Human nose

Several bones and cartilages make up the bony-cartilaginous framework of the nose, and the internal structure.The topmost bony part of the nose is formed by the nasal part of the frontal bone, which lies between the brow ridges, A left and a right nasal bone join with the nasal part of the frontal bone at either side; and these at the side with the small lacrimal bones and the frontal process of each maxilla. It is also an important cephalometric landmark. Cartilages The nasal cartilages are the septal, lateral, major alar, and minor alar cartilages. The major and minor cartilages are also known as the greater and lesser alar cartilages. There is a narrow strip of cartilage called the vomeronasal cartilage that lies between the vomer and the septal cartilage. The septal nasal cartilage, extends from the nasal bones in the midline, to the bony part of the septum in the midline, posteriorly. It then passes along the floor of the nasal cavity. The septum is quadrangular–the upper half is attached to the two lateral nasal cartilages, which are fused to the dorsal septum in the midline. The septum is laterally attached, with loose ligaments, to the bony margin of the anterior nasal aperture, while the inferior ends of the lateral cartilages are free (unattached). The three or four minor alar cartilages are adjacent to the lateral cartilages, held in the connective tissue membrane, that connects the lateral cartilages to the frontal process of the maxilla. The nasal bones in the upper part of the nose are joined by the midline internasal suture. They join with the septal cartilage at a junction known as the rhinion. The rhinion is the midline junction where the nasal bone meets the septal cartilage. From the rhinion to the apex, or tip, the framework is of cartilage. The major alar cartilages are thin, U-shaped plates of cartilage on each side of the nose that form the lateral and medial walls of the vestibule, known as the medial and lateral crura. The medial crura are attached to the septal cartilage, forming fleshy parts at the front of the nostrils on each side of the septum, called the medial crural footpods. The medial crura meet at the midline below the end of the septum to form the columella and lobule. The lobule contains the tip of the nose and its base contains the nostrils. The major alar cartilages are freely moveable and can respond to muscles to either open or constrict the nostrils. There is a reinforcing structure known as the nasal scroll that resists internal collapse from airflow pressure generated by normal breathing. This structure is formed by the junction between the lateral and major cartilages. Their edges interlock by one scrolling upwards and one scrolling inwards. Muscles The muscles of the nose are a subgroup of the facial muscles. They are involved in respiration and facial expression. The muscles of the nose include the procerus, nasalis, depressor septi nasi, levator labii superioris alaeque nasi, and the orbicularis oris of the mouth. As are all of the facial muscles, the muscles of the nose are innervated by the facial nerve and its branches. The SMAS is continuous from the nasofrontal process to the nasal tip. It divides at level of the nasal valve into superficial and deep layers, each layer having medial and lateral components. The nasal dorsum also known as the nasal ridge is the border between the root and the tip of the nose, which in profile can be variously shaped. The ala of the nose (ala nasi, "wing of the nose"; plural alae) is the lower lateral surface of the external nose, shaped by the alar cartilage and covered in dense connective tissue. Differences in the symmetry of the nose have been noted in studies. Asymmetry is predominantly seen in wider left-sided nasal and other facial features. Nasal cavity labelled NALT|alt= The nasal cavity is the large internal space of the nose, and is in two parts – the nasal vestibule and the nasal cavity proper. The nasal cavity is divided into two cavities by the nasal septum, and each is accessed by an external nostril. At the back of the nasal cavity there are two openings, called choanae (also posterior nostrils), that give entrance to the nasopharynx, and rest of the respiratory tract. The term concha refers to the actual bone; when covered by soft tissue and mucosa, and functioning, a concha is termed a turbinate. Most of the nasal cavity and paranasal sinuses is lined with respiratory epithelium as nasal mucosa. In the roof of each cavity is an area of specialised olfactory epithelium. This region is about , covering the superior concha, the cribriform plate, and the nasal septum. The nasal cavity has a nasal valve area that includes an external nasal valve, and an internal nasal valve. The external nasal valve is bounded medially by the columella, laterally by the lower lateral nasal cartilage, and posteriorly by the nasal sill. The internal nasal valve is bounded laterally by the caudal border of the upper lateral cartilage, medially by the dorsal nasal septum, and inferiorly by the anterior border of the inferior turbinate. The internal nasal valve is the narrowest region of the nasal cavity and is the primary site of nasal resistance. The valves regulate the airflow and resistance. Air breathed in is forced to pass through the narrow internal nasal valve, and then expands as it moves into the nasal cavity. The sudden change in the speed and pressure of the airflow creates turbulence that allows optimum contact with the respiratory epithelium for the necessary warming, moisturising, and filtering. The turbulence also allows movement of the air to pass over the olfactory epithelium and transfer odour information. Four paired paranasal sinuses – the frontal sinus, the sphenoid sinus, the ethmoid sinus and the maxillary sinus drain into regions of the nasal cavity. The sinuses are air-filled extensions of the nasal cavity into the cranial bones. Adults have a high concentration of cilia in the ostia. The cilia in the sinuses beat towards the openings into the nasal cavity. The increased numbers of cilia and the narrowness of the sinus openings allow for an increased time for moisturising, and warming. Paul Topinard developed the nasal index as a method of classifying ethnic groups. The index is based on the ratio of the breadth of the nose to its height. The nasal dimensions are also used to classify nasal morphology into five types: Hyperleptorrhine is a very long, narrow nose with a nasal index of 40 to 55. Variations in nose size between ethnicities may be attributed to differing evolutionary adaptations to local temperatures and humidity. Other factors such as sexual selection may also account for ethnic differences in nose shape. Some deformities of the nose are named, such as the pug nose and the saddle nose. The pug nose is characterised by excess tissue from the apex that is out of proportion to the rest of the nose. A low and underdeveloped nasal bridge may also be evident. A saddle nose deformity involving the collapse of the bridge of the nose is mostly associated with trauma to the nose but can be caused by other conditions including leprosy. Werner syndrome, a condition associated with premature aging, causes a "bird-like" appearance due to pinching of the nose. Down syndrome commonly presents a small nose with a flattened nasal bridge. This can be due to the absence of one or both nasal bones, shortened nasal bones, or nasal bones that have not fused in the midline. ==Blood supply and drainage==

