In a multicellular organism , an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life , an organ lies between tissue and an organ system . Tissues are formed from same type cells to act together in a function. Tissues of different types combine to form an organ which has a specific function. The intestinal wall for example is formed by epithelial tissue and smooth muscle tissue . Two or more organs working together in the execution of a specific body function form an organ system, also called a biological system or body system.
101-444: An ear is the organ that enables hearing and (in mammals) body balance using the vestibular system . In mammals, the ear is usually described as having three parts: the outer ear , the middle ear and the inner ear . The outer ear consists of the pinna and the ear canal . Since the outer ear is the only visible portion of the ear in most animals, the word "ear" often refers to the external part alone. The middle ear includes
202-408: A haematoma around the perichondrium , which can impair blood supply and healing. Owing to its exposed position, the external ear is susceptible to frostbite as well as skin cancers , including squamous-cell carcinoma and basal-cell carcinomas . The ear drum may become perforated in the event of a large sound or explosion, when diving or flying (called barotrauma ), or by objects inserted into
303-446: A chemical neurotransmitter when stimulated. Sound waves moving through fluid flows against the receptor cells of the organ of Corti. The fluid pushes the filaments of individual cells; movement of the filaments causes receptor cells to become open to receive the potassium -rich endolymph. This causes the cell to depolarise, and creates an action potential that is transmitted along the spiral ganglion , which sends information through
404-508: A complicated relief on its inner surface and a fairly smooth configuration on its posterior surface. A tubercle , known as Darwin's tubercle , is sometimes present, lying in the descending part of the helix and corresponding to the ear-tip of mammals. The earlobe consists of areola and adipose tissue . The symmetrical arrangement of the two ears allows for the localisation of sound . The brain accomplishes this by comparing arrival-times and intensities from each ear, in circuits located in
505-399: A many-lobed berry), in which multiple glands branch off a central duct. The glands deposit sebum on the hairs and bring it to the skin surface along the hair shaft . The structure, consisting of hair, hair follicles, arrector pili muscles, and sebaceous glands, is an epidermal invagination known as a pilosebaceous unit . Sebaceous glands are also found in hairless areas ( glabrous skin ) of
606-461: A method of reprimand or punishment – "In Roman times, when a dispute arose that could not be settled amicably, the injured party cited the name of the person thought to be responsible before the Praetor; if the offender did not appear within the specified time limit, the complainant summoned witnesses to make statements. If they refused, as often happened, the injured party was allowed to drag them by
707-405: A number of arteries. The posterior auricular artery provides the majority of the blood supply. The anterior auricular arteries provide some supply to the outer rim of the ear and scalp behind it. The posterior auricular artery is a direct branch of the external carotid artery, and the anterior auricular arteries are branches from the superficial temporal artery . The occipital artery also plays
808-409: A person moves, these otoliths shift position. This shift alters the positions of the filaments, which opens ion channels within the cell membranes, creating depolarisation and an action potential that is transmitted to the brain along the vestibulocochlear nerve. Dynamic balance is provided through the three semicircular canals. These three canals are orthogonal (at right angles) to each other. At
909-399: A person to sense acceleration. Static balance is provided by two ventricles, the utricle and the saccule. Cells lining the walls of these ventricles contain fine filaments, and the cells are covered with a fine gelatinous layer. Each cell has 50–70 small filaments, and one large filament, the kinocilium . Within the gelatinous layer lie otoliths , tiny formations of calcium carbonate . When
1010-410: A role. The middle ear is supplied by the mastoid branch of either the occipital or posterior auricular arteries and the deep auricular artery , a branch of the maxillary artery . Other arteries which are present but play a smaller role include branches of the middle meningeal artery , ascending pharyngeal artery , internal carotid artery , and the artery of the pterygoid canal . The inner ear
1111-423: A sheet of sweat that is not readily lost in drops of sweat. This is of importance in delaying dehydration. In colder conditions, the nature of sebum becomes more lipid, and in coating the hair and skin, rain is effectively repelled. Sebum is produced in a holocrine process , in which cells within the sebaceous gland rupture and disintegrate as they release the sebum and the cell remnants are secreted together with
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#17327658949911212-479: A similar composition to human sebaceous glands, are androgen responsive, and have been used as a basis for study. Some species of bat, including the Mexican free-tailed , have a specialized sebaceous gland occurring on the throat called a "gular gland". This gland is present more frequently in males than females, and it is hypothesized that the secretions of the gland are used for scent-marking. Sebaceous adenitis
