature and humidity within the lungs (98.6 ° F and 100%).

After oxygen-carbon dioxide exchange within the lungs, CO2-rich air travels through the airways, reaching the nasal cavities where the nasal hair absorbs heat and moisture from the air before it leaves the body through the The nostrils.

The bones of the coiled nasal concha play a vital role here, in keeping the air circling for longer within the nasal cavity so that it can be better purified and humidified.

Function as the organ of smell

The human brain can distinguish between at least 1 trillion different smells, and the nose is the way to get to the odor section of the brain.

When inhaled air comes into contact with the roof of the nasal cavity (olfactory epithelium), the nerve fibers that extend from the olfactory receptors pick up the odorant molecules to send them to the olfactory bulbs through the receptors.

These nerve signals are carried to the olfactory region in the brain to be decoded so that the smell can be identified.

Taste organ assistance

The mouth (among other connected structures, such as the epiglottis, etc.) has taste buds filled with taste receptor cells. These cells transduce chemicals in what we eat to neuronal activity.

The nose contains the olfactory epithelium, which contains olfactory receptor neurons, responsible for the transduction of diffuse airborne chemicals into neuronal signals.

For each, different chemicals activate different populations of cells in different regional distributions at different levels.

Taken together, this sensory and population mapping encodes second-order neurons (namely, taste afferent axons and glomerulus mitral cells, for taste and smell, respectively).

How does your nose help you “taste” things?

The nose also plays a vital role in the way you taste your food. The taste buds on your tongue can only recognize if something is sweet, sour, sour, or salty. So for all other taste and flavor sensations, you rely on your nose’s ability to smell.

Why does your nose runny when you cry?

There are a few other openings in the nasal cavity, apart from the sinuses. The nasolacrimal duct that drains tears from the eyes also opens into the nasal cavity, to the inferior meatus below the inferior shell.

So when you cry, some of the tears produced by your tear ducts drain into your nasal cavity, where they mix with mucus, making your nose runny.

Structure

Your nose is made up of bone and cartilage, separated into two symmetrical nostrils. The open sinus spaces sit on your forehead, at the top of your nostrils.

The nasal root is the top part of the nose, forming an indentation at the suture where the nasal bones meet the frontal bone.

The anterior nasal spine is the thin projection of bone in the midline at the lower nasal margin, supporting the cartilaginous center of the nose. Adult humans have nasal hairs in the anterior nasal passage.

Divisions

Portal : the area just behind the nostrils, this is the part of the nasal cavity most exposed to threats from the environment.

So this part is filled with multiple layers of the same cells that make up our skin (stratified squamous epithelium), forming a protective barrier.

This area also has stiff nose hairs (vibrissae) embedded in the cell lining and covered in thick mucus.

Respiratory region : begins at the end of the vestibular area and includes the entire nasal cavity, in addition to the olfactory region.

This region has a lining of ciliated pseudostratified epithelium (layer of individual cells) that contains goblet cells that secrete mucus that forms the mucous membrane.

Olfactory region : the upper part of the nasal cavity, near the septum, is filled with olfactory cells and olfactory mucosa. The mucosa is home to countless cilia, which contain olfactory receptor proteins that are responsible for the sense of smell.

Clinical significance

One of the most common medical conditions affecting the nose is nosebleeds (in medicine: epistaxis). Most of them occur in the Kiesselbach area (synonym: Little area).

Nasal congestion is a common symptom of infections or other inflammations of the nasal lining (rhinitis), as in allergic rhinitis or vasomotor rhinitis (a result of nasal spray abuse).

Most of these conditions also cause anosmia, which is the medical term for loss of smell. This can also occur in other conditions, for example after trauma, in Kallmann syndrome or in Parkinson’s disease.

The nose is a common site for foreign bodies. The nose is susceptible to frostbite. Nasal flare is a sign of respiratory distress that involves widening of the nasal passages on inspiration.

Due to the special nature of the blood supply to the human nose and surrounding area, it is possible for retrograde infections of the nasal area to spread to the brain.

For this reason, the area from the corners of the mouth to the bridge of the nose, which includes the nose and jaw, is known to physicians as the danger triangle of the face.

