Generality
The nose is the prominence located in the center of the face, between the two eyes and the two cheeks, which provides the sense of smell and which represents the main entrance to the respiratory tract.
Externally, the nose has a characteristic pyramid shape, in which it is possible to recognize at least 5 anatomical reference areas: the nasal root, the nasal bridge, the nasal spine, the two nasal wings and the nasal tip.
Internally, the nose corresponds to the two nasal cavities; the latter are two empty spaces deriving from the particular conformation of some bones of the skull (including the ethmoid bone, the vomer, the palatine bones and the maxillary bones).
The flow of oxygenated blood to the nose is mainly due to some branches and sub-branches of the internal carotid arteries and the external carotid arteries.
What is the nose?
The nose is the prominence located in the center of the face, partly between the two eyes and partly between the two cheeks.
Equipped with two openings towards the outside - the so-called nostrils - the nose is the organ of smell and the main entrance to the respiratory tract (the secondary entrance is the mouth).
Anatomy
The nose is a very complex structure, which includes elements of a bone and cartilage nature, blood vessels, lymphatic vessels and nerve endings.
Generally, to simplify the description of the nose, anatomists analyze the external part of the nose separately from the internal part.
Better known as the external nose or nasal pyramid, the external part is the portion of the nose visible to the naked eye, which distinguishes each face and which has a characteristic pyramid shape.
The internal part (or internal nose), on the other hand, is the portion of the nose that coincides with the two nasal cavities and in which the olfactory cells (ie the cells that guarantee the sense of smell) and the structures for the passage of inhaled air reside. , while breathing.
EXTERNAL NOSE
In the external nose, 5 anatomical reference areas can be recognized, which are: the nasal root, the nasal bridge, the nasal spine, the two nasal wings and the nasal tip.
- Nasal root: identifiable where the frontal suture resides, it represents the upper portion of the external nose. It is in continuity with the forehead.
- Nasal bridge: it is the saddle-shaped portion of a horse generally located between the two eyes.
Separate the nasal root from the back of the nose. - Nasal spine: also known as the nasal crest, it is the prominent tract that goes from the nasal bridge to the nasal tip and which distinguishes the shape of the nose.
It is the portion of the nose that stands out to the eyes in profile view. - Nasal wings: are the portions of the external nose lateral to the nasal spine and the nasal tip. They surround the nostrils.
- Nasal tip: also known as the nasal apex, it is the lower portion of the external nose.
In fact, it marks the end of the nasal spine.
Below, it has two distinct openings, better known as the nasal nostrils, which represent the beginning of the two nasal cavities (and of the internal nose).
The skeleton of the external nose includes elements of a bony nature and elements of a cartilage nature.
The elements of a bony nature are: the two nasal bones, the two maxillary bones and the frontal bone.
The elements of cartilage nature, on the other hand, are: the two upper lateral cartilages, the two major alar cartilages (or lower lateral cartilages), the two minor alar cartilages, the septal cartilage and the so-called columella.
- Nasal bones. They form the nasal bridge and the upper part of the nasal spine. Each nasal bone borders: superiorly, with the frontal bone; laterally, with the ipsilateral maxillary bone; finally, medially, with the contralateral nasal bone.
They are cranial bones of the so-called splanchnocranium (see the article on the skull). - Maxillary bones. They support the lateral part of the nose and articulate with numerous bones of the inner nose. Belonging to the splanchnocranium, they are the bones of the jaw.
- Frontal bone. It constitutes a large part of the nasal root. It borders, inferiorly, with the two nasal bones. Belonging to the neurocranium, it is the unequal cranial bone of the forehead.
Figure: the bones of the skull. Thanks to the image, readers can identify the location of some of the cranial bones that participate in the formation of the nose (eg nasal bones, vomer, maxillary bones, ethmoid bone, etc.).
Figure: the cartilages of the external nose.
Among all, the columella is particularly noteworthy. The latter resides in the lower part of the nasal tip and is the strip of cartilage tissue, which separates the right nostril from the left nostril.
The skin lining of the external nose is peculiar. In fact, while the skin covering the bones is thin and devoid of any type of gland, the skin covering the various cartilage structures is thick and rich in sebaceous glands.
