Integument Flashcards
order of layers of thick epidermis from superficial to deep
statum corneum stratum lucidum stratum granulosum stratum spinosum stratum basale
difference between thick and thin skin
thick:
- palms and soles
- less glandular components
thin:
- widespread
- glands and hair follicles
stratum basale
- physical appearance
- what does it contain
single layer of keratinocytes with stem cells
- mitotically active
- contains melanin
how is the stratum basale bound apically and basally
apically: desmosomes
basally: hemidesmosomes
stratum spinosum
- physical appearance
- what can it become
several layers thick containing polyhedral keratinocytes with spiny processes
- thickens with pressure to produce corns and calluses
stratum granulosum
- physical appearance
- what does it contain
thickest layer of non-keratinized portion of epidermis
- contains keratinocytes which contain keratohyalin granules
keratohyalin granules
contain keratohyalin which can then be involved in keratinization
also contain:
- basophilic, cystine and histadine rich proteins
- precursors to filagrin which assemble keratin into budles
filaggrin
protein that assembles keratin into bundles
stratum corneum
cells that have released their organelles and nucleus and are just filled with mature keratin; plasma membrane is coated with layer of lipids to form a water barrier
stratum lucidum
only well seen in thick skin; typically stains translucent; cells do not have organelles or nuclei
keratinocytes
predominant cells of the epidermis; produces keratins; participate in the epidermal water barrier
basal cells
synthesize keratin filaments that are grouped into bundles
tonofibrils
groups of keratin
spinous cells
where keratin synthesis continues and the synthesis of keratohyalin granules and lamellar bodies begins
lamellar bodies
fatty based granules that are released to contribute to the waterproof barrier
granular cells
discharge lamellar bodies for the water barrier; they contain keratinohyalin granules with filaggrin
filaggrin
protein that promotes aggregation of keratin filaments into tonofibrils
why do the keratinized cells have lower pH
low pH is required for losing the nucleus and other organelles so that the cells can be full of just mature keratin
where do new cells undergo division
stratum basale
melanocytes
- derived from
- where are they found
- what do they do
derived from neural crest cells; scattered within stratum basale; produce melanin and transfer it to keratinocytes
melanin
pigment protein that protects nuclei from UV radiation
epidermal melanin unit
one melanocyte maintains an association with up to 36 keratinocytes
how is melanin produced
tyrosine is oxidized by tyrosinase into DOPA, which is then polymerized into melanin
pigment donation
melanin is made in premelanosomes which become melanosomes as more melanin is produced; melanosomes then produce pseudopodia containing melanocytes and keratinocytes phagocytose these
Langerhan cells
antigen presenting cells that provide defense against pathogens; develop from monocytes
- activate t-lymphocytes
where are the langerhan cells identifiable
stratum spinosum
merkel cells
- what are they
- what do they do
epidermal cells that function in cutaneous sensation
- provide acute sensory perception in the fingertips
- reside in stratum basale
merkel cell carcinoma
highly aggressive form of skin cancer due to uncontrolled proliferation
papillary layer of dermis
loose connective tissue layer immediately beneath epidermis
- thinner collagen fibers and elastic fibers
- has vasculature and nerve endings
reticular layer of dermis
deep to papillary layer
- thick and less cellular
- thick, irregular bundles of type 1 collagen and course elastic fibers
- form Langer’s lines
Langer’s lines
correspond to the natural orientation of collagen fibers in the dermis, and are generally parallel to the orientation of the underlying muscle fibers
- used for surgical incisions (c-sections)
hypodermis (subcutaneous fascia)
adipose tissue deep to the dermis
- energy storage
- insulation
- have arrector pili muscles
arrector pili muscles
attach to hair follicles
meissner’s corpuscle
present in dermal papillae just beneath dermis; contain touch receptors responsive to low frequency stimuli
- ex: reading braille
pacinian corpuscle
found in deeper dermis and hypodermis; detects pressure or vibration; myelinated nerve ending surrounded by a capsule structure
- ex: fingertips, joints, periosteum, internal organs
free nerve endings
- where do they terminate
- what are they sensitive to
- additional function
nerve endings that lack connective tissue and terminate in the stratum granulosum
- sensitive to fine touch, head, cold, and pain
- sensitive to hair movement
- serve as mechanoreceptors
how do merocrine (eccrine) glands secrete
secretion is delivered in membrane bound vesicles to apical surface and then undergo exocytosis
- ex: sweat glands
- everywhere except lips and external genitalia
holocrine glands
secretion accumulates in the cell which causes apoptosis to occur, releasing cellular debris
- ex: sebaceous glands
how apocrine glands secrete
bud their secretions off through the plasma membrane producing extracellular membrane-bound vesicles
- ex: mammary glands
- also located at axilla, areola, nipple, skin around anus, external genitalia, ear canal
sebaceous glands
produce a lipid mixture with sebum via holocrine secretion
- lubricates and softens skin
- waterproofs skin
pilosebaceous canal
formed from sebum being discharged into the infundibulum (hair follicle)
two types of sweat (sudoriferous) glands
eccrine (merocrine)
apocrine
eccrine sweat glands
- physical appearance
- what cells are the ducts made of
- secretion is facilitated by
- subject to what kind of regulation
simple, coiled glands
- ducts are stratified cuboidal
- expulsion of secretions facilitated by myopeithelial cells
- cholinergic regulation
myoepithelial cells
facilitate expulsion of secretions in eccrine and apocrine sweat glands
components of sweat from eccrine glands
water, salt, ammonia, uric acid, and mucinogen granules
cholinergic regulation
sweating for temperature regulation purposes
apocrine sweat glands
- physical appearance
- what cells are the ducts made of
- what kind of secretion do they use
- secretion is facilitated by
- subject to what kind of regulation
large-lumen, tubular glands
- ducts are stratified cuboidal
- use merocrine secretion
- expulsion of secretions facilitated by myopeithelial cells
- subject to adrenergic regulation
adrenergic regulation
sweating when nervous, not for temp regulation
infundibulum
hair follicle; extends from surface of opening to the opening of its sebaceous gland
follicular bulge
bulge near insertion of the arrector pili muscles containing epidermal stem cells
bulb in hair follicles
expanded inferior segment of the hair follicle
- invaginated by vascularized dermal papilla
hair matrix
consists of matrix cells that rapidly divide and differentiate causing hair growth
medulla of the hair shaft
central part of the shaft; column of large, loosely connected keratinized cells
cortex of the hair shaft
largest layer of hair shaft located outside the medulla; cells are filled with hard keratin intermediate filaments
cuticle of the hair shaft
outermost layer; consists of several layers of overlapping keratinized squamous cells
nail root
the most proximal region of the nail that covers the nail matrix
nail matrix
where stem cells divide and form keratinocytes
- allow nail plate to remain attached to the nail bed
- pushed forward by continuous growth
lunula
crescent shaped white area near the nail matrix
cuticle
extension of skin covering nail root