Specific systemic diseases, infections, or other conditions that can lead to destruction of part of the nose:

For example, nasal bridge or nasal septum perforation) are rhinophyma, skin cancer (eg, basal cell carcinoma), granulomatosis with polyangiitis, systemic lupus erythematosus, rheumatoid arthritis, tuberculosis, syphilis, leprosy, and cocaine exposure, chromium or toxins.

The nose can be stimulated to grow into acromegaly.

Your nose keeps growing all your life

There is a common myth that the human nose never stops growing, even after reaching adulthood. In truth, the nose doesn’t actually keep growing, but its shape alters a bit as we age.

Since the upper part of the outer nose is supported by bones (nasal bones), there are no noticeable changes in its appearance. However, the cartilage that supports the bottom of the nose weakens with age, causing the tip of the nose to droop, making it appear flatter and wider.

Anatomy of the nose

The external nose

The outer part of the nose has a triangular or pyramidal shape, with the highest point called the apex or tip of the nose.

The thin upper part that blends into the forehead is called the root of the nose, while the region between the apex and the root is called the back. The small curve just below the root is known as the bridge of the nose.

Below the apex are the nostrils or nostrils, surrounded by the nasal septum and the cartilaginous nasal ala or the wings of the nose.

Nasal Cavity

The nasal cavity is the space behind the nostrils and the beginning of the respiratory tract. It is separated into the right and left nasal cavities by the nasal septum. There are three sections of the cavity:

Nasal portal : the area just behind the nasal cavities, the nasal vestibule is covered with skin tissue, unlike the rest of the nasal cavity.

It is surrounded by the wings of the nose and the nasal septum, while its floor is formed by the hard palate.

Respiratory region : the large space within the nose covered with cilia and mucus-secreting goblet cells.

Olfactory region : The highest point of the nasal cavity, the olfactory region contains the olfactory receptor neurons. Humans have around 5 to 6 million of these receptors (as opposed to dogs who have 220 million).

There are two olfactory receptor patches in each nasal cavity, located below the two olfactory bulbs, the region that connects the nose to the olfactory (scent region) of the brain.

Nasal skeleton : what bones and cartilage are in your nose.

The nasal walls are made up of three pairs and two unpaired bones; the pairs are the nasal, palatine, and maxillary bones, while the vomer and ethmoid bones are unpaired.

In addition, there are three pairs of nasal conchae (nasal turbinates) that spiral outward from the sides of the nasal cavity on both sides.

The primary cartilages in the human nose include the lateral, septal, and major and minor alar cartilages.

Bones and cartilage of the external nose

The upper part of the human nose is quite hard and bony, with the nasal bones forming the nasal bridge, while the sides of the upper external nose are supported by the frontal processes and the medial plates of the maxilla.

The flexible lower part is composed of the lateral cartilages, alar major and minor alar along with the cartilaginous septum.

The large lateral and greater alar cartilages (two of each for the two sides of the nose) play a major role in shaping the nose.

The number of lesser alar cartilage often varies from person to person, usually ranging from three to four on each side.

The inner walls of the nose

Nasal septum: the front part of the septum is made up of the septal cartilages, while its posterior end joins the front part of the ethmoid and vomer bones, as well as the perpendicular plate of the ethmoid bone.

The floor : the hard palate, located where the cavities of the nose and mouth meet, and keeping them separated from each other, forms the horizontal floor of the nasal cavity. The specific bones involved are the palatine process of the maxilla and the horizontal plate of the palatine bone.

The roof : The relatively narrow roof is made up of the lower frontal part of the frontal bone, the two nasal bones, the cribriform plate of the ethmoid bone, as well as the sphenoid bone and the wing of the vomer.

Nasal shell

There are three pairs of nasal concha: inferior, middle and superior nasal concha.

The Lower Nasal Shell : The largest of the three turbinates (almost as long as an index finger), the lower turbinates are a pair of identical bones, covered by a thick layer of mucus, located below the upper and middle turbinates.

Unlike the other two bones, the lower shell is considered a bony structure on its own, it sits on the nasal septum, separating the two nasal cavities.

The flat spongy bone has a curled up appearance, resembling parchment. It has a convex medial surface that has multiple longitudinal grooves that allow blood vessels to transport to the mucus layer that covers the bone.

