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- Human nose
- Physiology of the nose and paranasal sinuses
- Anatomy and physiology of the nose and the paranasal sinuses.
- The Comparative Anatomy and Physiology of the Nose and Paranasal Sinuses
NCBI Bookshelf. Caleb Freeman ; David A. Karp ; Chadi I. Authors S. Caleb Freeman 1 ; David A.
The nasal cavity refers to the interior of the nose, or the structure which opens exteriorly at the nostrils. It is the entry point for inspired air and the first of a series of structures which form the respiratory system.
These barriers provide mechanical protection from the invasion of infectious and allergenic pathogens. The nasal cavity extends from the external opening, the nostrils, to the pharynx the upper section of the throat , where it joins the remainder of the respiratory system. It is separated down the middle by the nasal septum , a piece of cartilage which shapes and separates the nostrils. Each nostril can be further divided into roof, floor, and walls. The nasal cavity can be divided into the vestibule, respiratory and olfactory sections.
Nasal vestibule The nasal vestibule is the dilated area at the nostril opening. Respiratory section The respiratory section of the nasal cavity refers to the passages through which air travels into the respiratory system. The respiratory section of each nostril contains four conchae protrusions or bumps which are also referred to as turbinate bones or lobes and are covered by the nasal mucosa.
Underlying these conchae are meatuses passages to interior body structures. The meatuses of the nasal cavity connect to the paranasal sinuses. Olfactory region The olfactory receptors receptors for smell sensations are found in this section of the nasal cavity. Para-nasal sinuses The nasal cavity is surrounded by a ring of paranasal sinuses and meatuses in the nasal cavity connect to these structures.
The sinuses develop as outgrowths of, and drain into, the nasal cavity. The mucosa of the sinuses connects to the nasal mucosa. Oral cavity The nasal cavity is separated from the oral cavity interior of the mouth by the hard palate.
For more information about the other sections of the respiratory system and how they work, see Respiratory System. The nasal mucosa , also called respiratory mucosa, lines the entire nasal cavity, from the nostrils the external openings of the respiratory system to the pharynx the uppermost section of the throat.
The external skin of the nose connects to the nasal mucosa in the nasal vestibule. A dynamic layer of mucus overlies the nasal epithelium the outermost layer of cells of the nasal mucosa. The initial one-third of the nasal cavity is lined by stratified squamous epithelium smooth epithelium consisting of flat surfaced cells , several cell layers thick.
The outmost layer of squamous cells overlies a layer of proliferative cells cell which divide and replicate to form new cells which is attached to a basement membrane, a network of tough fibres which supports the epithelium. The posterior two-thirds of the cavity is lined with pseudostratified columnar ciliated epithelium a type of epithelium in which cells arrange themselves in columns and project tiny hairs called cilia containing goblet cells mucus producing cells , and which overlies a basement membrane.
The nasal sub-mucosa underlies the basement membrane. This layer is made up of glands which secrete watery substances and mucus, nerves, an extensive network of blood vessels and cellular elements like blood plasma.
The entire mucosa is highly concentrated with blood vessels and contains large venous-like spaces; bodies which have a vein-like appearance and swell and congest in response to allergy or infection. Mucosa of the olfactory system Unlike other nasal mucosa, the epithelium of the olfactory system does not project cilia.
This mucosa contains nerves which connect to the olfactory nerve. The nasal cavity functions to allow air to enter the respiratory system upon respiration.
Structures within the cavity regulate the flow of air and particles it contains. The olfactory region of the nasal cavity regulates the sense of smell. Conchae turbinate bones The conchae turbinate bones of the nasal mucosa expand the total surface area of the mucosa and create turbulence in air entering the respiratory passage. This causes air to swirl as it moves through the nasal cavity and increases contact between infiltrating air and the nasal mucosa, allowing particles in the air to be trapped before entering other parts of the respiratory system e.
Olfactory system The olfactory system functions to process sensory information related to smell. They also secrete the pigment which gives this mucus its yellow colour. Mucus secreted by these glands dissolves odours as they enter the nose, enabling them to interact with the olfactory receptors. Paranasal sinuses The paranasal sinuses function to resonate speech and produce mucus which enters the nasal passage.
