Skin Flashcards
Celulas de la epidermis
Queratenocitos
Melanocitos
Celulas de Langerhans
Celulas de Merkel
Celula oval o cubica adherida a la lamina basal que conforme madura produce una proteina llamada queratina acumulándose dentro del citoplasma, una vez que llego al estrato más alto pierde sus organelas y el nucleo y lo único que queda es escamas de queratina
Queratenocitos
El más bajo y adherido a la lamina basal, mitoticamente activo, en esta estrato se acumula la melanina producida por el melanocito
Estrato basal
Estrato con el mayor número de capas o niveles llegando a tener de 6 a 8 niveles de Queratenocitos en una piel normal, son las que van a producir polipeptidos (desmoplaquina y desmogleinas) que forman los desmosomas dandole el aspecto espinoso, entre mas pegado al estrato basal es poligonal mientras madura se alarga hacia los lados
Estrato esponjoso
Formado por 1 a 3 niveles de Queratenocitos conteniendo granulos de queratohialina
Estrato granuloso
Está formado por múltiples capas de celulas poliedricas que se disponen en un patrón de canasta, estas celulas pierden sus nucleos y organelas citoplasmaticas y se componen por filamentos de queratina, se observa como una capa rosada y en donde hay piel gruesa como la planta de los pies y palmas
Estrato lucido o cornificado
Formado por todas las capas de queratina desprendidas por el estrato lucido que puede ser inexistente como en los párpados
Corneo
El proceso de queratenizacion en condiciones normales
20 a 45 días
Grosor del estrato lucido en las callosidades o plantas de los pies
1 cm
Celulas dendriticas que derivan de la cresta neural, se ven vaculadas en su citoplasma y se ubican en la capa basal de la epidermis con nucleo ovoide y producen melanina
Melanocitos
Diferentes tipos de melanina
Feomelanina cuando es rojo
Eumelanina Amarillo negruzco
Función principal de la melanina
Protección de los rayos UV
Personas que con defecto en la maquinaria enzimatica de la tirosinasa produciendo manchas blancas debido a la ausencia de Melanocitos
Vitiligo
La cantidad de Melanocitos
1 melanocitos por cada 10 queratinocitos
Celulas observables en los estratos espinoso y granuloso indistinguibles una de otra
Celulas de Merkel y Langerhans
Se encuentran siempre en la capa basal con Queratenocitos teñidos de melanina observables como raíces color café
Melanocitos
Función relacionada con el tacto, se localiza en los pulpejos, labios y cavidad oral de aspecto parecido a melanocito, se adhieren a Queratenocitos por desmosomas con una zona para nuclear densa formada por granulos formado por neuritas no mielinizadas
Celulas de Merkel
Celulas dendriticas derivadas de monocitos, parecido a melanocito pero con nucleo con muescas generalmente presente en estrato espinoso y puede presentar cuerpos alargados que en ocasiones uno de sus extremos se dilata dando aspecto de raqueta llamados cuerpos raquetoides o granulos de Birbeck
Celulas de langerhans
Marcador especial para Melanocitos
HMB 45
Anticuerpo para marcar celulas de Langerhans
CD1a
Anticuerpos para celulas de Merkel
Enolasa neurona especifica
Peptido intestinal vasoactivo
Encefalina
La piel se divide en tres capas principales
Epidermis
Dermis
Hipodermis
The largest single organ of the body
Skin
Weight of the skin
15% to 20% of total weight body
Skin surface of the external environment
1.5 to 2 m2
Origin of epidermis
Ectodermal
Origin of dermis
Mesoderm
At the irregular junction between the dermis and epidermis projection called
Dermal papillae
Dermal papillae interdigitate with invaginating
Epidermal ridges
Specific function of the skin
Protection Sensory Thermoregulatory Metabolic Sexual signaling
Cells of skin through the local action of UV light on the vitamins precursor, that need calcium metabolism and proper bone formation, they synthesized
Vitamin D
Excess electrolytes can be remove in
Sweat
Subcutaneous layer stores a significant amount of …. In form of fats
Energy
Dermal epidermal interdigitation forms ridges and grooves called
Dermatoglyphs, or fingerprint,
Thickness od the epidermal layer
75 to 150 micrometers for thin skin
400 to 1400 micrometers or 1.4 mm for thick skin
Full skin on the back is about
4 mm
Join basal layer to the basal lamina by
Hemidesmosomes
The human epidermis is renewed about every
15 to 30 days
The cytoeskeletal keratins intermediate filaments about … In diameter
10 nm
Is normal the thickest layer
Spinous layer
Percentage of all cancers originate in the skin