1313-409: A type of sebaceous gland that secrete a special type of sebum into tears . Surrounding the female nipples , areolar glands are specialized sebaceous glands for lubricating the nipples. Fordyce spots are benign, visible, sebaceous glands found usually on the lips , gums and inner cheeks , and genitals . In humans, sebaceous glands are found throughout all areas of the skin, except the palms of
1414-416: A variety of organ systems . These specific systems are widely studied in human anatomy . The functions of these organ systems often share significant overlap. For instance, the nervous and endocrine system both operate via a shared organ, the hypothalamus . For this reason, the two systems are combined and studied as the neuroendocrine system . The same is true for the musculoskeletal system because of
1515-687: A whole, are referred to as the Organon because logic is a tool for philosophical thinking. Earlier thinkers, such as those who wrote texts in the Hippocratic corpus , generally did not believe that there were organs of the body but only different parts of the body. Some alchemists (e.g. Paracelsus ) adopted the Hermetic Qabalah assignment between the seven vital organs and the seven classical planets as follows: Chinese traditional medicine recognizes eleven organs, associated with
1616-429: A working ear, human deafness (extreme insensitivity to sound) most commonly occurs because of abnormalities of the inner ear, rather than in the nerves or tracts of the central auditory system. Providing balance, when moving or stationary, is also a central function of the ear. The ear facilitates two types of balance: static balance, which allows a person to feel the effects of gravity , and dynamic balance, which allows
1717-470: A year) throughout life, with the increase in length more extreme in males. Ears are individually very unique, with the odds of two people having matching ears very low. Additionally, the ear's proportions are normally retained for life, and have thus been employed for forensic identification since the 1950s. Hearing loss may be either partial or total. This may be a result of injury or damage, congenital disease , or physiological causes. When hearing loss
1818-430: Is a microscopic exocrine gland in the skin that opens into a hair follicle to secrete an oily or waxy matter, called sebum , which lubricates the hair and skin of mammals . In humans, sebaceous glands occur in the greatest number on the face and scalp , but also on all parts of the skin except the palms of the hands and soles of the feet . In the eyelids , meibomian glands , also called tarsal glands, are
1919-489: Is a result of injury or damage to the outer ear or middle ear, it is known as conductive hearing loss . When deafness is a result of injury or damage to the inner ear, vestibulochoclear nerve, or brain, it is known as sensorineural hearing loss . Causes of conductive hearing loss include an ear canal blocked by earwax, ossicles that are fixed together or absent, or holes in the eardrum. Conductive hearing loss may also result from middle ear inflammation causing fluid build-up in
2020-431: Is an obstruction. Reconstructive surgery to treat hearing loss is considered as an option for children older than five, with a cosmetic surgical procedure to reduce the size or change the shape of the ear is called an otoplasty . The initial medical intervention is aimed at assessing the baby's hearing and the condition of the ear canal, as well as the middle and inner ear. Depending on the results of tests, reconstruction of
2121-510: Is not a disease but a symptom that can result from a number of underlying causes. One of the most common causes is noise-induced hearing loss . Other causes include: ear infections , disease of the heart or blood vessels , Ménière's disease , brain tumors , emotional stress , exposure to certain medications, a previous head injury , and earwax. It is more common in those with depression and anxiety. The ears have been ornamented with jewelry for thousands of years, traditionally by piercing of
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#17327658949912222-427: Is partly composed of sebum produced by glands in the ear canal. These secretions are viscous and have a high lipid content, which provides good lubrication. Sebaceous glands are involved in skin problems such as acne and keratosis pilaris . In the skin pores, sebum and keratin can create a hyperkeratotic plug called a comedo . Acne is a common occurrence, particularly during puberty in teenagers , and
2323-425: Is passed as a signal to the brain along the vestibulocochlear nerve. Dynamic balance also helps maintain eye tracking when moving, via the vestibulo–ocular reflex . During embryogenesis , the ear develops as three distinct structures: the inner ear, the middle ear and the outer ear. Each structure originates from a different germ layer : the ectoderm , endoderm and mesenchyme . Around its second to third week,
2424-511: Is separate from that of the middle and external ear. Middle ear anomalies can occur because of errors during head and neck development. The first pharyngeal pouch syndrome associates middle ear anomalies to the malleus and incus structures as well as to the non-differentiation of the annular stapedial ligament . Temporal bone and ear canal anomalies are also related to this structure of the ear and are known to be associated with sensorineural hearing loss and conductive hearing loss. Vertigo refers to
