Skin Flashcards
What is the dead cell skin layer made of?
Keratin which is made of keratinocytes (epidermal cells)
What are the main functions of the skin? (4)
- Protection (against UV light, mechanical, chemical or thermal insults)
- Sensation (largest sensory organ, contains receptors for touch, pressure, pain and temperature)
- Thermoregulation (insulation occurs through piloerection, and subcutaneous adipose tissue and cooling occurs through sweat evaporation or vasodilation)
- Metabolic functions (subcutaneous adipose tissue is a large energy store mainly in the form of TAGs, vitamin D is synthesised in the epidermis
What are the 2 layers of the skin?
- epidermis
- dermis
(and hypodermis/ superficial fascia underneath the layers)
What are the functions of the epidermis? (5)
- epithelium has 5 strata-layers
- confined layer of flat, dead skin cells (stratified squamous keratinising epithelium)
- forms a boundary between internal and external compartments
- mainly composed of keratinocytes (renewing layer of cells)
- prevents water loss by evaporation
What are the functions of the dermis? (7)
- has 2 layers of dense connective tissue
- gives structural strength (reduces risk of external injury)
- contain nerves, glands and blood vessels that supply to the skin
- Maintains the epidermis by its blood flow
- Permits body cooling (e.g. loss of heat by production and evaporation of sweat or dilated blood vessels)
- Immune surveillance
- UV protection
- Energy storage
- contains sensory information
What are the functions of the hypodermis/ superficial fascia?
- adipose/fatty layer beneath the skin
- not part of the skin
- also known as superficial fascia or subcutaneous tissue
- anchors skin to underlying structures
- contains loose connective tissue
What are the 4 main cell types found in the epidermis?
- Keratinocytes (resistance to abrasion, most frequent, waterproof due to extrude lipids, self-regenerating)
- Melanocytes (form skin pigmentation)
- Langerhans cells (immune surveillance)
- Merkel cells (touch receptors)
What are 5 epidermal layers?
- stratum corneum
- stratum lucidum
- stratum granulosum
- stratum spinosum
- stratum basale
COME, LET’S GET SUNBURNT or BRAIN SCAPE, GREAT LEARNING CURVE
What are the properties of stratum basale? (5)
- tall columnar cells with melanocytes and merkel cells
- bound to basal membrane with hemidesmosomes
- continous cell proliferation (stem cells, undifferentiated)
- pilli found on stratum basal strengthen cell network
- irregular interference with dermis
What are the properties of stratum spinosum? (4)
- spinous layer (has spines)
- created post-mortem, cells shrink but desmosome junctions create spines
- little structural evidence of activity
- preparative layer for keratinisation
What are the properties of stratum granulosum? (2)
- presence of granules define the layer
- granules of keratohyalin (possible precursors of keratin
What are the properties of stratum lucidum? (3)
- difficult to distinguish from stratum corneum
- conversion of keratohyalin to keratin
- lots of disulphide bridges give strength
What are the properties of stratum corneum? (3)
- cells have no nuclei or organelles
- desmosomes bind cells
- 15-30 day turnover
What is keratinisation?
Development/ conversion of skin cells into keratin where keratin is deposited in cells forming hair, nails, dead skin cells.
As cells differentiate they move up the epidermal layers (keratinisation) until they become dead keratinocyte cells on the upper level.
What is psoriasis?
Autoimmune disorder whereby excessive keratinisation occurs and leaves keratin deposits on skin (particularly the elbows and knees)
