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Human Nose
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 shape of the nose is determined by the nasal bones and the nasal cartilages, including the nasal septum which separates the nostrils and divides the nasal cavity into two. On average the nose of a male is larger than that of a female. The nose has an important function in breathing. The nasal mucosa lining the nasal cavity and the paranasal sinuses carries out the necessary conditioning of inhaled air by warming and moistening it. Nasal conchae, shell-like bones in the walls of the cavities, play a major part in this process. Filtering of the air by nasal hair in the nostrils prevents large particles from entering the lungs. Sneezing is a reflex to expel unwanted particles from the nose that irritate the mucosal lining. Sneezing can transmit infections, because aerosols are created ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Olfactory System
The olfactory system, or sense of smell, is the sensory system used for smelling ( olfaction). Olfaction is one of the special senses, that have directly associated specific organs. Most mammals and reptiles have a main olfactory system and an accessory olfactory system. The main olfactory system detects airborne substances, while the accessory system senses fluid-phase stimuli. The senses of smell and taste ( gustatory system) are often referred to together as the chemosensory system, because they both give the brain information about the chemical composition of objects through a process called transduction. Structure Peripheral The peripheral olfactory system consists mainly of the nostrils, ethmoid bone, nasal cavity, and the olfactory epithelium (layers of thin tissue covered in mucus that line the nasal cavity). The primary components of the layers of epithelial tissue are the mucous membranes, olfactory glands, olfactory neurons, and nerve fibers of the olfa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paranasal Sinuses
Paranasal sinuses are a group of four paired air-filled spaces that surround the nasal cavity. The maxillary sinuses are located under the eyes; the frontal sinuses are above the eyes; the ethmoidal sinuses are between the eyes and the sphenoidal sinuses are behind the eyes. The sinuses are named for the facial bones in which they are located. Structure Humans possess four pairs of paranasal sinuses, divided into subgroups that are named according to the bones within which the sinuses lie. They are all innervated by branches of the trigeminal nerve (CN V). * The maxillary sinuses, the largest of the paranasal sinuses, are under the eyes, in the maxillary bones (open in the back of the semilunar hiatus of the nose). They are innervated by the maxillary nerve (CN V2). * The frontal sinuses, superior to the eyes, in the frontal bone, which forms the hard part of the forehead. They are innervated by the ophthalmic nerve (CN V1). * The ethmoidal sinuses, which are formed from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nasal Vowel
A nasal vowel is a vowel that is produced with a lowering of the soft palate (or velum) so that the air flow escapes through the nose and the mouth simultaneously, as in the French vowel or Amoy []. By contrast, oral vowels are produced without nasalization. Nasalized vowels are vowels under the influence of neighbouring sounds. For instance, the [] of the word ''hand'' is affected by the following nasal consonant. In most languages, vowels adjacent to nasal consonants are produced partially or fully with a lowered velum in a natural process of assimilation and are therefore technically nasal, but few speakers would notice. That is the case in English: vowels preceding nasal consonants are nasalized, but there is no phonemic distinction between nasal and oral vowels, and all vowels are considered phonemically oral. The nasality of nasal vowels, however, is a distinctive feature of certain languages. In other words, a language may contrast oral vowels and nasalized vowels ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Olfactory Cells
An olfactory receptor neuron (ORN), also called an olfactory sensory neuron (OSN), is a sensory neuron within the olfactory system. Structure Humans have between 10 and 20 million olfactory receptor neurons (ORNs). In vertebrates, ORNs are bipolar neurons with dendrites facing the external surface of the cribriform plate with axons that pass through the cribriform foramina with terminal end at olfactory bulbs. The ORNs are located in the olfactory epithelium in the nasal cavity. The cell bodies of the ORNs are distributed among all three of the stratified layers of the olfactory epithelium. Many tiny hair-like non-motile cilia protrude from the olfactory receptor cell's dendrites. The dendrites extend to the olfactory epithelial surface and each ends in a dendritic knob from which around 20 to 35 cilia protrude. The cilia have a length of up to 100 micrometres and with the cilia from other dendrites form a meshwork in the olfactory mucus. The surface of the cilia is cover ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Olfactory Epithelium
The olfactory epithelium is a specialized epithelial tissue inside the nasal cavity that is involved in smell. In humans, it measures 9 cm2 and lies on the roof of the nasal cavity about 7 cm above and behind the nostrils. The olfactory epithelium is the part of the olfactory system directly responsible for detecting odors. Structure Olfactory epithelium consists of four distinct cell types: * Olfactory sensory neurons * Supporting cells * Basal cells * Brush cells Olfactory sensory neurons The olfactory receptor neurons are sensory neurons of the olfactory epithelium. They are bipolar neurons and their apical poles express odorant receptors on non-motile cilia at the ends of the dendritic knob, which extend out into the airspace to interact with odorants. Odorant receptors bind odorants in the airspace, which are made soluble by the serous secretions from olfactory glands located in the lamina propria of the mucosa.Ross, MH, ''Histology: A Text and Atlas'', 5th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Olfaction