The skin lining of the external nose extends to the outer edges of the nasal nostrils; after that, the mucous membrane begins.
INTERNAL NOSE
In the two nasal cavities of the internal nose, experts recognize three anatomical reference regions, which are: the vestibule, the olfactory region and the respiratory region.
- Vestibule: considering the nostrils as the beginning of the internal nose, it is the very first part of the nasal cavity. It is an enlarged area, provided with a characteristic mucous lining.
In adults, it is also the region of the inner nose from which nasal hair can originate. - Olfactory region: located at the apex of the nasal cavity, it is the region of the internal nose in which the olfactory cells reside, ie the cells that guarantee the perception of odors.
- Respiratory region: it is the largest region of the internal nose. It is lined with a ciliated pseudostratified epithelium, in which goblet cells also reside. Goblet cells are cellular elements that secrete mucus.
Various bones of the skull and osteo-cartilaginous components contribute to the particular structure of the internal nose (and of the two nasal cavities). Among the bones, we note: the palatine bones, the ethmoid bone, the inferior turbinates, the vomer and the aforementioned maxillary bones; among the osteo-cartilaginous components, on the other hand, the nasal septum deserves a particular mention, ie the lamina that , interposed between the two nasal cavities, separates them hermetically.
- Palatine bones: they are the two bony elements that form the latero-inferior margin of the nasal cavities, the floors of the orbital cavities and the roof of a part of the hard palate. L-shaped, they articulate each other and with different bones of the skull, including: the ethmoid bone, the maxillary bones, the inferior turbinates and the vomer.
- Ethmoid bone: it is an unequal bone important for the anatomy of the internal nose, as it gives rise, in each nasal cavity, to three very particular structures, called lamina cribrosa, superior turbinate and middle turbinate.
The lamina cribrosa is a kind of plate with small holes, through which the nerve fibers of the olfactory nerve pass.
The superior and middle turbinates, on the other hand, are in fact small bony protrusions, covered by erectile-cavernous vascular tissue (more internally) and by ciliated respiratory mucosa (more externally). As can be guessed, the superior turbinate is so called because it overhangs the middle turbinate. - Lower turbinates: located one in the right nasal cavity and one in the left nasal cavity, are two protrusions similar to the turbinates of the ethmoid bone. The similarity with the latter also concerns the coverings with which they are provided.
Position-wise, the inferior turbinates reside below the superior turbinates and middle turbinates. - Vomere: it is the unequal bone that constitutes the lower part of the nasal septum. Similar to the vomer used by farmers, the vomer of the skull articulates with the palatine and maxillary bones, inferiorly, and the ethmoid bone, anteriorly.
Inside the nasal cavities, the so-called paranasal sinuses are vented through orifices called ostia. The paranasal sinuses are natural cavities filled with air, which are located in the thickness of the facial bones placed around the eyes, nose and cheeks (ethmoid bone, sphenoid bone, frontal bone and maxillary bones). The paranasal sinuses are, in all, 4 pairs: the two frontal sinuses, the two ethmoid sinuses, the two sphenoid sinuses and the two maxillary sinuses.
Their functions are varied: they are essential for the functionality and protection of the respiratory system, increase the perception of odors, lighten the skull, regulate the tone of the voice and promote the drainage of tears and any mucous secretions in the direction of the cavities. nasal.
Posteriorly, the nasal cavities communicate with the mouth, through two openings that take the name of choane.
Most often, anatomy books describe nasal cavities as those empty spaces that run from the vestibule to the nasopharynx.
Also known as nasopharynx, the nasopharynx is the upper part of the pharynx, placed in direct contact with the choanas, the two posterior openings of the nasal cavities.
Figure: nasal cavities. The image shows the anatomical reference regions of the internal nose (they are indicated in different colors), the turbinates, the nasopharynx and some of the paranasal sinuses.
MUSCLES
The nose includes several muscles, which have the task of controlling its movements.
Innervated by the facial nerve (VII cranial nerve), these muscles are: the procerus muscle, the levator muscle of the upper lip and the wing of the nose, the nasal muscle, the depressor muscle of the nasal septum, the anterior dilator muscle of the nostrils and the posterior dilator muscle of the nostrils.
- Procerus muscle: it resides over the nasal bones and over a part of the upper lateral cartilages. Its contraction determines the frowning of the eyebrows and the formation of wrinkles at the level of the nasal bridge.
