Diferencia entre revisiones de «Piel - Anatomía & Fisiología»
(Página creada con '==Desarrollo== ===Origen de la Epidermis=== Después de neurulación, el precursor de la epidermis está formada por las células que cubren el embrión - el '''ectodermo'''. ...') |
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*'''Las Células de Langerhans''' | *'''Las Células de Langerhans''' | ||
| − | Estas son las células dendríticas derivadas de [[Médula Osea|médula ósea]]. Actúan como [[Peyer's Patches - Anatomía & Fisiología#Células M|células presentadoras de antígenos]] en la epidermis, siendo parte del sistema inmunológico mononuclear fagocítico. Las células de Langerhans expresan moléculas MHC I y II y los receptores Fc de inmunoglobulinas y son una característica clave de las '''respuestas de hipersensibilidad retardada.''' | + | Estas son las células dendríticas derivadas de [[Médula Osea - Anatomía & Fisiología|médula ósea]]. Actúan como [[Peyer's Patches - Anatomía & Fisiología#Células M|células presentadoras de antígenos]] en la epidermis, siendo parte del sistema inmunológico mononuclear fagocítico. Las células de Langerhans expresan moléculas MHC I y II y los receptores Fc de inmunoglobulinas y son una característica clave de las '''respuestas de hipersensibilidad retardada.''' |
*'''Melanocitos''' | *'''Melanocitos''' | ||
| Línea 49: | Línea 49: | ||
*'''Las Glándulas Sudoríparas''' | *'''Las Glándulas Sudoríparas''' | ||
| − | + | Sweat is considered to be the product of [[Necrosis - Patología#Apoptosis|apoptosis]] releasing cell contents into the gland lumen, together with secretion where exocytosis, microapocrine blebbing, transcellular and perhaps paracellular processes involved in varying degrees. Sweat is composed of secretions and cellular debris and includes inorganic ions, water, immunoglobulins, amino acids and waste products including urea and lactic acid. Equine sweat is rich in proteins including glycoproteins, albumin and gammaglobulins, which cause the sweat to froth and the horse is said to "lather up". | |
| − | + | Sweat is degraded by bacteria leading to odour. Dogs and cats produce very little sweat and use panting to lower body temperature. | |
| − | *[[ | + | *[[Mammary Gland - Anatomía & Fisiología|'''Mammary glands''']] |
| − | + | These are greatly modified, enlarged sweat glands and are present in both male and female animals. Depending on species, they extend from the axillae to the groin, associated with teats and a complex array of sinuses and ducts. Age, pregnancy and [[Sistema Endocrino - Anatomía & Fisiología|endocrine]] factors have an important role in determining glandular activity. | |
| − | *''' | + | *'''Sebaceous glands''' |
| − | + | One or more sebaceous glands surround each '''hair follicle''' at a point about 1/3 of its length beneath the skin's surface. Each gland is composed of numerous ''acini'' attached to a common '''excretory duct''' through which they discharge their secretions ('''sebum''') onto the hair shaft and epidermis. In the skin and eyelids such glands release the cell contents together with secretory products with holocrine secretion. This secretion involves [[Necrosis - Pathology#Apoptosis|apoptosis]] in which the secretory products and cell debris are released into the gland lumen. The secretory products vary from species to species and include various fatty acids, diglycerides, cholesterol, diesters, wax esters and giant-ring lactones. | |
| − | + | The function of sebum is that of an emolient of the hair and skin, preventing excessive dryness. It may combine with '''sweat''' to form an emulsion within the stratum corneum and a form of cement around the hair pores preventing bacterial invasion of the epidermis. Sebum is also released from the glands during piloerection, as the action of the [[Pelo - Anatomía & Fisiología#Tipos de Pelo|arrector pili]] muscle squeezes the gland as it raises the hair. | |
| − | + | In sheep, sebum is often referred to as "'''lanolin'''". This is the cause of many skin allergies in humans. | |
| − | *''' | + | *'''Circumanal and supracaudal tail glands''' |
| − | + | Hepatoid sebaceous glands restricted to the perineum, dorsal tail and prepuce, they may have an endocrine and/or pheromone function. They empty into special sweat glands. | |
