The human nose is the protruding part of the face that bears the nostrils. The shape of the nose is determined by the nasal bones and the nasal cartilages, including the nasal septum which separates the nostrils. On average the nose of a male is larger than that of a female.
The nose has an area of specialised cells which are responsible for smelling (part of the olfactory system). Another function of the nose is the conditioning of inhaled air, warming it and making it more humid. Hairs inside the nose prevent large particles from entering the lungs. Sneezing is usually caused by foreign particles irritating the nasal mucosa, but can more rarely be caused by sudden exposure to bright light (called the photic sneeze reflex). Sneezing can transmit infections, because it creates aerosols in which the droplets can harbour microbes.
Video Human nose
Structure
The nasal root is the top 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 at the midline on the lower nasal margin, holding the cartilaginous center of the nose. Adult humans have cilia in the anterior nasal passage.
Development
At four (4) weeks of gestational development, the neural crest cells (the precursors of the nose) begin their caudad migration (from the posterior) towards the midface. Two symmetrical nasal placodes (the future olfactory epithelium) develop inferiorly, which the nasal pits then divide into the medial and the lateral nasal processes (the future upper lip and nose). The medial processes then form the septum, the philtrum, and the premaxilla of the nose; the lateral processes form the sides of the nose; and the mouth forms from the stomodeum (the anterior ectodermal portion of the alimentary tract), which is inferior to the nasal complex.
A nasobuccal membrane separates the mouth from the nose; respectively, the inferior oral cavity (the mouth) and the superior nasal cavity (the nose). As the olfactory pits deepen, said development forms the choanae, the two openings that connect the nasal cavity and the nasopharynx (upper part of the pharynx that is continuous with the nasal passages). Initially, primitive-form choanae develop, which then further develop into the secondary, permanent choanae.
At ten (10) weeks of gestation, the cells differentiate into muscle, cartilage, and bone. If this important, early facial embryogenesis fails, it might result in anomalies such as choanal atresia (absent or closed passage), medial nasal clefts (fissures), or lateral nasal clefts, nasal aplasia (faulty or incomplete development), and polyrrhinia (double nose).
This normal, human embryologic development is exceptionally important -- because the newborn infant breathes through his or her nose during the first 6 weeks of life -- thus, when a child is afflicted with bilateral choanal atresia, the blockage of the posterior nasal passage, either by abnormal bony tissue or by abnormal soft tissue, emergency remedial action is required to ensure that the child can breathe.
Maps Human nose
Function
The nose plays the major part in the olfactory system. It contains an area of specialised cells, olfactory receptor neurons responsible for the sense of smell. Another function of the nose is to warm and moisten inhaled air. Nasal hair in the nostrils traps large particles preventing their entry into the lungs. Sneezing is an important reflex initiated by irritation of the nasal mucosa to expel unwanted particles through the mouth and nose.
Clinical significance
One of the most common medical conditions involving the nose are nosebleeds (in medicine: epistaxis). Most of them occur in Kiesselbach's plexus. Nasal congestion is a common symptom of infections or other inflammations of the nasal lining (rhinitis), such as in allergic rhinitis or vasomotor rhinitis (resulting from nasal spray abuse). Most of these conditions also cause anosmia, which is the medical term for a loss of smell. This may also occur in other conditions, for example following trauma, in Kallmann syndrome or Parkinson's disease.
The nose is a common site of foreign bodies. The nose is susceptible to frostbite. Nasal flaring is a sign of respiratory distress that involves widening of the nostrils on inspiration.
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 to doctors as the danger triangle of the face.
Specific systemic diseases, infections or other conditions that may result in destruction of part of the nose (for example, the nasal bridge, or nasal septal perforation) are rhinophyma, skin cancer (for example, basal cell carcinoma), granulomatosis with polyangiitis, systemic lupus erythematosus, rheumatoid arthritis, tuberculosis, syphilis, leprosy and exposure to cocaine, chromium or toxins. The nose may be stimulated to grow in acromegaly.
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".
Some drugs can be administered nasally. Nasal administration can include nasal sprays and topical treatments.
Society and culture
Some people choose to have plastic surgery called a rhinoplasty, to change the aesthetic appearance of their nose. Nose piercings are also common, such as nostril, septum or bridge.
In New Zealand, nose pressing ("hongi") is a traditional greeting originating among the M?ori 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.
The septal cartilage of the nose can be destroyed through repeated nasal inhalation of drugs such as cocaine. This in turn can lead to more widespread collapse of the nasal skeleton.
Nose-picking is a common, mildly taboo habit. Medical risks include the spread of infections, nosebleeds and, rarely, self-induced perforation of the nasal septum. 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 fetish (or paraphilia) for the nose. The psychiatric condition of extreme nose picking is termed rhinotillexomania.
In certain Asian countries such as China, Japan, South Korea, Malaysia, Thailand and Bangladesh rhinoplasty is common to create a more developed nose bridge or "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.
Evolutionary hypotheses
Neanderthals
Clive Finlayson of the Gibraltar Museum said the large Neanderthal noses were an adaption 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. Therefore, Todd C. Rae concludes that the design of the large and prognathic Neanderthal nose was evolved for the hotter climate of the Middle East and was kept when the Neanderthals entered Europe.
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 "adaption 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".
Humans
An article published in the speculative journal Medical Hypotheses suggested that the nose is an alteration of the angle of skull following human skeletal changes due to bipedalism. This changed the shape of the skull base causing, together with change in diet, a knock-on morphological reduction in the relative size of the maxillary and mandible and through this a "squeezing" of the protrusion of the most anterior parts of the face more forward and so increasing nose prominence and modifying its shape.
The aquatic ape hypothesis relates the nose to a hypothesized period of aquatic adaptation in which the downward-facing nostrils and flexible philtrum prevented water from entering the nasal cavities. The theory is not generally accepted by mainstream scholars of human evolution.
Neoteny
Stephen Jay Gould has noted that larger noses are less neotenous, especially the large "Grecian" nose. Women have smaller noses than men due to not having increased secretion of testosterone in adolescence. Smaller noses, along with other neotenous features such as large eyes and full lips, are generally considered more attractive on women. Werner syndrome, a condition that causes the appearance of premature aging, causes a "bird-like" appearance due to pinching of the nose while, conversely, Down syndrome, a neotenizing condition, causes flattening of the nose. However, it looks more youthful and attractive.
See also
- Anatomy of the human nose
- Empty nose syndrome, a nose crippled by excessive resection of the inferior and/or middle turbinates of the nose
- Nasal sebum, the greasy substance on the outer part of the nose
- Nasion the curve part at top of nose, between eyebrows
- Nasothek
- Neti (Hatha Yoga), an Ayurvedic technique of nasal cleansing
- Sròn, the Scottish Gaelic word for nose and the name of some hills in the Scottish Highlands
References
External links
- From the Nose to the Eustachian Tube: Information, videos, tips for diving
- Your Nose: The Guardian Of Your Lungs
Source of article : Wikipedia
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