Other functions of the sinuses are not well understood. Nasolacrimal ducts The nasolacrimal ducts drain tears from the lacrimal tear ducts of the eyes, to the nasal mucosa. The nasal mucosa plays an important role in mediating immune responses to allergens and infectious particles which enter the nose. It helps prevent allergens and infections from invading the nasal cavity and spreading to other body structures, for example the lungs.
It is sticky and traps pathogens when they enter the nasal cavity. Trapping pathogens enables components of the mucus to attack and destroy the microbes. Lysozyme enzymes which breakdown bacteria is another component of the nasal mucus. It works to degrade pathogenic microbes. The epithelial or outer cells of the nasal mucosa are constantly being worn away and replaced by new cells from the underlying proliferative regenerative layer.
This provides additional protection as it ensures that pathogens which do manage to invade the outer cell layer are removed as the epithelial cells are sloughed off. However, in some individuals abnormal responses of the nasal mucosa occur and immune responses are mounted against allergens which the body does not usually recognise as pathogenic and thus does not usually mount an immune response to. In these individuals the mucosa, which usually functions to protect the body from invading microorganisms, is also thought to play a role in the pathological allergic response referred to as a type 1 hypersensitivity reaction.
This type of allergic response is mediated by B cells antibody producing cells of the immune system , which begin producing immunoglobulin type E IgE discussed further below. Epithelial cells Epithelial cells form the epithelium or surface layer of the nasal mucosa.
Historically nasal mucosa epithelial cells were thought to simply:. However, recent evidence suggests the functions of epithelial cells are much broader and that they also regulate immune responses which occur if the physical barrier fails and pathogens infiltrate cells of the nasal mucosa.
The epithelium contains antigen-binding proteins protein chain sections of an antibody that recognise and join to antigens. These proteins are involved in the processes through which allergens are presented to antigen presenting cells.
These cells are responsible for introducing pathogens to the T-lymphocyte cells T cells which in turn function to mount an immune response to destroy allergens presented to them. That is; T cells that have not previously encountered, and therefore do not yet recognise as pathogenic, the specific antigen being presented. Thus, antigen-binding proteins in the epithelium catalyse the series of processes through which T cells begin to recognise and respond to allergens.
Epithelial cells also release factors which enhance inflammatory responses. The most important of these factors are cytokines proteins which regulate the duration and intensity of immune responses. Allergens can directly activate the epithelial cells to produce an inflammatory response, or the epithelial cells may mount such a response in response to T cell recognition of the antigen.
Epithelial cells also appear be involved in the IgE-producing processes which perpetuate allergic responses discussed further below. Endothelial cells Endothelial cells are cells which line the walls of the arteries that feed the nasal mucosa. They are also involved in allergic responses. They primarily function to attract leukocytes white blood cells circulating in the blood to the site of inflammation.
Mucus glands Glands in the nasal mucosa produce a sticky mucus which moistens air and traps bacteria as they enter the respiratory passage. Cilia Cilia or small hairs which project from the epithelium and line the nasal mucosa create motions which drain mucus from the nasal passage to the throat from where it is swallowed and digested by stomach juices. The activity level of cilia is dependent on temperature and in cold temperatures cilia become less active.
Mucus may accumulate in and drip from the nostrils runny nose in these conditions. Underlying blood vessels The thin walled veins on which the nasal mucosa rests function to warm air entering the respiratory passage. Due to the high concentration of blood vessels in the nasal cavity, changes in these blood vessels contribute to nasal congestion.
For example, constriction of these blood vessels decreases airway resistance, making it easier for air to enter the respiratory system. The nasal nerves also regulate the congestion response. Nerves Innervation of the nasal mucosa is regulated by the trigeminal and maxillary nerves which also provide sensations to other areas of the face. The different types of nerves found in the nasal cavity and mucosa have various functions. For example, constriction of blood vessels which feed the nasal cavity is regulated in part by the sympathetic nervous system, while the parasympathetic nervous system plays a role in regulating secretions of mucus from nasal glands.
Other nerves in the nasal cavity influence the dilation of blood vessels, nasal secretions, inflammation and interactions between nerves and the mast cells which mediate allergic responses. Venous-like spaces Venous-like spaces found throughout the nasal mucosa swell and become congested in response to allergens and infection. Allergic rhinitis is a response of the nasal passages to specific allergens which is mediated by the antibody IgE. It is amongst the most common allergies in children and adults.