Supply .|alt= The blood supply to the nose is provided by branches of the ophthalmic, maxillary, and facial arteries – branches of the carotid arteries. Branches of these arteries anastomose to form plexuses in and under the nasal mucosa. This plexus is made up of large thin-walled veins with little soft tissue such as muscle or fiber. The mucosa of the plexus is thin with very few structures. ==Lymphatic drainage==

From different areas of the nose superficial lymphatic vessels run with the veins, and deep lymphatic vessels travel with the arteries. Lymph drains from the anterior half of the nasal cavity, including both the medial and lateral walls, to join that of the external nasal skin to drain into the submandibular lymph nodes. The rest of the nasal cavity and paranasal sinuses all drain to the upper deep cervical lymph nodes, either directly or through the retropharyngeal lymph nodes. The back of the nasal floor probably drains to the parotid lymph nodes. ==Nerve supply==

The nerve supply to the nose and paranasal sinuses comes from two branches of the trigeminal nerve (CN V): the ophthalmic nerve (CN V1), the maxillary nerve (CN V2), and branches from these. The frontal sinus is supplied by branches of the supraorbital nerve. The ethmoid sinuses are supplied by anterior and posterior ethmoid branches of the nasociliary nerve. The sphenoid sinus is supplied by the posterior ethmoidal nerves. Movement The muscles of the nose are supplied by branches of the facial nerve. The nasalis muscle is supplied by the buccal branches. It may also be supplied by one of the zygomatic branches. The procerus is supplied by temporal branches of the facial nerve and lower zygomatic branches; a supply from the buccal branch has also been described. The depressor septi is innervated by the buccal branch, and sometimes by the zygomatic branch, of the facial nerve. The levator labii superioris alaeque nasi is innervated by zygomatic and superior buccal branches of the facial nerve. Smell The sense of smell is transmitted by the olfactory nerves. Olfactory nerves are bundles of very small unmyelinated axons that are derived from olfactory receptor neurons in the olfactory mucosa. The axons are in varying stages of maturity, reflecting the constant turnover of neurons in the olfactory epithelium. A plexiform network is formed in the lamina propria, by the bundles of axons that are surrounded by olfactory ensheathing cells. In as many as twenty branches, the bundled axons cross the cribriform plate and enter the overlying olfactory bulb ending as glomeruli. Each branch is enclosed by an outer dura mater that becomes continuous with the nasal periosteum. Autonomic supply The nasal mucosa in the nasal cavity is also supplied by the autonomic nervous system. Postganglionic nerve fibers from the deep petrosal nerve join with preganglionic nerve fibers from the greater petrosal nerve to form the nerve of the pterygoid canal. Sympathetic postganglionic fibers are distributed to the blood vessels of the nose. Postganglionic parasympathetic fibres derived from the pterygopalatine ganglion provide the secretomotor supply to the nasal mucous glands, and are distributed via branches of the maxillary nerves. ==Development==