| − | *''' | + | *'''Submental and circumoral glands''' |
| − | + | Large glands in the [[Labios|lip]] region of cats and some rodents; presumed to have a territory marking role. Circumoral glands are enlarged integumentary glands bordering on the mucocutaneous junctions of the mouth or oral margins associated with greeting and related behaviours, especially in scuiriomorph rodents. | |
'''Rabbits''' have scent glands on the chin which are used to mark territory by excreting droplets onto structures in the environment. Male rabbits scent-mark more intensively than female rabbits, and dominant individuals more than subdominant animals. This is correlated with larger scent glands in dominant males. | '''Rabbits''' have scent glands on the chin which are used to mark territory by excreting droplets onto structures in the environment. Male rabbits scent-mark more intensively than female rabbits, and dominant individuals more than subdominant animals. This is correlated with larger scent glands in dominant males. | ||
| − | *''' | + | *'''Inguinal glands''' |
| − | + | Sexually-related scent glands prominent in ungulates. They are located at the base of the udders to allow offspring to locate the teats of their mother. | |
'''Rabbits''' have pocket-like inguinal glands lateral to the genital openings. They are used to mark kits and cage surfaces and may contain dried yellow-brown sebaceous material. Does will attack young which have not been scent-marked, even if they are in the same breeding group. | '''Rabbits''' have pocket-like inguinal glands lateral to the genital openings. They are used to mark kits and cage surfaces and may contain dried yellow-brown sebaceous material. Does will attack young which have not been scent-marked, even if they are in the same breeding group. | ||
| − | *[[Ano - Anatomía & Fisiología#Diferencias Entre las Especies|''' | + | *[[Ano - Anatomía & Fisiología#Diferencias Entre las Especies|'''Anal glands''']] |
| − | + | Sebaceous (and modified apocrine in the dog) glands lie within the wall of the anal sacs, with a duct carrying material to the anal opening. The foul smelling secretion may act as a territorial marker. Secretions are expressed on defecation. The secretions are composed of fatty and serous materials with cellular debris. | |
'''Rabbits''' also have anal glands which coat the faeces and are used by rabbits to scent-mark their territory. | '''Rabbits''' also have anal glands which coat the faeces and are used by rabbits to scent-mark their territory. | ||
| − | == | + | ==Cutaneous Appendages== |
| − | === | + | ===Footpads=== |
[[image: Section of Dog Footpad.jpg|thumb|250px|right|Thickened skin of the canine footpad. ©RVC2008]] | [[image: Section of Dog Footpad.jpg|thumb|250px|right|Thickened skin of the canine footpad. ©RVC2008]] | ||
| − | + | Cats and Dogs have a digitigrade stance with digital, metacarpal and metatarsal pads in contact with the ground. A carpal pad is also present, but seems to be superfluous. | |
| − | + | Pads are covered with a very thickened epidermis with no hair follicles. They are hyperpigmented and have atrichial sweat glands opening to the surface under the influence of epinephrine. | |
| − | + | There is little dermis and the hypodermis is composed of collagenous and elastic fibres mixed with adipose tissue to form a digital cushion that provides protection from mechanical impact. | |
| − | === | + | ===The Nose=== |
| − | + | The covering of the nose is very thickened with rete ridges providing anchoring. The surface has a cobblestone appearance in dogs and cats. Hair and sebaceous glands are absent, atrichial glands are present. | |
| − | [[image: The nose of a Dog.jpg|thumb|200px|left| | + | [[image: The nose of a Dog.jpg|thumb|200px|left|The cobblestone appearance of the nose of the Dog. Courtesy of Piotr Grzywocz]] |
| − | === | + | ===Claws=== |
| − | + | Claws have a variety of functions including locomotion, climbing, fighting and hunting. They are composed of a coronary band, lateral compressed walls and a flaky ventral sole. The hard keratinised epidermis is formed from the nail matrix that is an extension of the hirsute skin, with an underlying vascular dermis. | |
| − | + | Cats can unsheath their claws by muscle action and retract them with an elastic ligament on the dorsal aspect of the middle and distal phalanges. | |
