part 1- layers of the skin Flashcards
what is the skin made of
the skin is made of tissues that work together as a single structure to perform unique and critical function
what system does the skin belong to?
the skin is part of the integumentary system
what does the skin and its accessory structures provide the body with?
the skin provides the body with overall protection
how is the skin held to underlying structures
held to underlying structures by connective tissue
what is the characteristic of the deepest layer of the skin?
the deeper layer of the skin is well vascularized (has numerous blood vessels)
what does the skin contain for communication
the skin contains numerous sensory and nerve fibres ensuring communication to and from the brain
what type of epithelium is the epidermis composed of?
the epidermis is composed of keratinized, stratified squamous epithelium
is the epidermis vascular or avascular?
the epidermis is avascular and does not have any blood vessels within it
what is the classification of most skin?
most of the skin is classified as thin skin, which has four visible layers of cells
what are the 4 visible layers of cells in thin skin from deep to superficial?
- stratum basale
- stratum spinosum
- stratum granulosum
- stratum corneum
where is the thick skin found?
thick skin is found only on the palms of the hands and the soles of the feet
what is the fifth layer found in thick skin, and where is it located?
fifth layer is the stratum lucidum, located between the stratum corneum and the stratum granulosum
where is the stratum basal located in the epidermis?
deepest epidermal layer
what does stratum basal attach to?
attaches the epidermis to the basal lamina, which lies above the dermis
what is the function of collagen fibres in the statum basale?
collagen fibres in the stratum basal bond the epidermis to the dermis, forming the basement membrane
what are the dermal papillae?
dermal paillae are finger like projections in the dermis that increase the strength of the connection between the dermis and the epidermis
how do dermal papillae affect the connection between dermis and epidermis?
greater the folding of dermal papillae, the stronger the connection between the dermis and epidermis
what type of cells primarily make up the stratum basale?
primarily made up of basale cells
function of basal cells in the stratum basale?
they are stem cells that give rise to the keratinocytes of the epidermis through mitosis
what happens as new cells are formed in the stratum basale?
as new cells are formed, existing cells are pushed away from the stratum basale to more superficial layers
what are the other two cell types found in the stratum basale?
the other two cell types are Merkel cells and melanocytes
what is the function of Merkel cells in the stratum basale?
Merkel cells function as touch receptors stimulating sensory nerves that the brain perceives as touch
where are Merkel cells especially abundant?
on the surfaces of the hands and feet
function of melanocytes in the stratum basale?
produce the pigment melanin, which gives skin and hair color and protects against UV radiation
when do finger prints in a fetus form?
the cells of the stratum basale meet the papillae of the underlying dermal layer (papillary layer), resulting in the formation of the ridges on your fingers that you recognize as fingerprints.
what gives stratum spinosum its “spiny” appearance?
the protruding cell processes that join cells via desmosomes
why does the “spiny” appearance of the stratum spinosum occur?
its an artifact of the staining process; unstained epidermis does’t show this feature
how many layers of the keratinocytes are found in the stratum spinosum?
8 to 10 layers of k
what type of cell is found in the stratum spinosum and what is it’s function?
langerhans cells, which act as macrophages, engulfing bacteria, foreign particles, and damaged cells
what role do keratinocytes in the stratum spinosum play?
they begin synthesizing keratin and releasing a glycolipid to prevent water loss
how are the keratinocytes of the stratum spinosum moved?
they are pushed into the stratum granulosum as new keratinocytes are formed in the stratum basale
what gives the graunlosum its “grainy” appearance?
the accumulation of keratin and keratohyalin proteins within the cells
how many layers of cells are in the stratum granulosum?
three to five layers of cells
what changes occur to the keratinocytes in the stratum granulosum?
cells become flatter, cell membrane thicken, and they generate large amounts of keratin and keratohyalin
what happens to the nuclei and cell organelles in the stratum granulosum?
they disintegrate as the cells die, leaving behind keratin, keratohyalin and cell membranes
what do the remnants of the cells in the stratum granulosum form?
the stratum lucidum, stratum corneum and accessory strucutes like hair and nails
where is stratum lucidum found?
thick skin such as palms, soles and digits (finger or toe)
what is the appearance of the stratum lucidum?
it is a smooth, translucent layer
what type of cells make up the stratum lucidum?
dead, flattened keratinocytes
what protein do the cells of stratum lucidum contain, and what function?
eleiden, a clear protein driven from keratohylain, which gives the cells their transparent appearance and acts as a water barrier.
what is the stratum corneum?
most superficial layer of the epidermis, exposed to outside environment
why is the stratum corneum named as such?
due to increased keratinization (cornification) of the cells
how many layers of cells are typically in the stratum corneum?
15 to 30 layers of cells
how to remember layers of epidermis dermis and hypodermis
epi= over
hypo= under/below
dermis
It contains blood and lymph vessels, nerves, and other structures, such as hair follicles and sweat glands. The dermis is made of two layers of connective tissue that compose an interconnected mesh of elastin and collagenous fibres, produced by fibroblasts
what type of connective tissue makes up the papillary layer?
loose, areolar connective tissue
what structure forms in the papillary layer and projects into the stratum basale?
dermal papillae (finger like projections)
what cells are found within the papillary layer?
fibroblasts, adipocytes (fat cells) and phagocytes
what is the role of phagocytes in the papillary layer?
help fight bacteria and infections that breach the skin
what additional strucutes are found in the papillary layer?
small blood vessels, lymphatic capillaries, nerve fibres and tactile corpuscles (touch receptors)
what type of connective tissue makes up the reticular layer?
dense, irregular connective tissue
what fibres make up the reticular layer and what do they provide?
elastin fibres (for elasticity) and collagen fibres (for the structure, tensile strength and hydration)
how does collagen in the reticular layer help the skin?
it provides tensile strength, structure and binds water to keep the skin hydrated
how does the reticular layer appear under a microscope?
it appears reticulated (net like) due to the tight meshwork of fibres
what is the main function of the hypodermis?
it connects the skin to the underlying fascia of bones and muscles
what tissues make up the hypodermis?
loose, areolar connective tissue and adipose tissue
what are the functions of adipose tissue in the hypodermis?
fat storage, insulation and cushioning for the integument
what pigments influence skin colour?
melanin, carotene and hemoglobin
what is melanin produced?
my melanocytes in the stratum basale of the epidermis
how is melanin transferred to keratinocytes?
through melanosomes, cellular vesicles that carry melanin
how does sun exposure affect melanin production ?
UV rays stimulate keratinocytes to secrete chemicals that activates melanocytes, increasing to melanin production and resulting in a tan
what is the role of melanin in protecting the skin?
it helps protect the DNA of epidermal cells from UV damage
what is the downside of excessive melanin production?
too much melanin can interfere with vitamin D production, affecting calcium absorption