at about four weeks. The olfactory pit can be seen at the top. Development of the nose In the early development of the embryo, neural crest cells migrate to form the mesenchymal tissue as ectomesenchyme of the pharyngeal arches. By the end of the fourth week, the first pair of pharyngeal arches form five facial prominences or processes – an unpaired frontonasal process, paired mandibular processes and paired maxillary processes. The nose is largely formed by the fusion of these five facial prominences. The frontonasal process gives rise to the bridge of the nose. The medial nasal processes provide the crest and the tip of the nose, and the lateral nasal processes form the alae or sides of the nose. The frontonasal process is a proliferation of mesenchyme in front of the brain vesicles, or extremely rarely polyrrhinia the formation of a duplicate nose. Normal development is critical because the newborn infant breathes through the nose for the first six weeks, and any nasal blockage will need emergency treatment to clear. Development of the paranasal sinuses The four pairs of paranasal sinuses – the maxillary, ethmoid, sphenoid, and frontal, develop from the nasal cavity as invaginations extending into their named bones. Two pairs of sinuses form during prenatal development and two pairs form after birth. The maxillary sinuses are the first to appear during the fetal third month. They slowly expand within the maxillary bones and continue to expand throughout childhood. The maxillary sinuses form as invaginations from the nasal sac. The ethmoid sinuses appear in the fetal fifth month as invaginations of the middle meatus. The ethmoid sinuses do not grow into the ethmoid bone and do not completely develop until puberty. The sphenoid sinuses are extensions of the ethmoid sinuses into the sphenoid bones. They begin to develop around two years of age, and continue to enlarge during childhood. The frontal sinuses only develop in the fifth or sixth year of childhood, and continue expanding throughout adolescence. Each frontal sinus is made up of two independent spaces that develop from two different sources; one from the expansion of ethmoid sinuses into frontal bone, and the other develops from invagination. They never coalesce so drain independently. ==Function==

Respiration The nose is the first organ of the upper respiratory tract in the respiratory system. Its main respiratory function is the supply and conditioning, by warming, moisturising and filtering of particulates of inhaled air. The three positioned nasal conchae in each cavity provide four grooves as air passages, along which the air is circulated and moved to the nasopharynx. The internal structures and cavities, including the conchae and paranasal sinuses form an integrated system for the conditioning of the air breathed in through the nose. The turbulence created by the conchae and meatuses optimises the warming, moistening, and filtering of the mucosa. A major protective role is thereby provided by these structures of the upper respiratory tract, in the passage of air to the more delicate structures of the lower respiratory tract. Photic sneezing is a reflex brought on by different stimuli such as bright lights. The nose is also able to provide sense information as to the temperature of the air being breathed. Variations in shape of the nose have been hypothesised to possibly be adaptive to regional differences in temperature and humidity, though they may also have been driven by other factors such as sexual selection. Sense of smell ) are shown here The nose also plays the major part in the olfactory system. It contains an area of specialised cells, olfactory receptor neurons responsible for the sense of smell (olfaction). Olfactory mucosa in the upper nasal cavity, contains a type of nasal gland called olfactory glands or Bowman's glands, which help in olfaction. The nasal conchae also help in olfaction function, by directing air-flow to the olfactory region. Speech Speech is produced with pressure from the lungs. This can be modified using airflow through the nose in a process called nasalisation. This involves the lowering of the soft palate to produce nasal vowels and consonants by allowing air to escape from both the nose and the mouth. Nasal airflow is also used to produce a variety of click consonants called nasal clicks. The large, hollow cavities of the paranasal sinuses act as resonating chambers that modify, and amplify speech and other vocal vibrations passing through them. ==Clinical significance==