| − | + | Depending on the pigmentation of the claw, the dermis may or may not be visible. Care must be taken when clipping claws to avoid laceration of the 'quick' and subsequent haemorrhage. | |
The claws of the accessory first digits on the medial aspect of the foot of dogs is often termed the '''dew claw'''. | The claws of the accessory first digits on the medial aspect of the foot of dogs is often termed the '''dew claw'''. | ||
| − | === | + | ===Eyelids=== |
| − | + | The palpebral margin is thicker than the remainder of the eyelid and cilia grow from the margin. There are various glands in the region, including '''Moll's glands''' that are modified sweat glands, associated with the cilia. '''Meibomian glands, Zeis glands''' associated with the cilia and the '''lacrimal glands''' together produce the tear film. | |
==Inmunología== | ==Inmunología== | ||
| − | + | The immune system is involved in several diseases of the skin, with different types of hypersensitivity reactions occuring. | |
| − | + | See also [[:Categoría:Sistema Integumentario - Immunologic Pathology|Skin Immunology]] | |
==Diferencias Entre las Especies== | ==Diferencias Entre las Especies== | ||
Revisión del 18:20 26 sep 2011
Desarrollo
Origen de la Epidermis
Después de neurulación, el precursor de la epidermis está formada por las células que cubren el embrión - el ectodermo. Esto se divide después en dos capas, la externa que forma la peridermis y la interna que forma la capa basal o estrato basal. Una capa adicional se forma a partir de la capa basal y es llamada capa espinosa o estrato espinoso. Las capas basal y espinosa que son denominadas la capa de Malphigian, y contiene las células que luego se dividen para producir la capa granular o estrato granuloso. Conforme las células de la capa granular se diferencian y queratinizan, van formando la capa exterior de la capa córnea o stratum corneum.
Estructura y Función
Epidermis
La epidermis es un epitelio escamoso estratificado compuesto de cuatro capas de células y anclado en una lámina basal de tejido conectivo. Los queratinocitos migran a través de la epidermis desde la capa basal. Esta migración se inicia en el estrato basal, luego se mueve hacia arriba a través del estrato espinoso, estrato granuloso y el estrato córneo.
- Estrato basal
La capa más profunda de la epidermis es la capa basal. Se compone de una sola capa de epitelio columnar que está adherido a la lámina basal. La nutrición es suministrada por los capilares subyacentes de la dermis. Migración de las células hacia la superficie comienza aquí.
- Estrato espinoso
Se localiza por encima de la capa basal. Las células espinosas son grandes células poligonales con grandes filamentos desmosómicas intercelulares, que actúan como puente entre las células. Cuando las células se mueven en esta capa, se contraen y se separan. La queratinización comienza en el estrato espinoso y continúa en el estrato granuloso.
- Estrato Granuloso
Hacia el exterior del estrato espinoso, se encuentra el estrato granuloso. Las células granulares son queratinocitos delgados y aplanados con gránulos de queratohialina de prominencia variable. En su superficie exterior, el estrato granuloso secreta llamada los cuerpos lamelares, que están compuestos de lípidos y enzimas que se fusionan con la membrana plasmática y ayudan a formar el gradiente de concentración de agua que lleva a la pérdida de agua transepidérmica.
- Estrato Córneo
La capa externa, el estrato córneo, se compone de células anucleadas, delgadas y llenas de filamentos de queratina y proteínas que forman una envoltura celular resistente a los solventes y las enzimas, así como una barrera de permeabilidad al agua y los iones. Las células del estrato córneo están incrustadas en una matriz rica en lípidos que ayuda a mantener las células en conjunto, mientras que los desmosomas que estaban presentes en las capas inferiores han desaparecido. Para mantener el espesor del estrato córneo constante, hay una constante exfoliación de corneocitos, que son reemplazados por nuevos corneocitos. Las enzimas de los cuerpos lamelares de la estrato granulosa ayudan a romper el 'pegamento' de los lípidos intercelulares que mantiene las células en su lugar y también hay una cierta degradación de los desmosomas.