2525-428: Is supplied by the anterior tympanic branch of the maxillary artery; the stylomastoid branch of the posterior auricular artery; the petrosal branch of middle meningeal artery; and the labyrinthine artery , arising from either the anterior inferior cerebellar artery or the basilar artery . Sound waves travel through the outer ear, are modulated by the middle ear, and are transmitted to the vestibulocochlear nerve in
2626-498: Is the parenchyma , whereas the stroma includes the nerves that innervate the parenchyma, the blood vessels that oxygenate and nourish it and carry away its metabolic wastes, and the connective tissues that provide a suitable place for it to be situated and anchored. The main tissues that make up an organ tend to have common embryologic origins, such as arising from the same germ layer . Organs exist in most multicellular organisms . In single-celled organisms such as members of
2727-406: Is the placenta , which has evolved more than 100 times independently in vertebrates, has evolved relatively recently in some lineages, and exists in intermediate forms in extant taxa. Studies on the evolution of the placenta have identified a variety of genetic and physiological processes that contribute to the origin and evolution of organs, these include the re-purposing of existing animal tissues,
2828-435: Is the hearing of sound when no external sound is present. While often described as a ringing, it may also sound like a clicking, hiss or roaring. Rarely, unclear voices or music are heard. The sound may be soft or loud, low pitched or high pitched and appear to be coming from one ear or both. Most of the time, it comes on gradually. In some people, the sound causes depression, anxiety, or concentration difficulties. Tinnitus
2929-445: Is thought to relate to an increased production of sebum due to hormonal factors. The increased production of sebum can lead to a blockage of the sebaceous gland duct. This can cause a comedo (commonly called a blackhead or a whitehead ), which can lead to infection, particularly by the bacteria Cutibacterium acnes . This can inflame the comedones, which then change into the characteristic acne lesions. Comedones generally occur on
3030-413: Is very mild, balsamic, and intended to wet and lubricate the mouth". In The Principles of Physiology 1834, Andrew Combe noted that the glands were not present in the palms of the hands or soles of the feet. The preputial glands of mice and rats are large modified sebaceous glands that produce pheromones used for territorial marking. These and the scent glands in the flanks of hamsters have
3131-412: The alkaline nature of contaminants. Sebaceous lipids help maintain the integrity of the skin barrier and supply vitamin E to the skin. During the last three months of fetal development , the sebaceous glands of the fetus produce vernix caseosa , a waxy white substance that coats the skin to protect it from amniotic fluid . The areolar glands are in the areola that surrounds the nipple in
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3232-449: The auricle (the visible portion of the ear). The ears of vertebrates are placed somewhat symmetrically on either side of the head, an arrangement that aids sound localization . The ear develops from the first pharyngeal pouch and six small swellings that develop in the early embryo called otic placodes , which are derived from the ectoderm . The ear may be affected by disease, including infection and traumatic damage. Diseases of
3333-401: The earlobe . In ancient and modern cultures, ornaments have been placed to stretch and enlarge the earlobes, allowing for larger plugs to be slid into a large fleshy gap in the lobe. Tearing of the earlobe from the weight of heavy earrings , or from traumatic pull of an earring (for example, by snagging on a sweater), is fairly common. Injury to the ears has been present since Roman times as
3434-415: The eukaryotes , the functional analogue of an organ is known as an organelle . In plants, there are three main organs. The number of organs in any organism depends on the definition used. There are approxiamately 79 Organs in the human body,but it is something that is debated as not all scientist agree on what counts as an organ. Except for placozoans , multicellular animals including humans have
3535-428: The eyelids , nose , penis , labia minora , the inner mucosal membrane of the cheek , and nipples . Some sebaceous glands have unique names. Sebaceous glands on the lip and mucosa of the cheek, and on the genitalia, are known as Fordyce spots , and glands on the eyelids are known as meibomian glands . Sebaceous glands of the breast are also known as Montgomery's glands . Sebaceous glands are first visible from
3636-404: The facial nerve , which also supplies sensation to the skin of the ear itself, as well as to the external ear cavity. The great auricular nerve , auricular nerve , auriculotemporal nerve , and lesser and greater occipital nerves of the cervical plexus all supply sensation to parts of the outer ear and the surrounding skin. The auricle consists of a single piece of elastic cartilage with
3737-421: The five Chinese traditional elements and with yin and yang , as follows: The Chinese associated the five elements with the five planets (Jupiter, Mars, Venus, Saturn, and Mercury) similar to the way the classical planets were associated with different metals. The yin and yang distinction approximates the modern notion of solid and hollow organs. Sebaceous gland A sebaceous gland or oil gland
