skin
- layers
- general composition of each layer
epidermis
-epithelial layer (ectoderm)
dermis
-connective tissue (mesoderm)
dermis
-interdigitation properties
dermal papillae
-projections of dermis into epidermal base
epidermal ridges
-adjoining epidermal projections that correspond to dermis surface
interdigitations
- purpose
- 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
hypodermis
- location
- type of tissue
- contains
- how does it connect to skin?
- underlying tissue covered by…
location
-deep to dermis
tissue type
-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)
receptor organ
protection against impact and friction
protection against UV - pigment melanin
thermoregulation, body metabolism and excretion via glands, blood vessels, and adipose
epidermis
- type of tissues
- contains
type
-stratified squamous keratinized epithelium (named for most superficial strata of epidermis)
contains
-keratinocytes - keratinizing epidermal cells
-melanocytes
-langerhans cells - immune system
-merkel cells - sensory receptors?
skin thickness
- epidermis
- 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
-characteristics
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
stratum basale
- superficial or deep?
- it is basophilic - explain
- single cell layer rests on…
- purpose of desmosomes and hemidesmosomes
- produce filaments called…
- highly mitotic - why?
deepest layer
basophilic
-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
high mitotic
-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
shapes
-variety: cuboidal, polygonal, “slightly” squamous
mitotic
tonofibrils
-tonofilament bundles that attach to the desmosomes interconnecting each cell
-give the spinous appearance in histological preparations
thicker in areas of greater abrasion
stratum granulosum
- how many layers
- what shape are the cells?
- stains dark due to…
- purpose
- -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
stratum lucidum
- more apparent in…
- appearance
- 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
stratum corneum
- appearance
- is there a nucleus?
- thickness
- 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
- names
- primarily found in which layers?
melanocytes
langerhans cells
merkel’s cells
primarily found in stratum basale and spinosum (2 deepest layers)
melanocytes
- origin
- location
- function
neural crest in origin
found in and beneath stratum basale
produce melanin
melanin
- purpose
- how do they accomplish this purpose?
- how does it get moved through the skin?
purpose
-encircle the nucleus of the keratinocytes to protect their genetic material from UV radiation
movement
-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
sun tan
-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
langerhans cells
- what are they?
- purpose
bone marrow derived macrophages (mesoderm)
purpose
-bind antigens (function with immume system)
Merkel’s cells
- location
- purpose
within thick skin
purpose
-may be sensory due to association with free nerve endings
where are the majority of sensory nerve endings in the skin?
dermal layer
dermis
- type of tissue
- layers
- -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
dermis
- characteristics
- location of blood supply
encapsulated nerve endings
epithelial invaginations
rich blood supply
-deep to epidermis-dermis interdigitation
examples of epithelial invaginations
hair
sweat glands
sebaceous (oil-producing) glands
sebaceous glands
- type
- location
- function
- 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
sebum
- what is it
- how is it secreted?
fat of the gland and remnant of dead secretory cells
secretion
-holocrine secretion (whole cell is secreted)
sweat glands
-types
eccrine
apocrine
eccrine
- another name
- location
- appearance
- function
also called merocrine location -open to skin surface appearance -simple coiled tubular glands watery secretion produced in response to changes in body temperature
apocrine
- size compared to eccrine glands
- location
- 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
hypodermis
- tissue type
- location
- function
- what accumulates there?
type -subcutaneous -loose connective tissue beneath the dermis loosely binds skin to underlying musculoskeletal system adipocytes accumulate there
types of carcinomas
actinic keratosis
squamous cell carcinoma
basal cell carcinoma
malignant melanoma
actinic keratosis
- what is it?
- can turn into…
- also knows as…
- -why
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
-danger level
locally invasive
can metastasize
basal cell carcinoma
- how common is it?
- how destructive?
most common type of epidermal cancer
destructive to local tissue
malignant melanoma
-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
wound healing
- 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
