Layers & Divisions of the Skin Flashcards
Germinative Layer
- Stratum Germinitavum
- Bottom layer
- Made up of cubical, living cells that are full of fluid and have a nucleus
- Divide through mitosis, producing daughter cells
- Melanocytes produced in this layer
- Vitamin D absorbed in this layer
Malpighian Layer
- Stratum Spinosum
- Extension of germinative layer, both of which make up the basal layer
- The cells are polygonal-shaped, starting to flatten out, and are known as ‘spiny’ or ‘prickle’ cells
- Still contains a nucleus
- Surrounded by fluid
- Connected by fibers
Granular Layer
- Stratum Granulosum
- Cells transforming from fully hydrated cells to dry, waxy flakes
- Nucleus slowly starting to disappear, as it’s losing water and being replaced by keratin (pivotal layer in the skin)
- Keratohyalin granules originate in this layer and activate keratin
- As the cells become keratinized, they move to the surface
Clear Layer
- Stratum Lucidum
- Clear, transparent layer of dead cells just below the skin’s surface
- No nucleus
- Consists of small, transparent cells
- Almost completely dehydrated and invaded by keratin
- Thickest layers = palms of hands & soles of feet
- This layer is responsible for the production of calluses and is found all over the body
Horny Layer
- Stratum Corneum
- Layer that estheticians work on
- Filled with keratin and devoid of fluid
- Firmly cemented together by intercellular cement (thick, waxy coating)
- Acts as a barrier to prevent TEWL
- Approx. 15-20 layers of cells in this layer
- Thickest layer
- In healthy skin, this layer is intact; in sensitive skin, there are holes or tears in this layer (TEWL happening)
Squamous Layer
- Stratum Dysjunctum
- Outermost layer of epidermis, consisting of flat, keratinized cells
- Ready to and will naturally slough off
- Where dull appearance of skin comes from
Three Divisions of the Skin
Epidermis - outer layer made of stratified epithelial tissue
Dermis - intermediate layer made of connective tissue
Hypodermis - inner layer made of adipose connective tissue
Two Divisions of the Dermis
Papillary Layer
Reticular Layer
Dermis
- Inner layer of the skin
- “true” skin - where blood is
- Thickest layer
- Just below epidermis
- Supplies nutrients to epidermis and appendages of skin (hair, nails, and glands)
Papillary Layer
- Makes up 1/5 of the dermis
- Connects the dermis to the epidermis by the dermal-epidermal junction
- Supported by fibroblasts, which are responsible for the production of collagen and elastin
Reticular Layer
- Makes of 4/5 of the dermis
- Denser, deeper layer of the dermis
- Filled with collagen and elastin fibers
- Contains beneficial hydrating fluids like hyaluronic acid
- This layer also has sweat and oil glands, nerves, hair follicles, veins, arteries, lymphatic capillaries, and arrector pili muscle
Hypodermis
- Subcutaneous layer
- Cushions and supports the two layers above it (epidermis and dermis)
- Composed of loose connective tissue and adipose tissue (fat)
- Reduces heat loss through skin
- Decreases with age
Seven Functions of the Skin
- Protection
- Heat regulation
- Absorption
- Secretion
- Excretion
- Respiration
- Sensation
Function of the Skin: Protection
The skin protects the body from four main types of assault:
- Mechanical - pressure, cuts, abrasions, blows, falls (self-healing, shock-absorbing)
- Physical - heat and sunlight radiation
- Chemical - drugs, skin products, pollution, chemicals
- Microbial - bacterial attacks from germs and fungi
Function of the Skin: Heat Regulation
Hypothalamus acts as a thermostat for the body, regulating internal temperature. It signals blood vessels and sweat glands to either increase or decrease blood flow and sweat production to cool our bodies or warm them up.