3838-446: The hands and soles of the feet . There are two types of sebaceous glands: those connected to hair follicles and those that exist independently. Sebaceous glands are found in hair-covered areas, where they are connected to hair follicles . One or more glands may surround each hair follicle, and the glands themselves are surrounded by arrector pili muscles , forming a pilosebaceous unit. The glands have an acinar structure (like
3939-418: The haruspices or the augurs in order to divine the future by their shape, dimensions or other factors. This practice remains an important ritual in some remote, tribal societies. The term "visceral" is contrasted with the term " parietal ", meaning "of or relating to the wall of a body part, organ or cavity " The two terms are often used in describing a membrane or piece of connective tissue, referring to
4040-421: The homeobox gene family such as Pax , Msx and Otx homeobox genes. The development of inner ear structures such as the cochlea is regulated by Dlx5 / Dlx6 , Otx1 / Otx2 and Pax2 , which in turn are controlled by the master gene Shh . Shh is secreted by the notochord . The middle ear and its components develop from the first and second pharyngeal arches . The tympanic cavity and auditory tube develop from
4141-400: The neural crest . Eventually, cells from the tissue surrounding the ossicles will experience apoptosis and a new layer of endodermal epithelial will constitute the formation of the tympanic cavity wall. Unlike structures of the inner and middle ear, which develop from pharyngeal pouches, the ear canal originates from the dorsal portion of the first pharyngeal cleft . It is fully expanded by
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4242-473: The scala vestibuli , the scala tympani and the scala media . Both the scala vestibuli and the scala tympani contain an extracellular fluid called perilymph , while the scala media contains endolymph. The vestibular membrane and the basilar membrane develop to separate the cochlear duct from the vestibular duct and the tympanic duct, respectively. Most of the genes responsible for the regulation of inner ear formation and its morphogenesis are members of
4343-417: The stomach , intestines , gallbladder , bladder , and rectum . In the thoracic cavity , the heart is a hollow, muscular organ. Splanchnology is the study of the viscera. The term "visceral" is contrasted with the term " parietal ", meaning "of or relating to the wall of a body part, organ or cavity ". The two terms are often used in describing a membrane or piece of connective tissue, referring to
4444-447: The superior olivary complex and the trapezoid bodies , which are connected via pathways to both ears. The middle ear lies between the outer ear and the inner ear. It consists of an air-filled cavity called the tympanic cavity and includes the three ossicles and their attaching ligaments; the auditory tube ; and the round and oval windows . The ossicles are three small bones that function together to receive, amplify, and transmit
4545-402: The tympanic cavity and the three ossicles . The inner ear sits in the bony labyrinth , and contains structures which are key to several senses: the semicircular canals , which enable balance and eye tracking when moving; the utricle and saccule , which enable balance when stationary; and the cochlea , which enables hearing. The ear canal is cleaned via earwax , which naturally migrates to
4646-445: The vestibular system , as well as the cochlea of the auditory system . The outer ear is the external portion of the ear and includes the fleshy visible auricle , the ear canal, and the outer layer of the eardrum (also called the tympanic membrane). The auricle consists of the curving outer rim called the helix , the inner curved rim called the antihelix , and opens into the ear canal. The tragus protrudes and partially obscures
4747-431: The vestibule contains two small fluid-filled recesses, the utricle and saccule. These connect to the semicircular canals and the cochlea. There are three semicircular canals angled at right angles to each other which are responsible for dynamic balance. The cochlea is a spiral shell-shaped organ responsible for the sense of hearing. These structures together create the membranous labyrinth . The bony labyrinth refers to
4848-429: The 13th to the 16th week of fetal development , as bulgings off hair follicles. Sebaceous glands develop from the same tissue that gives rise to the epidermis of the skin. Overexpression of the signalling factors Wnt , Myc and SHH all increase the likelihood of sebaceous gland presence. The sebaceous glands of a human fetus secrete a substance called vernix caseosa , a waxy, translucent white substance coating
4949-461: The 20th century, organ transplants began to take place as scientists knew more about the anatomy of organs. These came later in time as procedures were often dangerous and difficult. Both the source and method of obtaining the organ to transplant are major ethical issues to consider, and because organs as resources for transplant are always more limited than demand for them, various notions of justice, including distributive justice , are developed in
5050-441: The acquisition of new functional properties by these tissues, and novel interactions of distinct tissue types. The study of plant organs is covered in plant morphology . Organs of plants can be divided into vegetative and reproductive. Vegetative plant organs include roots , stems , and leaves . The reproductive organs are variable. In flowering plants , they are represented by the flower , seed and fruit . In conifers ,