Las Células de la Epidermis
- Las Células de Langerhans
Estas son las células dendríticas derivadas de médula ósea. Actúan como células presentadoras de antígenos en la epidermis, siendo parte del sistema inmunológico mononuclear fagocítico. Las células de Langerhans expresan moléculas MHC I y II y los receptores Fc de inmunoglobulinas y son una característica clave de las respuestas de hipersensibilidad retardada.
- Melanocitos
Estas son también las células dendríticas y se derivan de la cresta neural. Están inmersos en la epidermis donde forman un estrecho contacto con un número definido de queratinocitos. La melanina está compuesta de dos tipos: la eumelanina, que es negra-marrón y la feomelanina, que es de color marrón rojizo. Los melanocitos producen el pigmento en los melanosomas, que son estructuras de membrana implicados en la transferencia de pigmento a los queratinocitos. Una función importante de la melanina es la protección a los rayos UV y la ausencia de pigmento confiere mayor sensibilidad a los mismos.
- Las Células de Merkel
Son parte del aparato sensorial de la piel y se encuentran en el estrato basal de la epidermis, donde actúan como mecanorreceptores de adaptación lenta. Por lo general, están estrechamente asociadas con las fibras nerviosas aferentes mielinizadas, las cuales se disponen en una estructura en forma de placa en la base de las células de Merkel, formando en conjunto un corpúsculo de Merkel.
Dermis
La epidermis se comunica con la dermis subyacente en la zona de la membrana basal (BMZ). Este enlace incluye las uniones de anclaje denominadas hemidesmosomas y adhesiones focales. Los primeros comprenden la matriz extracelular (ECM) de proteínas como laminina-5 y el colágeno tipo IV que forman parte de la lámina densa BMZ, mientras que la lámina lúcida está compuesta por colágeno tipo V. El colágeno tipo VII es importante en la formación de fibrillas de anclaje entre la dermis y la lámina basal.
Las crestas son proyecciones de la epidermis hacia la dermis en zonas de carga mecánica, como la trufa y las almohadillas.
La dermis está formada por tejido fibroso denso compuesto de colágeno tipo I, III and V, con algunas fibras de elastina, y proporciona una matriz de apoyo para el transporte de los vasos sanguíneos, vasos linfáticos, los nervios y los receptores sensoriales, los folículos pilosos, las glándulas sebáceas y sudoríparas y la distribución de células blancas.
Glándulas
- Las Glándulas Sudoríparas
Sweat is considered to be the product of apoptosis releasing cell contents into the gland lumen, together with secretion where exocytosis, microapocrine blebbing, transcellular and perhaps paracellular processes involved in varying degrees. Sweat is composed of secretions and cellular debris and includes inorganic ions, water, immunoglobulins, amino acids and waste products including urea and lactic acid. Equine sweat is rich in proteins including glycoproteins, albumin and gammaglobulins, which cause the sweat to froth and the horse is said to "lather up".
Sweat is degraded by bacteria leading to odour. Dogs and cats produce very little sweat and use panting to lower body temperature.
These are greatly modified, enlarged sweat glands and are present in both male and female animals. Depending on species, they extend from the axillae to the groin, associated with teats and a complex array of sinuses and ducts. Age, pregnancy and endocrine factors have an important role in determining glandular activity.
- Sebaceous glands
One or more sebaceous glands surround each hair follicle at a point about 1/3 of its length beneath the skin's surface. Each gland is composed of numerous acini attached to a common excretory duct through which they discharge their secretions (sebum) onto the hair shaft and epidermis. In the skin and eyelids such glands release the cell contents together with secretory products with holocrine secretion. This secretion involves apoptosis in which the secretory products and cell debris are released into the gland lumen. The secretory products vary from species to species and include various fatty acids, diglycerides, cholesterol, diesters, wax esters and giant-ring lactones.
