Skin Flashcards
Functions of skin
Barrier - water loss and entry. Burned can result in dehydration due to loss of barrier
Microorganisms
- physical barrier
- oil of skin is antibacterial (Sebum)
- sweat (slightly acidic - inhibits bacterial growth)
Ultra-violet radiation - melanin
Excretory organ - sweat
Synthesis of Vit D - by action of UV, Ca2+
Sense organ - touch, pressure etc
Layers of skin
Epidermis - keratinocytes
Dermis - layers of connective tissue
Hypodermis - subcutaneous layer
List layers of Epidermis
Stratified squamous epithelium
Has 5 zones
Stratum corneum
Stratum Lucidum
Stratum Granulosum
Stratum Spinosum
Stratum basale
Stratum corneum
dead cless, lost as skin replaces itself
Stratum lucidum
Only in thick skin
Stratum granulosum
Oils, proteins - waterproof the skin
Stratum spinosum
Structure and strength
Spot desmosomes
Keratin
Stratum basale
Basal layer - stem cells
40 days to migrate from base to be lost
Thick skin
epidermis: 400-600um
Palms of hands including fingers, soles of feet included toes - protection to areas under stress
Increased Stratum corneum
Thin skin
epidermis: 75 to 150 um - rest of body
Keratinocyte
Immune role - produce cytokines
Epithelial cells - gives epidermis strength (structure)
Melanocyte
Produce melanin
Darker skin - more active melanocytes
Langerhans cells
Dendritic cells - detect foreign bodies -> immune response
Keratin
Key structural material
Forms intermediate filaments giving strength, protection and waterproofing for skin.
Keratin of hair and nails more tightly packed
Melanin
Production occurs afters exposure to UV radiation, causing skin to tna
Released by melanocytes and taken up by keratinocytes
Darker skin is due to more active melanocytes, not a great number
Attachment of epidermis to dermis
Epidermis attached by epidermal ridges
Contour of skin follows these ridges - leads to formation of structures like finger prints
Layers of dermis
Papillary layer - areolar connective tissue
Reticular layer - dense irregular connective tissue. Bundles of collagen arranged in different orientations. Strength allows movement in different directions
Papillary layer
Consists of loose connective tissue, blood vessels, cells and sensory receptors.
Allows movement of immune cells to detect bacteria
Dermal papillae - blood vessels nourish all hair follicles, bring nutrients and oxygen to the lower epidermal cell layers
Reticular layer
Dense, irregular collagen I that surrounds hair follicles, blood vessels and glands.
Contains majority of elastin in dermis
Fibroblasts
Produce collagen and elastin
Mast cells
Produce cytokines
Collagen in skin
Responsible for skin strength and elasticity. Its degradation leaks to wrinkles that accompany aging
Elastin
Allows skin to return to its original position after stretching or contracting
- aging leads to loss of elastin fibres
Hypodermis
Loose connective tissue and adipocytes
Bind skin to underlying tissues, provides padding and thermal insulation
Skin derivatives
Nails, hair, sebaceous and sweat glands
Nails
Nail body is formed from nail matrix
Hair
Hair is produced from hair matrix and hair papilla inside the hair bulb have blood vessels that nourish the hair
Sebaceous glands
Oily substance called sebum
Holocrine secretion - cells break down
Sweat gland
Apocrine swell gland found in axillae, groin and nipples. Produce apocrine sweat -> bacteria and body odor. Loss of part of cell but is replaced
Merocrine sweat glands replace via blebs from the membrane and cool the body as sweat evaporates.
Skin as a sensory organ
Has thermoreceptors (heat), nociceptors (pain) and mechanoreceptors.
Thermoregulation
TRP receptors
Primary sensory cortex receives conscious response to temperature
Hypothalamus receives autonomic response to temperature
Cold thermoreceptors
TRPA1, TRPM8, TRPC5
Innocuous thermoreceptors
TRPV4, TRPM2 TRPV3
Hot thermoreceptors
TRPV1 (chilli), TRPM3, TRPV2
Cold ligands
Eucalyptol, Menthol, Ilicin
Warm ligands
Camphor, Carvacrol, Eugenol, thymol
