- general composition of each layer
-epithelial layer (ectoderm)
-connective tissue (mesoderm)
-projections of dermis into epidermal base
-adjoining epidermal projections that correspond to dermis surface
- take what type of configurations in thin vs. thick skin
purpose -provide structural and morphological integrity between epidermis and dermis (in addition to cellular connections) configuration in thin skin -peg and socket thick skin -ridges and grooves
- type of tissue
- how does it connect to skin?
- underlying tissue covered by…
-deep to dermis
-subcutaneous loose connective tissue
contains adipocytes (fat cells)
not part of skin, but forms loose adhesion of skin to underlying tissue
underlying tissue covered by a fascia plane, which has a variable appearance
skin functions (4)
protection against impact and friction
protection against UV - pigment melanin
thermoregulation, body metabolism and excretion via glands, blood vessels, and adipose
- type of tissues
-stratified squamous keratinized epithelium (named for most superficial strata of epidermis)
-keratinocytes - keratinizing epidermal cells
-langerhans cells - immune system
-merkel cells - sensory receptors?
- dermis + epidermis
epidermis -75-150 um (micrometers) vs. 400-600 um --no explanation of comparison in notes (different areas of the body?) total -up to 4 mm
types of skin
thick (glabrous) -smooth, non-hairy -some books use stratum lucidum as a marker for this type of skin thin -hairy
keratin producing cells (keratinocytes) in epidermis
-names of the layers (5)
stratum basale stratum spinosum stratum granulosum stratum lucidum stratum corneum
- superficial or deep?
- it is basophilic - explain
- single cell layer rests on…
- purpose of desmosomes and hemidesmosomes
- produce filaments called…
- highly mitotic - why?
-abundant in rough ER (endoplasmic reticulum)
-these produce protein
single cell layer rests on basal lamina
desmosomes and hemidesmosomes attach stratum basale to underlying layer
produce filaments called cytokeratins
-partly responsible for constant renewal of overlying layers
stratum spinosum -how many layers -cell shapes -mitotic or not -tonofibrils where is this layer thicker?
more than 1 layer
-variety: cuboidal, polygonal, “slightly” squamous
-tonofilament bundles that attach to the desmosomes interconnecting each cell
-give the spinous appearance in histological preparations
thicker in areas of greater abrasion
- how many layers
- what shape are the cells?
- stains dark due to…
- -what structures are responsible for this process?
3-5 layers polygonal cells stains dark due to... -keratohyalin granules purpose -acts as extracellular cement -purpose achieved due to lamellar granules --lipid-rich product secreted by these cells to "seal" the skin
- more apparent in…
- type of cell
- lacks what function…
- what structures are missing?
- densely packed with…
- what holds the cells together?
more apparent in thick skin appearance -extremely flattened type of cell -eosoniphilic lacks protein synthesis organelles and nuclei are gone densely packed with cytokeratin filaments embedded in matrix desmosomes present to hold cells together
- is there a nucleus?
- filled with…
- -this is embedded in
flattened cells no nuclei 15-20 layers thick filled with protein keratin keratin is embedded in matrix from keratohyalin granules (from stratum granulosum)
other cells found in epidermal layers
- primarily found in which layers?
primarily found in stratum basale and spinosum (2 deepest layers)
neural crest in origin
found in and beneath stratum basale
- how do they accomplish this purpose?
- how does it get moved through the skin?
-encircle the nucleus of the keratinocytes to protect their genetic material from UV radiation
-melanin is packaged into vesicles (through a series of changes that darken and condense) and then extruded and picked up by cells of the malpighian layer
-what does it do to melanin
increases the “darkening” of melanin
speeds up release into the malpighian layer
what is the malpighian layer?
Wikipedia - both the stratum basale and stratum spinosum
- what are they?
bone marrow derived macrophages (mesoderm)
-bind antigens (function with immume system)
within thick skin
-may be sensory due to association with free nerve endings
where are the majority of sensory nerve endings in the skin?
- type of tissue
- -characteristics of each layer
tissue type -connective -dense irregular papillary layer -dermal pegs -lamina reticularis: reticular fibers that contribute to basement membrane reticular layer -dermatan sulfate elastic fiber newtork
- location of blood supply
encapsulated nerve endings
rich blood supply
-deep to epidermis-dermis interdigitation
examples of epithelial invaginations
sebaceous (oil-producing) glands
- when do they begin to function?
- associated pathology
type -acinar (alveolar) glands location -ducted into hair follicle function -produce sebum begin to function at puberty pathology -acne if plugged
- what is it
- how is it secreted?
fat of the gland and remnant of dead secretory cells
-holocrine secretion (whole cell is secreted)
- another name
also called merocrine location -open to skin surface appearance -simple coiled tubular glands watery secretion produced in response to changes in body temperature
- size compared to eccrine glands
- open to…
- responsible for… why?
larger than eccrine
can extend to hypodermis from skin surface
open to hair follicles
responsible for body odor
-secretion is viscous and allows for bacterial decomposition, which leads to odor
- tissue type
- what accumulates there?
type -subcutaneous -loose connective tissue beneath the dermis loosely binds skin to underlying musculoskeletal system adipocytes accumulate there
types of carcinomas
squamous cell carcinoma
basal cell carcinoma
- what is it?
- can turn into…
- also knows as…
precancerous changes to corneal (most superficial) layer of epidermis
may turn into squamous cell carcinoma
also known as Solar keratoses because of…
-prevalence on exposed skin surfaces - arms, face, scalp (in those w/out a nice coif of hair
squamous cell carcinoma
basal cell carcinoma
- how common is it?
- how destructive?
most common type of epidermal cancer
destructive to local tissue
-why is it malignant?
malignant because melanocytes migrate into the epidermal layers
as a result, they will readily leave the local tissue and travel throughout the body and invade all tissues and organs
this makes them a highly metastatic type of cancer
- what predicts the type of epithelial and connective tissue response?
- stages of cutaneous wound healing
thickness of wound predicts response stages -immediate or hemostasis -inflammation -proliferation -maturation