One of the most common medical conditions involving the nose is a nosebleed (epistaxis). Most nosebleeds occur in Kiesselbach's plexus, a vascular plexus in the lower front part of the septum involving the convergence of four arteries. A smaller proportion of nosebleeds that tend to be nontraumatic occur in Woodruff's plexus. Woodruff's plexus is a venous plexus of large thin-walled veins lying in the posterior part of the inferior meatus. One of the causes of snoring is nasal obstruction, and anti-snoring devices such as a nasal strip help to flare the nostrils and keep the airway open. Most conditions of nasal congestion also cause a loss of the sense of smell (anosmia). This may also occur in other conditions, for example following trauma, in Kallmann syndrome or Parkinson's disease. A blocked sinus ostium, an opening from a paranasal sinus, will cause fluid to accumulate in the sinus. In children, the nose is a common site of foreign bodies. The nose is one of the exposed areas that is susceptible to frostbite. Because of the special nature of the blood supply to the human nose and surrounding area, it is possible for retrograde infections from 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, including the nose and maxilla, is known as the danger triangle of the face. skin cancers particularly basal-cell carcinoma, paranasal sinus and nasal cavity cancer, granulomatosis with polyangiitis, leprosy, chromium and other toxins. The nose may be stimulated to grow in acromegaly, a condition caused by an excess of growth hormone. A common anatomic variant is an air-filled cavity within a concha known as a concha bullosa. In rare cases a polyp can form inside a bullosa. Usually a concha bullosa is small and without symptoms but when large can cause obstruction to sinus drainage. Some drugs can be nasally administered, including drug delivery to the brain, and these include nasal sprays and topical treatments. The septal cartilage can be destroyed through the repeated inhalation of recreational drugs such as cocaine. This, in turn, can lead to more widespread collapse of the nasal skeleton. Sneezing can transmit infections carried in the expelled droplets. This route is called either airborne transmission or aerosol transmission. Surgical procedures from 17th century Europe. Badly positioned alar cartilages lack proper support, and can affect the function of the external nasal valve. This can cause breathing problems particularly during deep inhalation. The surgical procedure to correct breathing problems due to disorders in the nasal structures is called a rhinoplasty, and this is also the procedure used for a cosmetic surgery when it is commonly called a "nose job". For surgical procedures of rhinoplasty, the nose is mapped out into a number of subunits and segments. This uses nine aesthetic nasal subunits and six aesthetic nasal segments. A septoplasty is the specific surgery to correct a nasal septum deviation. A broken nose can result from trauma. Minor fractures may heal on their own. Surgery known as reduction may be carried out on more severe breaks that cause dislocation. Several nasal procedures of the nose and paranasal sinuses can be carried out using minimally-invasive nasal endoscopy. These procedures aim to restore sinus ventilation, mucociliary clearance, and maintain the health of the sinus mucosa. Some non-nasal surgeries can also be carried out through the use of an endoscope that is entered through the nose. These endoscopic endonasal surgeries are used to remove tumours from the front of the base of the skull. Swollen conchae can cause obstruction and nasal congestion, and may be treated surgically by a turbinectomy. ==Society and culture==

Some people choose to have cosmetic surgery (called a rhinoplasty) to change the appearance of their nose. Nose piercings, such as in the nostril, septum, or bridge, are also common. In certain Asian countries such as China, Japan, South Korea, Malaysia, Thailand and Bangladesh, rhinoplasties are commonly carried out to create a more developed nose bridge or a "high nose". Similarly, "DIY nose lifts" in the form of re-usable cosmetic items have become popular and are sold in many Asian countries such as China, Japan, South Korea, Taiwan, Sri Lanka and Thailand. A high-bridged nose has been a common beauty ideal in many Asian cultures dating back to the beauty ideals of ancient China and India. In New Zealand, nose pressing ("hongi") is a traditional greeting originating among the Māori people. However it is now generally confined to certain traditional celebrations. The Hanazuka monument enshrines the mutilated noses of at least 38,000 Koreans killed during the Japanese invasions of Korea from 1592 to 1598. Nose picking is a common, mildly taboo habit. Medical risks include the spread of infections, nosebleeds and, rarely, perforation of the nasal septum. When it becomes compulsive it is termed rhinotillexomania. The wiping of the nose with the hand, commonly referred to as the "allergic salute", is also mildly taboo and can result in the spreading of infections as well. Habitual as well as fast or rough nose wiping may also result in a crease (known as a transverse nasal crease or groove) running across the nose, and can lead to permanent physical deformity observable in childhood and adulthood. Nose fetishism (or nasophilia) is the sexual partialism for the nose. ==Neanderthals==

Clive Finlayson of the Gibraltar Museum said the large Neanderthal noses were an adaptation to the cold, Todd C. Rae of the American Museum of Natural History said primate and arctic animal studies have shown sinus size reduction in areas of extreme cold rather than enlargement in accordance with Allen's rule. Miquel Hernández of the Department of Animal Biology at the University of Barcelona said the "high and narrow nose of Eskimos and Neanderthals" is an "adaptation to a cold and dry environment", since it contributes to warming and moisturizing the air and the "recovery of heat and moisture from expired air". ==See also==