One third
Consist of 15 to 20 layers of squamous keratinized cells fill with keratins
Stratum corneum
Dense non membrane bound masses of filaggrin and other proteins
Keratohyaline granules
Keratocytes are typically produced and differentiate at accelerated rates causing at least slight thickening of the epidermal layers caused by overactive T lymphocytes that trigger An autoimmune reaction in the skin
Psoriasis
Factors that give color to skin
Melanin and carotene
Proportion of melanocytes
One melanocytes accumulate for every five or six basal keratinocytes
600 -1200 /mm2
Tyrosinase activity converts tyrosine into
3,4 dihydroxyphenilalanine DOPA
Melanin pigment is accumulated in granules called
Melanosomes
Melanosomes are transported vía …. To the tips of the cytoplasmatic extensions
Kinesin
Melanosomes are phagocytose by neighboring keratinocytes and transport by …. Toward their nuclei
Dynein
Melanin depot
Keratinocytes
One melanocytes ➕ keratinocytes where is transfer Melanosomes Make up
Epidermal melanin unit
The density of such unit skin is
Similar for all individuals
2-3 layers of anucleate dead cells seen only in thick skin
Stratum lucidum
Langerhans cells present,several layers of keratinocytes all joined by desmosomes
Stratum spinosum
Melanocytes and Merkel cells present
Basal layer
Compose of areolar or loose connective tissue and adipose connective tissue
Subcutaneous layer
Darkening of the skin, or tanning after exposure to solar radiation at wavelengths of …….. A physicochemical reaction darkens preexisting melanin
290 to 320 nm
Los lunares son crecimientos sobre la piel. Se producen cuando las células productoras de pigmento de la piel, llamadas melanocitos, crecen en grupos
Lunares
Numero de lunares que tiene una persona
La mayoría de las personas tiene entre 10 y 40 lunares.
Represent 2% to 8% of the epidermal cells
Langerhans cells
Are abundant in highly sensitive skin like fingertips and the basal of some hair folicles, essential for light touch sensation joined by desmosomes of the basal epidermal layer originate from stem cells as keratinocytes
Merkel cells
Are very aggressive and difficult to treat and is 40 times less common than malignant melanoma but twice the mortality of that disease
Merkel cells carcinomas
Stage of melanosome formation in which Accumulate of tyrosinase in vesicles and granular matrix proteins
Stage I Melanosomes
Stage of melanosome formation matrix has Been organized into parallel filaments
Stage II
Stage of melanosome formation melanin is deposited and accumulates
Stage III
Stage of melanosome formation has lost tyrosinase and other activities and has the internal matrix completely filled with melanin
Stage IV
Is a composite structure consisting of the basal lamina and the reticular lamina always occurs between the stratum basale and the dermis
Basement membrane
Abnormalities of the dermal epidermal juntion
Bullous pemphigoid
Includes the dermal papillae, consist of loose connective tissue with types I and III collagen fibers and achoring fibrils of type VII collagen insert in to the basal lamina helping to bind the dermis to the epidermis
Papillary layer
Two sublayers with indistinct boundaries rich network of blood and lymphatic vessels
Papillary layers
Reticular layers
Sublayer of dermis much thicker with dense connective tissue (collagen type I) with more fibers and elastic fibers abundant proteoglycans
Reticular layer
Capillary branches extend into the dermal papillae forming a rich nutritive capillary network just below the epidermis
Subpapilary plexus
Unencapsulated receptors includes
Merkel cells
Free nerve ending
Root hair plexuses
Associated with expanded nerve ending function as tonic receptors for sustain light touch and for sensitive objects texture
Merkel cells
In the papillary dermis and extended into lower epidermal layers which responds to high and low temperatures pain and itching and function as tactile receptor
Free ending receptors
Encapsulated receptors that are seen in routine preparations
Meissner corpuscles and lamellated (pacinan) corpuscles
Encapsulated receptors
Meissner corpuscles
lamellated (pacinan) corpuscles
Krause
Ruffini
Loss of tactile corpuscles or reduction in their activity can also be detected in
Scleroderma
Elliptical structures 30 to 75 micrometers by 50 to 150 micrometers within Shwann cells arranged initiate impulses when light touch or low frequency stimuli declining after puberty
Meissner corpuscles
