Chapter 2 Outline: Structure and Function of Skin Flashcards
Skin disease is divided into _______
growths and rashes
a neoplastic change in the skin
growth
an inflammatory reaction in the skin
rash
what are growths divided into
epidermal, pigmented, and dermal proliferative processes
Rashes are divided into
with and those without an epidermal component
major function is to act as a barrier against an inhospitable environment- to protect the body from the influences of the outside worth
skin
the major barrier of the skin is
epidermis
contains blood vessels, nerves, and appandeages
dermis
the third deepest layer of the skin is the
subcutaneous fat
what is the principal cell in the epidermis
keratinocytes
what are the layers of the epidermis is ascending order
basal cell
stratum spinosum
stratum granulosum
stratum corneum
undifferentiated , proliferating cells
basal cells
contins keratinocytes connected by desmosomes
stratum spinosum
what kind of granules are seen in seen in the stratum granulosum
keratohyalin granules
major physical barrier of the epidermis
stratum corneum
what determines skin color
number and size of melanosomes, not melanocytes
derived from bone marrow and are the skins first line of immunologic defense
langerhans cells
substrate for attachment of the epidermis to the dermis
basement membrane zone
what are the four major ultrastructural regions of the epidermis
- hemidesmosomal plaque of the basal keratinocyte
- lamina lucida
- lamina densa
- anchoring fibrils located in the sub lamina dense region of the papillary dermis
T/F In normal skin, cell division does not take place above the basal cell layer.
true
How long does it take for cells to be shed?
4 weeks…2 weeks = from basal to granular & 2 weeks = cells to cross the stratum corneum
_____ and _____ increases the rate of proliferation and maturation
injury and inflammation
what differentiate from the basal cells and produce keratin?
keratinocytes
where are keratinocytes located?
stratum spinosum
fibrous protein that is a major component of the horny stratum corneum
keratin produced from keratinocytes
where does the stratum spinosum derive its name from?
spines or intercellular bridges that extend between keratinocytes and are visible with light microscopy
Ultrastructurally what are the “spines” or intercellular bridges in the stratum spinosum composed of?
desmosomes
extensions of keratin within the keratinocyte, functionally they hold cells together
desmosomes
an autoimmune disorder characterized by thickened epidermis and increased scale? associated with what cell layer?
psoriasis- basal cell layer
autoimmune blistering disease wherein antibodies directed against desmosomes result in keratinocyte separation?.
pemphigus vulgaris - stratum spinosum
where do cells acquire additional keratin and become more flattened
stratum granulosum
also in the stratum granulosum cells contain distinctive dark granules, seen easily on light microscopy composed of __________
keratohyalin
What two proteins does keratohyalin contain?
profilaggrin and involucrin
precursor to filaggrin
profilaggrin
plays an important role in the aggregation of keratin filaments int he stratum corneum
profilaggrin
plays a role in formation of the cell envelope of cells in the stratum corneum
involucrin
an inherited dry skin condition secondary to deficient filaggrin production
Ichthyosis vulgaris (as noted on light microscopy of a skin biopsy by a reduced or absent granular layer of epidermis
granular cells also contain ______, which are visualized with electron microscopy.
lamellar granules
contains polysaccharides, glycoproteins, and lipids that extrude into the intercellular space and ultimately are thought to help form the cement that holds together the stratum corneum cells
lamellar granules
responsible for the eventual destruction of cell nuclei and intracytoplasmic organelles - stratum granulosum
degradative enzymes
____ cells contain keratohyalin and lamellar granules
granular cells
latter containing cells that are large, flat, polyhedral, platelike envelopes filled with keratin
stratum corneum
a semi-impenetrable layer that constitutes the major physical barrier of the skin
stratum corneum
dendritic pigment producing cells located in the basal cell layer
melanocytes
the dendrites of melanocytes extend into where? to serve as what?
extend into the stratum spinosum - and serve as conduits
conduits
pigment granules are transferred to their neighboring keratinocytes
The pigment granules are termed ______
melanosomes
pigment within the granules is termed
melanin
what are preferentially situated above the nucleus to protect the DNA
melanosomes
what stimulates the melanocytes to increase pigment production and disperse their melanosomes more widely
sunlight
melanosomes in _________ are larger in size and more numerous compared with melanosomes in ________.
dark skin compared to light skin
the difference in skin pigmentation depends on what?
- number and size of melanosomes
2. dispersion in the skin
dendritic cells in the epidermis that have an immunologic function; derived from bone marrow and constitute about 5% of the cells within the epidermis
langerhan cells
tennis racket shaped granules in stratum spinosum
langerhan cells
identical to tissue macrophages and present antigens to lymphocytes, with which they interact through specific surface receptors.
langerhan cells
located in the basal cell layer, more numerous on the palms and soles and are connected to keratinocytes
merkel cells
function as mechanoreceptors
merkel cells
a rare skin cancer high mortality rate associated with merkel cells
merkel cell carcinoma
what is the dermal epidermal junction - interface between the epidermis and dermis
basement membrane zone
provides structural integrity and is biologically active
dermis
what are the primary components of dermis
collagen, elastin, and extrafibrillar matrix
principal component of the dermis and represents 70% of skins dry weight
collagen
the two fibrous proteins in the dermis that form the strong, yet compliant skeletal matrix
collagen and elastin
what is the uppermost part of the upper dermis
papillary dermis
collagen fibers are fine and loosely arranged in what part of the dermis
uppermost part (papillary dermis)
collagen fibers are thick and densely packed where in the dermis?
reticular dermis
where are elastin fibers primarily located; they are thinner and more loosely arranged than collagen fibers
reticular dermis
what fills the space between fibers
extrafibrillar matrix
a nonfibrous material made up of several several different mucopolysaccaride molecules? collectively called _____ & _____
extrafibrillar matrix
- proteoglycans
- glycosaminoglycans
what imparts to the dermis a more liquid quality which facilities movement of fluids, molecules, and inflammatory cells
extrafibrillar matrix
What are the most important sensory receptors of the skin and where are they found?