The sense of smell, or olfaction, is the special sense through which smells (or odors) are perceived. The sense of smell has many functions, including detecting desirable foods, hazards, and pheromones, and plays a role in taste. In humans, it occurs when an odor binds to a receptor within the nasal cavity, transmitting a signal through the olfactory system. Glomeruli aggregate signals from these receptors and transmit them to the olfactory bulb, where the sensory input will start to interact with parts of the brain responsible for smell identification, memory, and emotion. There are many different causes for alteration, lack, or disturbance to a normal sense of smell, and can include damage to the nose or smell receptors, or central problems affecting the brain. Some causes include upper respiratory infections, traumatic brain injury, and neurodegenerative disease. History of study Early scientific study of the sense of smell includes the extensive doctoral dissertat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pathogen
In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ. The term ''pathogen'' came into use in the 1880s. Typically, the term ''pathogen'' is used to describe an ''infectious'' microorganism or agent, such as a virus, bacterium, protozoan, prion, viroid, or fungus. Small animals, such as helminths and insects, can also cause or transmit disease. However, these animals are usually referred to as parasites rather than pathogens. The scientific study of microscopic organisms, including microscopic pathogenic organisms, is called microbiology, while parasitology refers to the scientific study of parasites and the organisms that host them. There are several pathways through which pathogens can invade a host. The principal pathways have different episodic time frames, but soil has the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Respiratory Droplets
A respiratory droplet is a small aqueous droplet produced by exhalation, consisting of saliva or mucus and other matter derived from respiratory tract surfaces. Respiratory droplets are produced naturally as a result of breathing, speaking, sneezing, coughing, or vomiting, so they are always present in our breath, but speaking and coughing increase their number. Droplet sizes range from < 1 µm to 1000 µm, and in typical breath there are around 100 droplets per litre of breath. So for a breathing rate of 10 litres per minute this means roughly 1000 droplets per minute, the vast majority of which are a few micrometres across or smaller. As these droplets are suspended in air, they are all by definition s. However, large droplets (larger than about 100 µm, but depending on conditions) rapidly fal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aerosol
An aerosol is a suspension of fine solid particles or liquid droplets in air or another gas. Aerosols can be natural or anthropogenic. Examples of natural aerosols are fog or mist, dust, forest exudates, and geyser steam. Examples of anthropogenic aerosols include particulate air pollutants, mist from the discharge at hydroelectric dams, irrigation mist, perfume from atomizers, smoke, steam from a kettle, sprayed pesticides, and medical treatments for respiratory illnesses. When a person inhales the contents of a vape pen or e-cigarette, they are inhaling an anthropogenic aerosol. The liquid or solid particles in an aerosol have diameters typically less than 1 μm (larger particles with a significant settling speed make the mixture a suspension, but the distinction is not clear-cut). In general conversation, ''aerosol'' often refers to a dispensing system that delivers a consumer product from a can. Diseases can spread by means of small droplets in the breath, so ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transmission (medicine)
In medicine, public health, and biology, transmission is the passing of a pathogen causing communicable disease from an infected host individual or group to a particular individual or group, regardless of whether the other individual was previously infected. The term strictly refers to the transmission of microorganisms directly from one individual to another by one or more of the following means: * airborne transmission – very small dry and wet particles that stay in the air for long periods of time allowing airborne contamination even after the departure of the host. Particle size 5 μm. * direct physical contact – touching an infected individual, including sexual contact * indirect physical contact – usually by touching a contaminated surface, including soil (fomite) * fecal–oral transmission – usually from unwashed hands, contaminated food or water sources due to lack of sanitation and hygiene, an important transmission route in pediatrics, veterinary medicine an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reflex
In biology, a reflex, or reflex action, is an involuntary, unplanned sequence or action and nearly instantaneous response to a stimulus. Reflexes are found with varying levels of complexity in organisms with a nervous system. A reflex occurs via neural pathways in the nervous system called reflex arcs. A stimulus initiates a neural signal, which is carried to a synapse. The signal is then transferred across the synapse to a motor neuron which evokes a target response. These neural signals do not always travel to the brain, so many reflexes are an automatic response to a stimulus that does not receive or need conscious thought. Many reflexes are fine-tuned to increase organism survival and self-defense. This is observed in reflexes such as the startle reflex, which provides an automatic response to an unexpected stimuli, and the feline righting reflex, which reorients a cat's body when falling to ensure safe landing. The simplest type of reflex, a short-latency reflex, has a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sneezing
A sneeze (also known as sternutation) is a semi-autonomous, convulsive expulsion of air from the lungs through the nose and mouth, usually caused by foreign particles irritating the nasal mucosa. A sneeze expels air forcibly from the mouth and nose in an explosive, spasmodic involuntary action. This action allows for mucus to escape through the nasal cavity. Sneezing is possibly linked to sudden exposure to bright light, sudden change (fall) in temperature, breeze of cold air, a particularly full stomach, exposure to allergens, or viral infection. Because sneezes can spread disease through infectious aerosol droplets, it is recommended to cover one's mouth and nose with the forearm, the inside of the elbow, a tissue or a handkerchief while sneezing. In addition to covering the mouth, looking down is also recommended in order to change the direction of the droplets spread and avoid high concentration in the human breathing heights. The function of sneezing is to expel mucus c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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