Large oval structures aproximately 0.5 mm by 1mm found deep in reticular dermis and hypodermis with An outer capsule and 15 -50 thin concentric lamellae of Shwann cells specialized for sensing coarse touch, pressure and vibration also located in organs like wall of rectum and urinary bladder producing sensation of pressure when is distored
Lamellated pacinian corpuscle
Simpler encapsulated with extremely thin collagen capsule penetrated by a sensory fiber primary found on the penis and clitoris when they sense low frequency vibrations
Krause end bulb
Have collagenous fusiform capsules with sensory stimulated by stretch (tension) or twisting (torque) in the skin
Ruffini corpuscles
Glabrous skin
Palms Soles, Lips Glans penis Clitoris And labia minora
The face hair has about
600 hairs/cm2
The remainder of the body has about
60/cm2
The growing hair follicle has a terminal dilation called a
Hair bulb
Inserts into the base of the hair bulb and contain a capillary network required to sustain the hair follicle
Dermal papilla
Melanocytes in the hair bulb transfer Melanosomes into the epithelial cells that will later differentiate to form
Hair
In most thick hairs large, vacuolated, and moderately keratinized cells form the central
Medulla
Densely packed cells Make un…. That surround the medulla
Cortex
Thin layer of heavily queratinized squamous cells covers the cortex
Cuticle
The outmost cells of the hair bulb are continous with epithelial root sheath
Internal and external root sheath
Completely surrounds the initial part of the hair root but degenerates above the level of the attached sebaceous glands
Internal root sheath
Extended all the way to the epidermis where it is continous with the basal and spinous layers
External root sheath
Separating the hair follicle from the dermis is An acellular Hyaline layer called
Glassy membrane
Hairs grow asynchronously, three major phases
Anagen
Catagen
Telogen
A generally long period of mitotic activity and growth of hair
Anagen
A brief period of arrested growth and regression of the hair bulb
Catagen
A finally long period of inactivity of hair
Telogen
Hair growth on the face and pubis is influenced by
Sex hormones, especially androgens and begins at puberty
Loss of hair a complex combinations of genetic and hormonal factors
Alopecia
Hard plates of keratin on the dorsal surface of distal phalanx
Nails
Proximal part of the nail is the
Nail root
Nail root is covered by a fold of skin from which the epidermal stratum corneum extend as the
Cuticle or eponychium
Is bound to a bed of epidemis the nail bed which contains only the basal and spinous epidermal layers
Nail plate
The nail root forms from the
Nail matrix
Continuous growth in nail matrix in fingernails at a rate
3 mm/mo
Continuous growth in nail matrix in toenails at a rate
1 mm/mo
The distal end of the plate becomes free of the nail bed at the epidermal fold called
Hyponychium
Average of glands per square centimeters of skin
100
In the face and scalp sebaceous glands per square centimeters of skin
400 - 900/cm2
A hair follicle and its sebaceous glands Make up a
Pilosebaceous unit
Hairless regions, in which sebaceous ducts open directly onto the epidermal surface
Penis
Clitoris
Eyelids
Nipples
Acini of sebaceous glands are
Holocrine secretion
Flattened epithelial cells of holocrine glands on the basal lamina which proliferate and displace centrally called
Sebocytes
Is a complex mixture of lipids that are hydrolyzed by bacterial enzymes after secretion
Sebum
Sebaceous glands stimulated by
Testosterone men
Ovarian and adrenal androgens in women
Two types of Sweat glands
Apocrine and eccrine
Are the most numerous Sweat glands on the foot soles 620/cm2
Eccrine sweat glands
The secretory part of eccrine Sweat glands has epithelium
Stratified cuboidal epithelium
Three cell types on eccrine Sweat glands
Clear cells
Dark cells
Myoepithelial cells
Produce the Sweat and the interstitial fluid comes from the capillary rich dermis
Clear cells
Undergo merocrine secretion yo realease a poorly mixture of glycoprotein with bactericidal activity
Dark cells
Absorbs Na ions from secreted water to prevent excessive loss of this electrolytes
Ducts
Are largely confined to skin of the axilary and perineal regions, with much longer lumen, secretion in initially odorless but may acquire a distinctive odor as a result of bacterial activity and pheromones
Apocrine Sweat glands
When the Sweat is often salty
Cystic fibrosis