It is a type 1 hypersensitivity reaction which occurs when the nasal mucosa becomes sensitised to a specific environmental allergen. Common environmental allergens which cause rhinitis include mites, pollen, animals and fungi.
In individuals with a normally functioning immune system, exposure to particles in the environment such as dust or pollen does not cause an immune response. In allergic individuals, exposure to a specific allergen catalyses an irregular and hypersensitive immune response. It involves systemic body wide and localised in the nasal mucosa production of IgE antibody which specifically recognises the type of particle e.
IgE is produced by B cells in the nasal mucosa. The IgE antibodies produced inhabit immune system cells called mast cells and basophils which would not normally consider the particles e.
When IgE inhabits the mast cells and basophils it sensitises them to the specific type of particle antigen. With future exposure to the antigen, sensitised individuals experience an abnormal and pathological inflammatory response and often also experience a similar reaction to unrelated allergens like tobacco smoke. Mast cells, which form part of the immune system and mediate the inflammatory response, are abundant in the nasal mucosa of sensitised allergic individuals, but not in non-allergic individuals.
In these individuals unlike in non-allergic individuals mast cells in the nasal mucosa function to:. The more basophils that are found in the nasal mucosa, the greater the severity of allergic symptoms of allergic rhinitis.
Eosinophils , a type of white blood cell, are recruited from bone marrow to infiltrate the nasal mucosa. These cells contain numerous inflammatory factors, including a range of cytokines. They are more highly concentrated in the nasal secretions of individuals undergoing allergic reaction. The function of T helper cells, which regulate normal immune function, is also impaired in individuals affected by allergic rhinitis. Early phase immune response The inflammatory response of the nasal mucosa in allergic rhinitis can be separated into early and late phases.
The early phase is mast cell-regulated and characterised by infiltration of the nasal mucosa by the allergen e.
Physiology of the nose and paranasal sinuses
This article is only available in the PDF format. Download the PDF to view the article, as well as its associated figures and tables. In a monograph on the comparative anatomy and physiology of the larynx appeared. The anatomic and physiological investigations on which this monograph was based took seven or eight years and were made at various institutions, among them the Zoological Society, the Museum of the Royal College of Surgeons in London, and the laboratories of Kings College. This study on the mechanism of the larynx throughout the animal kingdom, its interrelation with olfaction, respiration, phonation, and possibly other functions, was pains-takingly undertaken. All this, presumably in his spare time, was done by one whose chief interest was that of a practitioner and "student" of the ear, nose, and throat in health and disease.
A secretory mucosa and unobstructed mucociliary transport are essential to respiratory and olfactory functions of the nose, and to health of the nasal cavities and the paranasal sinuses. The ostiomeatal complex within the narrow cleft of the middle meatus is susceptible to obstructions of mucociliary flow from the sinuses. Mucosal swelling, polyps, and altered properties of secretion that result from common nasal disorders can impair mucociliary clearance, and sinus disease is a common consequence. Imaging studies have demonstrated that inflammatory nasal disease is frequently accompanied by sinusitis, and the converse has been verified in a large proportion of cases. Nonlaminar characteristics of inspiratory air flow are induced by the constricted lumen of the nasal valve and entrained through the airways leading to the lungs.
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Anatomy and physiology of the nose and the paranasal sinuses.
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The human nose is the most protruding part of the face. It bears the nostrils and is the first organ of the respiratory system. It is also the principal organ in the olfactory system.
The nasal cavity refers to the interior of the nose, or the structure which opens exteriorly at the nostrils. It is the entry point for inspired air and the first of a series of structures which form the respiratory system. These barriers provide mechanical protection from the invasion of infectious and allergenic pathogens.
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The Comparative Anatomy and Physiology of the Nose and Paranasal Sinuses
The aim of this study is to evaluate the sinonasal complex to identify the main findings and to determine the diseases in this area. An accurate analysis of the local extent and tumoral dissemination through computed tomography and magnetic resonance imaging plays a significant role in the therapeutic planning, also affecting the prognosis. Keywords: Nasal sinuses; Computed tomography; Magnetic resonance imaging.
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