5151-581: The amount of sebum produced by the sebaceous glands. Should the usual treatments fail, the presence of the Demodex mite could be looked for as the possible cause. Other conditions that involve the sebaceous glands include: The word sebaceous , meaning 'consisting of sebum', was first termed in 1728 and comes from the Latin for 'tallow'. Sebaceous glands have been documented since at least 1746 by Jean Astruc , who defined them as "...the glands which separate
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#17327658949915252-410: The antihelix, antitragus, and earlobe. The outer ears develop in the lower neck . As the mandible forms, they move towards their final position level with the eyes. The ears of newborn humans are proportionally very large, even more so than the head's largeness as compared to the body. Ears grow quickly until about the age of nine, then continue to grow steadily in circumference (about 0.5 millimeters
5353-459: The apparatus necessary to change the vibrations transmitted from the outside world via the middle ear into signals passed along the vestibulocochlear nerve to the brain. The hollow channels of the inner ear are filled with liquid, and contain a sensory epithelium that is studded with hair cells . The microscopic "hairs" of these cells are structural protein filaments that project out into the fluid. The hair cells are mechanoreceptors that release
5454-504: The areas with more sebaceous glands, particularly the face, shoulders, upper chest and back. Comedones may be "black" or "white" depending on whether the entire pilosebaceous unit, or just the sebaceous duct, is blocked. Sebaceous filaments —innocuous build-ups of sebum—are often mistaken for whiteheads . There are many treatments available for acne from reducing sugars in the diet, to medications that include antibiotics, benzoyl peroxide, retinoids, and hormonal treatments. Retinoids reduce
5555-418: The auditory portion of the vestibulocochlear nerve to the temporal lobe of the brain. The human ear can generally hear sounds with frequencies between 20 Hz and 20 kHz ( the audio range ). Sounds outside this range are considered infrasound (below 20 Hz) or ultrasound (above 20 kHz) Although hearing requires an intact and functioning auditory portion of the central nervous system as well as
5656-414: The auricle are common. These anomalies include chromosome syndromes such as ring 18 . Children may also present cases of abnormal ear canals and low ear implantation. In rare cases, no auricle is formed ( atresia ), or is extremely small ( microtia ). Small auricles can develop when the auricular hillocks do not develop properly. The ear canal can fail to develop if it does not channelise properly or if there
5757-423: The body. Sapienic acid is a sebum fatty acid that is unique to humans, and is implicated in the development of acne. Sebum is odorless, but its breakdown by bacteria can produce strong odors. Sex hormones are known to affect the rate of sebum secretion; androgens such as testosterone have been shown to stimulate secretion, and estrogens have been shown to inhibit secretion. Dihydrotestosterone acts as
5858-426: The bony compartment which contains the membranous labyrinth, contained within the temporal bone. The inner ear structurally begins at the oval window, which receives vibrations from the incus of the middle ear. Vibrations are transmitted into the inner ear into a fluid called endolymph , which fills the membranous labyrinth. The endolymph is situated in two vestibules, the utricle and saccule, and eventually transmits to
5959-401: The bony labyrinth. Around the 28th day, parts of the otic vesicle begin to form the vestibulocochlear nerve. These form bipolar neurons , which supply sensation to parts of the inner ear (namely the sensory parts of the semicircular canals, macular of the utricle and saccule, and organ of Corti). Around the 33rd day, the vesicles begin to differentiate. Posteriorly, they form what will become
6060-411: The cochlea, a spiral-shaped structure. The cochlea consists of three fluid-filled spaces: the vestibular duct , the cochlear duct , and the tympanic duct . Hair cells responsible for transduction —changing mechanical changes into electrical stimuli are present in the organ of Corti in the cochlea. The blood supply of the ear differs according to each part of the ear. The outer ear is supplied by
6161-445: The developing embryo consists of three layers: ectoderm, mesoderm , and endoderm. The first part of the ear to develop is the inner ear, which begins to form from the ectoderm around the embryo's 22nd day, derived from two thickenings called otic placodes on either side of the head. Each otic placode recedes below the ectoderm, forms an otic pit and then an otic vesicle . This entire mass is eventually surrounded by mesenchyme to form
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#17327658949916262-597: The ear and to pinch them hard if they resisted. Hence the French expression " se faire tirer l’oreille ", of which the literal meaning is "to have one's ear pulled" and the figurative meaning "to take a lot of persuading". We use the expression "to tweak (or pull) someone's ears" to mean "inflict a punishment"." The auricles have an effect on facial appearance. In Western societies, protruding ears (present in about 5% of ethnic Europeans ) have been considered unattractive, particularly if asymmetric. The first surgery to reduce
6363-429: The ear canal, as does the facing antitragus . The hollow region in front of the ear canal is called the concha. The ear canal stretches for about 1 inch (2.5 cm). The first part of the canal is surrounded by cartilage , while the second part near the eardrum is surrounded by bone . This bony part is known as the auditory bulla and is formed by the tympanic part of the temporal bone . The ear canal ends at