The function of sebum is that of an emolient of the hair and skin, preventing excessive dryness. It may combine with sweat to form an emulsion within the stratum corneum and a form of cement around the hair pores preventing bacterial invasion of the epidermis. Sebum is also released from the glands during piloerection, as the action of the arrector pili muscle squeezes the gland as it raises the hair.
In sheep, sebum is often referred to as "lanolin". This is the cause of many skin allergies in humans.
- Circumanal and supracaudal tail glands
Hepatoid sebaceous glands restricted to the perineum, dorsal tail and prepuce, they may have an endocrine and/or pheromone function. They empty into special sweat glands.
- Submental and circumoral glands
Large glands in the lip region of cats and some rodents; presumed to have a territory marking role. Circumoral glands are enlarged integumentary glands bordering on the mucocutaneous junctions of the mouth or oral margins associated with greeting and related behaviours, especially in scuiriomorph rodents.
Rabbits have scent glands on the chin which are used to mark territory by excreting droplets onto structures in the environment. Male rabbits scent-mark more intensively than female rabbits, and dominant individuals more than subdominant animals. This is correlated with larger scent glands in dominant males.
- Inguinal glands
Sexually-related scent glands prominent in ungulates. They are located at the base of the udders to allow offspring to locate the teats of their mother.
Rabbits have pocket-like inguinal glands lateral to the genital openings. They are used to mark kits and cage surfaces and may contain dried yellow-brown sebaceous material. Does will attack young which have not been scent-marked, even if they are in the same breeding group.
Sebaceous (and modified apocrine in the dog) glands lie within the wall of the anal sacs, with a duct carrying material to the anal opening. The foul smelling secretion may act as a territorial marker. Secretions are expressed on defecation. The secretions are composed of fatty and serous materials with cellular debris.
Rabbits also have anal glands which coat the faeces and are used by rabbits to scent-mark their territory.
Cutaneous Appendages
Footpads
Cats and Dogs have a digitigrade stance with digital, metacarpal and metatarsal pads in contact with the ground. A carpal pad is also present, but seems to be superfluous.
Pads are covered with a very thickened epidermis with no hair follicles. They are hyperpigmented and have atrichial sweat glands opening to the surface under the influence of epinephrine.
There is little dermis and the hypodermis is composed of collagenous and elastic fibres mixed with adipose tissue to form a digital cushion that provides protection from mechanical impact.
The Nose
The covering of the nose is very thickened with rete ridges providing anchoring. The surface has a cobblestone appearance in dogs and cats. Hair and sebaceous glands are absent, atrichial glands are present.
Claws
Claws have a variety of functions including locomotion, climbing, fighting and hunting. They are composed of a coronary band, lateral compressed walls and a flaky ventral sole. The hard keratinised epidermis is formed from the nail matrix that is an extension of the hirsute skin, with an underlying vascular dermis.
Cats can unsheath their claws by muscle action and retract them with an elastic ligament on the dorsal aspect of the middle and distal phalanges.
Depending on the pigmentation of the claw, the dermis may or may not be visible. Care must be taken when clipping claws to avoid laceration of the 'quick' and subsequent haemorrhage.
The claws of the accessory first digits on the medial aspect of the foot of dogs is often termed the dew claw.
Eyelids
The palpebral margin is thicker than the remainder of the eyelid and cilia grow from the margin. There are various glands in the region, including Moll's glands that are modified sweat glands, associated with the cilia. Meibomian glands, Zeis glands associated with the cilia and the lacrimal glands together produce the tear film.
Inmunología
The immune system is involved in several diseases of the skin, with different types of hypersensitivity reactions occuring.
See also Skin Immunology
Diferencias Entre las Especies
As the integument of avians, reptiles and amphibians is markedly different to that of mammals, it is covered on another page.
The Integument of Exotic Species
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Este artículo ha sido traducido de Inglés por 'Gregorio Puga Barlón' - 16.09.2011. |