- Levator upper lip and wing of the nose: equal muscular element, takes place laterally to the ipsilateral nasal nostril and above the ipsilateral maxillary bone. It helps to dilate the nasal nostril, to raise the upper lip and to elevate the nasal wing.
- Nasal muscle: it is an even muscle element, which resides in a lateral position, approximately halfway up the nose. It consists of two parts, which are called the transverse part and the wing part.
The transverse part of the nasal muscle constricts (ie closes) the nasal nostrils; the wing part, on the other hand, dilates the nasal wings. - Nasal septal depressor muscle: it is an even muscular element, which arises at the level of the incisive fossa of the maxillary bone and ends its path at the level of the nasal septum.
From a functional point of view, it assists the wing part of the nasal muscle in its action of dilating the nasal wings. - Anterior dilator muscle of the nostrils and posterior dilator muscle of the nostrils: they are two equal muscular elements, which reside on the sides of the nose, approximately in correspondence with where there are the major and minor alar cartilages.
Com "is easily understood from their name, the anterior dilator muscle of the nostrils and the posterior dilator muscle of the nostrils serve to dilate the nasal nostrils.
VASCULARIZATION OF THE EXTERNAL NOSE
The branches of the maxillary artery and the ophthalmic artery and, secondarily, the angular artery and the lateral nasal artery supply oxygenated blood to the skin of the external nose. The maxillary artery arises from the external carotid artery; the ophthalmic artery from the internal carotid artery; finally, the angular artery and the lateral nasal artery from the facial artery.
The drainage of venous blood belongs to a series of vessels that end in the so-called facial vein, which, in turn, flows into the internal jugular vein.
As for the lymphatic drainage of the external nose, this is due to a network of superficial lymphatic vessels that accompany the facial vein very closely. Like all lymphatic vessels of the head and neck, the lymphatic vessels of the external nose drain their contents into the deep cervical lymph nodes.
VASCULARIZATION OF THE INTERNAL NOSE
Thanks to a "large network of arterial blood vessels," the flow of blood to the internal nose is noticeable. This high blood supply is essential for the heating action of the inhaled air with breathing.
To supply the internal nose with oxygenated blood are:
- The anterior ethmoid artery and the posterior ethmoid artery. These are two branches of the ophthalmic artery, which is, in turn, a branch of the internal carotid artery.
- The sphenopalatine artery, the major palatine artery, the superior labial artery and the lateral nasal arteries. All of these arteries arise directly from the external carotid artery.
In essence, therefore, the blood supply of the internal nose is the responsibility of branches or sub-branches of the internal carotid arteries and of the external carotid arteries.
As regards the drainage of venous blood, this important action affects veins that follow the same path as the aforementioned arteries and that pour their contents into the pterygoid plexus, facial vein, cavernous sinus and sagittal sinus.
INNERVATION OF THE EXTERNAL NOSE
The sensory innervation of the external nose belongs to some sub-branches of the trigeminal nerve, which is the fifth cranial nerve.
Going into more detail:
- The skin sensitivity of the nasal spine and nasal wings belongs to the so-called external nasal nerve. The external nasal nerve is a branch of the ophthalmic nerve, which is, in turn, one of the three main branches of the trigeminal nerve (the other two are the maxillary nerve and the mandibular nerve).
- The skin sensitivity of the lateral portions of the external nose (excluding nasal wings) belongs to the so-called infraorbital nerve, which is a branch of the maxillary nerve.
As already stated, the motor innervation of the external nose (hence the innervation of the muscles of the external nose) is under the control of the facial nerve.
INNERVAZIOENE OF THE INTERNAL NOSE
Experts distinguish the sensory innervation of the internal nose into two different types: the sensory innervation of a special type and the sensory innervation of the general type.
The special sensory innervation (or special sensory innervation) consists of the network of nerve endings, which provide the sense of smell. Specifically, these are the nerve fibers of the olfactory nerves, which go from the olfactory cells of the olfactory region of the inner nose to the olfactory bulb of the brain, passing through the holes in the lamina cribrosa of the ethmoid bone.
Sensory innervation of a general type, on the other hand, consists of the network of nerve endings, which control the internal sensitivity of the nasal cavities, including the vestibule.