6464-479: The ear may lead to hearing loss , tinnitus and balance disorders such as vertigo , although many of these conditions may also be affected by damage to the brain or neural pathways leading from the ear. The ear has been adorned by earrings and other jewelry in numerous cultures for thousands of years, and has been subjected to surgical and cosmetic alterations. The human ear consists of three parts—the outer ear , middle ear and inner ear . The ear canal of
6565-430: The ear structures (the temporal bone) can also cause damage to the middle ear. A cholesteatoma is a cyst of squamous skin cells that may develop from birth or secondary to other causes such as chronic ear infections. It may impair hearing or cause dizziness or vertigo, and is usually investigated by otoscopy and may require a CT scan. The treatment for cholesteatoma is surgery. There are two principal damage mechanisms to
6666-416: The ear. Another common cause of injury is due to an infection such as otitis media. These may cause a discharge from the ear called otorrhea , and are often investigated by otoscopy and audiometry . Treatment may include watchful waiting , antibiotics and possibly surgery, if the injury is prolonged or the position of the ossicles is affected. Skull fractures that go through the part of the skull containing
6767-406: The eardrum, where it is connected at its longest part (the manubrium or handle) by a ligament. It transmits vibrations to the incus, which in turn transmits the vibrations to the small stapes bone. The wide base of the stapes rests on the oval window. As the stapes vibrates, vibrations are transmitted through the oval window, causing movement of fluid within the cochlea . The round window allows for
6868-432: The eardrum. The malleus rests on the membrane, and receives the vibration. This vibration is transmitted along the incus and stapes to the oval window. Two small muscles, the tensor tympani and stapedius , also help modulate noise. The two muscles reflexively contract to dampen excessive vibrations. Vibration of the oval window causes vibration of the endolymph within the vestibule and the cochlea. The inner ear houses
6969-416: The end of each canal is a slight enlargement, known as the ampulla , which contains numerous cells with filaments in a central area called the cupula . The fluid in these canals rotates according to the momentum of the head. When a person changes acceleration, the inertia of the fluid changes. This affects the pressure on the cupula, and results in the opening of ion channels. This causes depolarisation, which
7070-422: The end of the 18th week of development. The eardrum is made up of three layers (ectoderm, endoderm and connective tissue). The auricle originates as a fusion of six hillocks. The first three hillocks are derived from the lower part of the first pharyngeal arch and form the tragus, crus of the helix, and helix, respectively. The final three hillocks are derived from the upper part of the second pharyngeal arch and form
7171-572: The estimated numbers of persons with hearing difficulty (11%) and the percentage of those that can be attributed to occupational noise exposure (24%). Furthermore, according to the National Health and Nutrition Examination Survey (NHANES), approximately twenty-two million (17%) US workers reported exposure to hazardous workplace noise. Workers exposed to hazardous noise further exacerbate the potential for developing noise-induced hearing loss when they do not wear hearing protection . Tinnitus
7272-402: The ethical analysis. This situation continues as long as transplantation relies upon organ donors rather than technological innovation, testing, and industrial manufacturing. The English word "organ" dates back to the twelfth century and refers to any musical instrument. By the late 14th century, the musical term's meaning had narrowed to refer specifically to the keyboard-based instrument . At
7373-483: The external surface of the eardrum, while the surrounding skin contains ceruminous and sebaceous glands that produce protective earwax . Earwax naturally migrates outward through ear canal, constituting a self-cleaning system. Two sets of muscles are associated with the outer ear: the intrinsic and extrinsic muscles. In some mammals, these muscles can adjust the direction of the pinna. In humans, these muscles have little or no effect. The ear muscles are supplied by
7474-407: The eyes are closed, and their lipid quality also prevents the eyelids from sticking together. They attach directly to the follicles of the eyelashes, which are arranged vertically within the tarsal plates of the eyelids. Fordyce spots , or Fordyce granules, are ectopic sebaceous glands found on the genitals and oral mucosa . They show themselves as yellowish-white milia (milk spots). Earwax
7575-432: The fat." He describes them in the oral cavity and on the head , eyelids , and ears , as "universally" acknowledged. Astruc describes them being blocked by "small animals" that are "implanted" in the excretory ducts and attributes their presence in the oral cavity to apthous ulcers , noting that "these glands naturally [secrete] a viscous humour, which puts on various colours and consistencies... in its natural state