The concave lateral surface of the nasal concha partially forms the limit of the inferior meatus. It can be separated into three different portions:

  • The anterior portion that articulates with the maxilla.
  • The posterior part articulates with the palatine.
  • The middle portion has three well-defined processes.

They vary in size and shape; the pointed or small anterior lacrimal process articulates with the lacrimal bone on its upper side, while its margins articulate with the upper jaw.

This joint helps in the formation of the nasolacrimal canal. The thin, broad ethmoid process behind the lacrimal process joins the ethmoid bone.

Another thin lamina called the maxillary process extends downward to articulate with the maxilla, partially forming the medial wall of the maxillary sinus.

The ossification of the turbinate occurs from the single center that appears in the fifth month of fetal growth in the cartilaginous lateral wall of the developing nasal capsule.

The middle nasal concha : As its name suggests, the middle nasal concha or the middle nasal turbinate is the bone located between the superior and inferior conchae.

Being about the size of the little finger, it has a rough, rough surface, forming the lower border of the medial plate of the lateral mass (labyrinth) of the ethmoid.

The branches of the olfactory nerves lodged in the sulci are distributed to the thick mucous membrane that covers the superior nasal turbinate. The middle meatus is located below the curved edge of the middle shell.

The thin bone protects the maxillary and ethmoid sinuses, preventing any direct contact between them and the pressurized nasal airflow. Most of the air inhaled during each breath travels between the middle meatus and the inferior turbinate.

The Superior Nasal Shell : The small, delicate shell-shaped bone located above the other two turbinates, projecting toward the plate perpendicular from the ethmoid bone, is the superior concha or superior turbinate. It is considered a part of the ethmoid bone.

Located below and lateral to this bone is the superior meatus, a narrow oblique fissure where the posterior ethmoid cells open.

The sphenoethmoidal recess, the narrow opening of the sphenoid sinus, is located directly above the superior shell. The superior meatus and the sphenoethmoidal recess are separated from each other by this shell.

Paranasal sinuses

There are certain air-filled areas within the bones that surround the nasal cavity. These empty spaces, which have a lining of respiratory mucosa on their inner walls, are all centered in the nasal cavity, and are called the paranasal sinuses.

There are four paired paranasal sinuses in humans, named for the bones in which they are found: maxillary, ethmoid, sphenoid, and frontal sinus. All the drainage in the nasal cavity, the sinus openings are located in its side walls and the roof.

Blood supply to the nose

Arterial supply

The nose has a rich blood supply provided by the arterial branches of the internal and external carotid. The former includes the posterior and anterior ethmoid arteries, while the latter includes the sphenopalatine artery, the greater palatal artery, the superior labial artery, and the angular artery.

Vasculature of the external nose

The superior labial artery, a branch of the facial artery, supplies the external region of the nose. The vascular supply to the dorsal and sellar regions (the area in the sphenoid bone that houses the pituitary gland) comes from the maxillary and internal ophthalmic arteries.

Internal vasculature

The sphenopalatine artery, together with the anterior and posterior ethmoid arteries, supply the lateral wall of the nose.

These arteries also cause a blood supply to the nasal septum and side walls, with additional sources of vascular supply including the greater (posterior) palatal artery and the superior (anterior) labial artery.

Kiesselbach’s plexus : This refers to a small area in the lower anterior part of the nasal septum that marks the point of convergence for the three primary blood supplies from the inner nose. This is the area where nosebleeds occur in more than 90% of cases.

Venous supply

The venous system of the nose follows the arteries, draining into the ophthalmic and facial veins, as well as into the pharyngeal and pterygoid plexuses.

Nasal innervation

The supply of nerves to the human nose can be classified into two sections according to their functions:

Special sensory innervation : refers to the sense of smell controlled by the olfactory nerves (CN1).

The olfactory sensory fibers run through the cribriform plate of the ethmoid bone to connect to the olfactory bulb located superior to the nasal cavity.

The neural receptors in this streak come into contact with any particles and chemicals that enter the nose and send them to the olfactory region of the brain to “smell.”

General sensory innervation : refers to the general senses of the external nose and nasal cavity.

The lateral walls of the nasal cavity and septum are innervated by the branch of the maxillary nerve, known as the nasopalatine nerve, and the branch of the ophthalmic nerve called the nasociliary nerve. The trigeminal nerve innervates the outer skin of the human nose.