Free nerve endings, in the dermis; nerve supply of the skin is segments (dermatomal) with considerable over lab between segments.
What two functions do blood supply of the skin serve? Where are the blood vessels found?
in the dermis
- nutrition
- temp regulation
What does the epidermis depend on for nutrients and oxygen? Why?
Epidermis has no intrinsic blood supply and therefore depends on the diffusion of nutrients and oxygen from vessels in the papillary dermis.
What is the vasculature of the skin arranged in?
Two horizontal plexuses.
- Superficial
- Deep
Located at the lower border of the papillary dermis
superficial vascular plexus
located in the reticular dermis
deep plexus
What is achieved through shunts between the plexuses of the skin? How?
Temperature Regulation
Heat Loss = increased blood flow in the superficial plexus
Heat Gain = shunting of blood to the deep plexus conserves heat
The skin appendages are derived from where?
Epidermis, but except for the nails are located in the dermis
What are the skin appendages
- Eccrine & Apocrine sweat glands
- Hair follicles
- Sebaceous glands
- nails
How are Eccrine glands activated?
emotional and thermal stimuli
What can be used to treat axillary hyperhidrosis by blocking acetylcholine action?
Botox - Botulinum toxin type A
What is the function of the Eccrine sweat gland?
thermal regulation
What is the total secretory capacity of Eccrine sweat glands per day?
10L
Eccrine Sweat secreted in the glandular portion is _____ to plasma but becomes _____ by the time it exits the skin as a result of ductal reabsorption of electrolytes.
isotonic; hypotonic
***glandular excretion is followed by ductal absorption
The eccrine sweat glands are physiologically the most important skin appendage to who?
- physically active individuals
2. ppl living in hot climates
Appocrine sweat glands are ______ dependent. They serve no useful function.
androgen
What are apocrine glands responsible for? How?
Body Odor - action of bacteria on excrete apocrine sweat
Unlike in eccrine glands, in which the secretory cells remain intact, in apocrine glands, the secretory cells _____ their luminal (apical) portions as part of the secretory product.
decapitate
Where is the sweat from the apocrine gland drained into?
hair follice
What are the two sizes of hair?
vellus hairs - short, fine, light colored & barely noticed
terminal hairs - thicker, longer, and darker than the vellus type
How are terminil hairs influenced?
homones - appear at puberty
T/F The cells in the hair bulb replicate faster than the normal epidermal basal cells; these cells constitute the cell matrix.
true
What in the matrix contributes pigment?
melanocytes
As the matrix cells continue to divide what happens to the hair?
it is pushed outward and exits through the epidermis at a rate of about 1 cm per month.
Hair growth in an individual follicle is cyclic, which growth in what phases?
anagen
catagen - transitional
telogen - resting
How much hair is shed per day? How is this normal shedding rate kept constant?
25-100 hairs per day - because at any time 80-90% of scalp hair is in the anagen phase and 10-20% is in the telogen phase
How is the hair sitting in the dermis at rest? What causes it to change?
at an angle; when the arrector pili muscle contracts the hair is in vertical position
What do sebaceous glands produce?
oily substance- sebum
*which has no known function ; in fact the skin of children and the palms and plantar skin of adults function well without sebum.
Where are sebaceous glands found?
where ever hair follicles are found
Ectopic sebaceous glands are often found on mucous membranes where they may form small yellow papules called what?
Fordyce spots
Sebaceous glands are under what type of control?
androgen
When are sebaceous glands enlarged?
New borns - b/c of maternal hormones
preadolescence - stimulation by adrenal androgens to reach full size puberty, when gonadal androgens are produced
What in sebaceous glands are wholly secreted to form sebum. (halocrine secretion)
Lipid-Laden Cells
The majority of the lipid found in sebaceous gland cells is composed of what?
Triglycerides
made of keratin, which is formed from a matrix of dividing epidermal cells; hard and flat and lie parallel to the skin surface
nails
hard translucent structure composed of keratin; ranges in thickness from 0.2 to 0.65
nail plate
what epithelial zone of the nail helps to protect the matrix? how?
proximal nail fold - the stratum corneum produced there forms the cuticle
what epithelial zone of the nail produces the nail plate from its rapidly dividing, keratinizing cells?
matrix
what epithelial zone of the nail produces a minimal amount of keratin which becomes tightly adherent to the bottom of the nail plate?
nail bed
what causes the pink color of the nail?
the vascularity in the dermis of the nail bed
what epithelial zone of the nail underlies the free distal edge of the nail plate.
hyponychium
what seals the junction of the distal nail bed and nail plate?
stratum corneum produced “there” ? forms a cuticle to seal the junction of the distal nail bed and plate.
What lies between the dermis and the underlying fascia?
subcutaneous fat
what is the function of the subcutaneous fat?
- helps to insulate the body from cold
- cushions deep tissues from blunt trauma
- serves as a reserve source of energy for the body
aggregates of fat cells called ______, are separated by fibrous septa that are traversed by blood vessels and nerves where?
subcutaneous fat layer
Biologically active fat cells play a role in _______ as evidence by metabolic disturbances in obese children and adolescents with peripheral insulin resistance.
hormone messaging