7676-465: The female breast. These glands secrete an oily fluid that lubricates the nipple, and also secrete volatile compounds that are thought to serve as an olfactory stimulus for the newborn. During pregnancy and lactation these glands, also called Montgomery's glands, become enlarged. Meibomian glands , in the eyelids , secrete a form of sebum called meibum onto the eye , that slows the evaporation of tears . They also serve to create an airtight seal when
7777-436: The first part of the pharyngeal pouch between the first two arches in an area which will also go on to develop the pharynx . This develops as a structure called the tubotympanic recess . The ossicles (malleus, incus and stapes) normally appear during the first half of fetal development. The first two (malleus and incus) derive from the first pharyngeal arch and the stapes derives from the second. All three ossicles develop from
7878-399: The fluid within the inner ear to move. As the stapes pushes the secondary tympanic membrane , fluid in the inner ear moves and pushes the membrane of the round window out by a corresponding amount into the middle ear. The ossicles help amplify sound waves by nearly 15–20 times. The inner ear sits within the temporal bone in a complex cavity called the bony labyrinth . A central area known as
7979-445: The hearing loss is severe or prolonged. Hearing aids work by amplifying the sound of the local environment and are best suited to conductive hearing loss. Cochlear implants transmit the sound that is heard as if it were a nervous signal, bypassing the cochlea. Active middle ear implants send sound vibrations to the ossicles in the middle ear, bypassing any non-functioning parts of the outer and middle ear. Anomalies and malformations of
8080-449: The inappropriate perception of motion. This is due to dysfunction of the vestibular system . One common type of vertigo is benign paroxysmal positional vertigo , when an otolith is displaced from the ventricles to the semicircular canal. The displaced otolith rests on the cupola, causing a sensation of movement when there is none. Ménière's disease , labyrinthitis , strokes , and other infective and congenital diseases may also result in
8181-425: The inner ear in industrialised society, and both injure hair cells. The first is exposure to elevated sound levels (noise trauma), and the second is exposure to drugs and other substances ( ototoxicity ). A large number of people are exposed to sound levels on a daily basis that are likely to lead to significant hearing loss . The National Institute for Occupational Safety and Health has recently published research on
8282-417: The inner ear. This nerve transmits information to the temporal lobe of the brain, where it is registered as sound. Sound that travels through the outer ear impacts on the eardrum, and causes it to vibrate. The three ossicles bones transmit this sound to a second window (the oval window ), which protects the fluid-filled inner ear. In detail, the pinna of the outer ear helps to focus a sound, which impacts on
8383-468: The liver and heart evolved in the chordates about 550-500 million years ago, while the gut and brain are even more ancient, arising in the ancestor of vertebrates, insects, molluscs, and worms about 700–650 million years ago. Given the ancient origin of most vertebrate organs, researchers have looked for model systems, where organs have evolved more recently, and ideally have evolved multiple times independently. An outstanding model for this kind of research
8484-467: The new generation of plants (see clonal colony ). Many societies have a system for organ donation , in which a living or deceased donor's organ are transplanted into a person with a failing organ. The transplantation of larger solid organs often requires immunosuppression to prevent organ rejection or graft-versus-host disease . There is considerable interest throughout the world in creating laboratory-grown or artificial organs . Beginning in
8585-445: The normally air-filled space, such as by otitis media . Tympanoplasty is the general name of the operation to repair the middle ear's eardrum and ossicles. Grafts from muscle fascia are ordinarily used to rebuild an intact eardrum. Sometimes artificial ear bones are placed to substitute for damaged ones, or a disrupted ossicular chain is rebuilt in order to conduct sound effectively. Hearing aids or cochlear implants may be used if
8686-435: The oily, waxy substance called sebum ( Latin : fat, tallow ) that is made of triglycerides , wax esters , squalene , and metabolites of fat-producing cells. Sebum lubricates the skin and hair of mammals. Sebaceous secretions in conjunction with apocrine glands also play an important thermoregulatory role. In hot conditions, the secretions emulsify the sweat produced by the eccrine sweat glands and this produces
8787-403: The opposing sides. Aristotle used the word frequently in his philosophy, both to describe the organs of plants or animals (e.g. the roots of a tree, the heart or liver of an animal) because, in ancient Greek, the word ' organon ' means 'tool', and Aristotle believed that the organs of the body were tools for us by means of which we can do things. For similar reasons, his logical works, taken as
8888-406: The opposing sides. The organ level of organisation in animals can be first detected in flatworms and the more derived phyla , i.e. the bilaterians . The less-advanced taxa (i.e. Placozoa , Porifera , Ctenophora and Cnidaria ) do not show consolidation of their tissues into organs. More complex animals are composed of different organs, which have evolved over time. For example,
