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Derm ex1
histo
21
Medical
Professional
11/19/2011

Additional Medical Flashcards

 


 

Cards

Term
how is the thickness of the skin described?
Definition
it is based on the epidermal thickness
Term

order of skin layers:

Stratum _____

Definition

from deep to superfiscial

 

basale-basile layer, cuboid to columnar, highly mitotically active, attach to hemidesmosomes

spinosum - slighly more irregular, attach to desmosomes; tonofibrils present

granulosum- diamond shaped cells containing kerotohyalin granules.  keratin granules attach to many histidine and cystidine rich protein precursors of fillagrin

lucidum- usually only in thick skin, clear thin layer

corneum- outermost, made of keratin and horny scales.  dead cells known as squame

Term
keratinocytes?
Definition

the predominate cell type of epidermis and they produce keratin which is needed to form the water barrier

-created by the deposition of insoluble proteins on the inside of the cell membrane and the outer lipid bilayer

Term
use of melanocytes
Definition

melanin containing.  located at basale layer or below, they can transfer melanin via long entensions through to the cytoplasm of keratinocytes (keratinocytes phagocytose the tips of these projections)

 

the melanin granules are protective against UV damage

 

melanocytes come from neural crest cells

Term
formation of the epidermal water barrier
Definition
stratum spinosum is producing keratohyalin granules, but is also producing lamellar bodies which get packaged and exported to fill the intercellular spaces between granulosum and the corneum where they form a lipid envelope
Term
langerhans cells
Definition

dendritic cells of mesenchymal origin found mainly in the stratum spinosum

 

express MHC I and II and uptake Ags from surface and deliver them to lymphnode

Term
merkel cells
Definition

found in stratum basale, these have enhanced sensory preception

 

bound to neighboring keratinocytes by desmosomes

 

have neurosecretory granules similar to adrenal medulla

Term
most numberous neuronal receptor in the epidermis?
Definition

free nerve endings

 

surround hair follicles (mechanoreceptors, whiskers)

 

terminate in stratum granulosum

 

for fine touch, heat and cold

Term
pacinian corpuscle
Definition

deep pressure sensors of mechanical and vibrational pressure.  deep to all dermis, goes all the way to periosteum sometimes

 

myelinated and onion appearance

 

works by having pressure or vibrations displace the capsule lamellae which depoloarizes the axon

Term
messiner corpuscle
Definition
ÒTouch receptors within dermal papillae

looks like Q-tip

especially responsive to low frequency stimuli on hairless skin
Term
ruffini corpuscle
Definition
located in the dermis, detects mechanical displacement of collagen fibers
Term
what are the layers of the dermis
Definition

the papillary layer which is thinner and composed of loose connective tissue

 

the reticular layer which is composed of dense irregular connective tissue

Term
hair follicle formation
Definition

-invagination of the epidermis down into dermis, the deepest part of which becomes the germinal matrix (regrowth center)

 

three segments

infundibulum- seg from surface to opening of sebaceous gland

isthmus- from infundibulum to arrector pilli muscle 

inferior segment- growing part

Term
germitive layer of hair growth
Definition

3 layers

cuticle: squamous cells

          -Huxleys layer: flattened cells

          - Henleys layer: cuboidal cells in direct contact  with outermost part of hair follicle, the external root sheath


Hair emerges follicle completely keratinized

Term
structure of hair shaft
Definition
ÒMedulla – central, soft keratin, large vacuolated cells; only present in thick hair
ÒCortex – peripheral to medulla, cells here undergo differentiation into keratin-filled cells;contains pigment
ÒCuticle of hair shaft – outermost layer of hair composed of very thin scale-like cells 
Term
sebaceous glands
Definition

located at the upper third of the hair follicle, they secrete sebum which oils and lubricates the cells

 

proliferation of cells in the basal layer of the gland.  these cells accumulate fatty material in their cytoplasm and eventually burst expelling the material (this is sebum).  this progess continues and can be sped up by the contraction of arrector pilli muscles.

Term

types of sweat glands

 

Definition
ÒEccrine – most common, distributed all over body except lips and part of the external genitalia.  independent from hair cells. below dermis in subQ tissue.  major role is temperature reg.  sweat is hypotonic, undergo reabsorption
ÒApocrine – limited to axilla, areola, nipple, skin around anus and external genitalia; store secretory protein.  release phermones. become fxnl at puberty.  connected to hair follicles.  do not undergo reabsorption
Term
cells in a eccrine gland
Definition
ÒClear cells – abundant glycogen, pale cytoplasm, cuboidal to simple columnar; secrete H20, NaCl, urea. Canaliculi conduct sweat to lumen of ducts
ÒDark cells – secretory granules, secrete glycoprotein (proteoglycans)
ÒMyoepithelial cells – basal aspect, oriented obliquely and longitudinally around secretory portions of tubules, spindle shaped; contractions aid in expelling sweat; the excretory duct does NOT have myoepithelial cells
Term
arrector pilli muscle
Definition

connects to connective tissue sheath of hair follicle

 

produces goosebumps and dimpling of skin, causes hair to stand on ends

Term
nails
Definition

lie on top of nail bed.  originate in 3rd month of embryological development.  stratum granulosum-less

 

epidermis of fingers and toes invade underlying dermis

 

made of hard keratin with a high sulfur content

Term
areas of nail
Definition
ÒCrescent-shaped white area near nail root – lunula: color is from thick, opaque layer of partially keratinized matrix cells
ÒEponychium (cuticle) – edge of skin fold covering nail root, also hard keratin, does not desquamate
ÒHyponychium – epidermis underlying distal tip of nail where stratum corneum of distal free edge contacts the nail; thickened epidermal layer which secures the free edge of the nail plate at fingertip
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