- The ophthalmic nerve (main branch of the trigeminal nerve), which innervates the vestibule;
- The nasopalatine nerve and the nasociliary nerve (respectively, branch of the maxillary nerve and branch of the ophthalmic nerve), which innervate the nasal septum and the lateral walls of the nasal cavities.
Development
In the human being, the nose begins to form from the 4th week of gestation: the embryonic portion from which it derives is the so-called neural crest.
Initially, the nose is one with the mouth; then, as the pregnancy progresses, the nose and mouth separate, distinguishing one from the other.
The muscles, cartilages and bones, mentioned above, begin to form and take on their final appearance around the 10th week of intrauterine life. It is at this stage of pregnancy that doctors can identify, through prenatal ultrasound scans. , any nasal malformations.
Function
The olfactory cells, present in the olfactory region of the inner nose, are equipped with specific structures, called olfactory receptors.
The olfactory receptors are the true architects of the sense of smell. In fact, through them the olfactory cells capture odors and stimulate the nerve fibers of the connected olfactory nerves (NB: as you will remember, the olfactory cells are connected to the nerve fibers of the olfactory nerves ).
With the stimulation of the olfactory nerves, the brain - more precisely the olfactory bulbs of the brain - receives information about the smells present in the environment and elaborates, if necessary, the most appropriate responses.
ROLE OF THE NOSE IN THE INTERNAL RESPIRATORY PROCESS
As the first section of the airways, the nose has the task of adapting the inhaled air to the needs of the human body. For this reason, it is equipped with structures (eg: the turbinates or the dense network of blood vessels) that allow it to heat, humidify and purify the air introduced with the respiratory acts.
If the nasal cavities lacked turbinates and their other characteristic structures, the human being would introduce insufficiently hot air into the lungs, not purified from germs and not properly humidified.
Pathologies
The nose can be the victim of: fractures of some of its bony parts, deformations of some of its osteo-cartilage components or other morbid conditions, including for example the hypertrophy of the turbinates.
In addition, the nose can be the site of well-known and common clinical manifestations, such as nosebleeds (or epistaxis), the so-called runny nose (or runny nose) or a stuffy nose.
FRACTURES OF THE NOSE
Fractures of one or more bony components of the nose are almost always injuries of traumatic origin.
The most important types of nose fractures are the fracture of one or both nasal bones and the fracture of the lamina cribrosa.
Fractures of the nasal bones are quite common conditions, which rarely involve complications and require surgery. Typical symptoms consist of: pain, local swelling, bruising on the nose and under the eyes, nosebleed, breathing problems and more or less marked anatomical deformities.
As for the fractures of the lamina cribrosa, these are fortunately unusual conditions, which can have serious repercussions in the brain. In fact, if the traumatic event affecting the lamina cribrosa is considerable, the latter can break in such a way that some bone fragments penetrate into the nearby meningeal layers, breaking them and causing the leakage of cerebrospinal fluid. With the leakage of part of the cerebrospinal fluid and damage to the meninges, the risk of meningitis, encephalitis and / or brain abscess increases.
For a better understanding of nasal bone fractures, readers can consult the article related to the broken nose.
DEFORMATIONS OF THE NOSE
The best known and most common deformation of the structures of the nose is the deviation of the nasal septum.
The deviation of the nasal septum is a condition that can be present from birth or that can appear following a traumatic event.
The only way to correct a nasal septal deviation is through surgery, known as septoplasty.
The recourse to septoplasty is foreseen only when the deviation of the nasal septum involves symptoms and complications, incompatible with a normal life.
For a better understanding of the deviation of the nasal septum, readers can consult the article on the deviated nasal septum.
HYPERTROPHY OF THE TURBINATES
Turbinate hypertrophy is the result of chronic and permanent swelling of the ciliated respiratory mucosa of the turbinates. This swelling leads to a reduction in the space available for normal nasal breathing, so those suffering from turbinate hypertrophy develop symptoms such as:
- Stuffy nose, which causes you to breathe through your mouth;
- Dry mouth
- Decreased sense of smell (hyposmia);
- Nasal itching;
- Tendency to snore and sleep apnea;
- Leakage of serous material from the nose (runny nose).