8989-514: The organ that bears the reproductive structures is called a cone . In other divisions ( phyla ) of plants, the reproductive organs are called strobili , in Lycopodiophyta , or simply gametophores in mosses . Common organ system designations in plants include the differentiation of shoot and root. All parts of the plant above ground (in non- epiphytes ), including the functionally distinct leaf and flower organs, may be classified together as
9090-498: The outer ear is done in stages, with planning for any possible repairs of the rest of the ear. Approximately one out of one thousand children suffer some type of congenital deafness related to the development of the inner ear. Inner ear congenital anomalies are related to sensorineural hearing loss and are generally diagnosed with a computed tomography (CT) scan or a magnetic resonance imaging (MRI) scan. Hearing loss problems also derive from inner ear anomalies because its development
9191-483: The outer ear is separated from the air-filled tympanic cavity of the middle ear by the eardrum . The middle ear contains the three small bones—the ossicles —involved in the transmission of sound, and is connected to the throat at the nasopharynx , via the pharyngeal opening of the Eustachian tube . The inner ear contains the otolith organs—the utricle and saccule —and the semicircular canals belonging to
9292-447: The perception of vertigo. Injuries to the external ear occur fairly frequently, and can leave minor to major deformity. Injuries include: laceration , avulsion injuries , burn and repeated twisting or pulling of an ear, for discipline or torture. Chronic damage to the ears can cause cauliflower ear , a common condition in boxers and wrestlers in which the cartilage around the ears becomes lumpy and distorted owing to persistence of
9393-459: The primary androgen in the prostate and in hair follicles. Sebaceous glands are part of the body's integumentary system and serve to protect the body against microorganisms. Sebaceous glands secrete acids that form the acid mantle . This is a thin, slightly acidic film on the surface of the skin that acts as a barrier to microbes that might penetrate the skin. The pH of the skin is between 4.5 and 6.2, an acidity that helps to neutralize
9494-405: The projection of prominent ears was published in the medical literature by Ernst Dieffenbach in 1845, and the first case report in 1881. Organ (anatomy) An organ's tissues can be broadly categorized as parenchyma , the functional tissue, and stroma , the structural tissue with supportive, connective, or ancillary functions. For example, the gland 's tissue that makes the hormones
9595-413: The relationship between the muscular and skeletal systems . In the study of anatomy , viscera ( sg. : viscus ) refers to the internal organs of the abdominal , thoracic , and pelvic cavities . The abdominal organs may be classified as solid organs or hollow organs . The solid organs are the liver , pancreas , spleen , kidneys , and adrenal glands . The hollow organs of the abdomen are
9696-489: The same time, a second meaning arose, in reference to a "body part adapted to a certain function". Plant organs are made from tissue composed of different types of tissue. The three tissue types are ground, vascular, and dermal. When three or more organs are present, it is called an organ system. The adjective visceral , also splanchnic , is used for anything pertaining to the internal organs. Historically, viscera of animals were examined by Roman pagan priests like
9797-410: The sebum. The cells are constantly replaced by mitosis at the base of the duct. Sebum is secreted by the sebaceous gland in humans. It is primarily composed of triglycerides (≈41%), wax esters (≈26%), squalene (≈12%), and free fatty acids (≈16%). The composition of sebum varies across species. Wax esters and squalene are unique to sebum and not produced as final products anywhere else in
9898-409: The shoot organ system. The vegetative organs are essential for maintaining the life of a plant. While there can be 11 organ systems in animals, there are far fewer in plants, where some perform the vital functions, such as photosynthesis , while the reproductive organs are essential in reproduction . However, if there is asexual vegetative reproduction , the vegetative organs are those that create
9999-516: The skin of newborns . After birth, activity of the glands decreases until there is almost no activity during ages two–six years, and then increases to a peak of activity during puberty , due to heightened levels of androgens . Relative to keratinocytes that make up the hair follicle, sebaceous glands are composed of huge cells with many large vesicles that contain the sebum. These cells express Na and Cl ion channels, ENaC and CFTR (see Fig. 6 and Fig. 7 in reference ). Sebaceous glands secrete
10100-495: The sound from the eardrum to the inner ear. The ossicles are the malleus (hammer), incus (anvil), and the stapes (stirrup). The stapes is the smallest named bone in the body . The middle ear also connects to the upper throat at the nasopharynx via the pharyngeal opening of the Eustachian tube. The three ossicles transmit sound from the outer ear to the inner ear. The malleus receives vibrations from sound pressure on
10201-427: The utricle and semicircular canals. Anteriorly, the vesicles differentiate into a rudimentary saccule, which eventually becomes the saccule and cochlea. Part of the saccule eventually gives rise and connects to the cochlear duct, which appears approximately during the sixth week and connects to the saccule through the ductus reuniens . As the cochlear duct's mesenchyme begins to differentiate, three cavities are formed:
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