Skin, Hair, Nails Lecture Flashcards
Thermoregulation
Vasoconstriction or vasodilation
Protection
From trauma, chemicals and infections
Prevent dehydration
Synthesis and storage of nutirents
Synthesis of Vit D3 and storage of fat
Sensation
Touch, pressure, pain and temperature
Excretion and secretion
Excretes salts, water, organic waste
Secretes milk to nourish neonates
Function of the skin?
Thermoregulation Protection Synthesis and storage of nutrients Sensation Excretion and secretion
Epidermis Thick skin
Found in palms, soles
Consists of five layers
Epidermis Thin Skin
Found on the rest of the body 4 layers (minus S. Lucidum)
Layers of the Epidermis
Stratum germinativum Stratum spinosum Stratum granulosum Stratum lucidum Stratum corneum
S. germinativum
Deepest layer containg large stem cells (new cell generation)
Forms epidermal ridges that increase nutrient diffusion (form fingerprints)
Contain melanocytes and nerve receptors (touch)
S. Spinosum
Originate from cells of the S. germinativum
Increases the thickness of the epidermis
S. Granulosum
Cells from the S. Spinosum layers
Division stops and Keratin is created
S. Lucidum
Clear layer covering S. granulosum in THICK SKIN of the palms and soles
Cells are flattened and densely packed and filled with keratin
S. corneum
Most superficial layer (15-30 layers of flattened and dead epithelial cells with large amounts of keratin)
Dead cells are connected by desmosomes
Primary barrier to drug entry
- Flakes and dries out
Keratinocyte
New skin cell
Takes 2-4 weeks to move from S. Germinativum to S. Corneum
- Dead cells stay for 2 weeks before shedding out of the S. Corneum
Desmosomes
Hold together keratinocytes
When it degenerates they will flake off
Keratin + Epidermal Homeostasis
Lifeless proteins found in hair, nails and skins,
- Expressed in pairs, Type 1 (acidic) paired with Type II keratin molecule (basic)
Keratinocytes produce
IL-1a, IL-6, and IL-8
Responsive to Vitamin A and D3 –> homeostasis and wound healing
Melanocytes
Produce and contain melanin
Melanin
Pigment manufactured and stored in the cells of the S. germinativum and S. spinosum layers of the epidermis
- Adds color
- Production of melanin is determined by genetics and exposure to sunlight
Langerhans cells
“Immature dendritic cells)
- S. Spinosum
Pick up and process microbial antigens –> migrate to the T cells area and mature to professional APCs
Secrete chemokines and produce adhesions molecules to attract and bind naive T cells
Present to MHC II and CD4s
TH1 vs TH2
1: innate
2: adaptive
Dermis layers?
Papillary layer (upper) Reticular layer (lower)
Papillary layer
Loose connective tissue
Contains capillaries and nerves (pain/touch)
Reticular layer
Collagen and elastic fibers
Rich in vessels and nerves
Areas project downward close to sweat and sebaceous glands and near to hair follicles
Sweat glands
Originate in the dermis and rise through the epidermis to the skin surface
Controlled by SNS
Nerve fiber = sympathetic and neurotransmitter = ACh
Eccrine Sweat Gland
Regulate temperature and waste excretion
Duct opens directly to epithelial surface
Skin of palms, soles, and foreheads
Apocrine Sweat Gland
Scent
Axillae, perineum
Ducts opens to hair shaft
Sebaceous glands
Branched areolar glands located over the surface of the skin (except in palms, soles, and feet)
- Open to hair follicles mainly except in lips and mammary (directly to skin surface)
Function of sebaceous glands
Secrete sebum (sensitive to sex hormone changes)
- Prevent hair from becoming brittle, moisturizes skins and prevents dehydration, has a bactericidal actions
- – excess = acne
Hypodermis
Below the dermis
Composed of adipose and areolar tissue
Function: store fat, insulate, adsorb shock
Classification of hair
Vellus (small, fine, nonpigmented)
Lanugo (fine fetal hair)
Terminal (large mature hair)
Functions of hair
Protection from injury and abrasion
Sensory functions (dogs)
Insulation or temperature regulation
Hair Follicles
Contain capillaries and nerve ending Papilla contain melanocytes (hair color) Along hair shaft: epidermis Around follicle: dermis - As cells divide, the daughter cells are pushed towards the surface to keratinize and die
Age + hair color?
Decreased melanin
Presence of air bubbles in hair shaft
– Hair color lightens
Hair growth
Anagen, Catagen, & Telogen
10-20 cycles during life
When resting phase is complete, the hair follicle converts to anagen phase, and the new anagen hair pushes out the telogen hair after 2-4 months
Anagen
Active hair growth
85-90% of scalp hair (4-8 years)
Catagen
Degeneration
1%
Telogen
Resting
10-15%
Hair loss
Lose about 50 hairs a day
Causes of hair loss
Drug, dietary factors, radiation, high fever, stress, genetics, hormonal factors
Androgenetic alopecia
Female pattern baldness or male pattern baldness
Combined hormonal and genetic issues
- Inherited
- Varying levels of T and DHT (large terminal hair in tiny vellus follicles)
- Treatment: prevention
Minoxidil (Rogaine)
MOA: activation of ATP-dependent K+ channels with enhanced K+ efflux and hyper polarization of cells –> relaxation of arteriolar smooth muscles and decreases blood pressure; not understood for alopecia –> enhances follicular size and prolongs anagen phase
- End treatment = hair loss
- Systemic absorption occurs = cardiovascular symptoms
Finasteride (Propecia)
MOA: inhibition of the enzyme 5-alpha-reductase –> Less T to DHT
MEN only
Increases hair counts
- End treatment = hair loss
- Sexual dysfunction (decreased libido, erectile dysfunction, ejaculation disorder)
Nail function
Protection, tools, weapons
Consist of hard plates of tightly packed keratinized cells
Nail structure
Nail plate: hard translucent, formed compacted layer of S. Corneum
Nail bed: highly vascularized consits of S. Germinativum and S. Spinosum
Nail root: site of nail growth
Toe nails grow less than fingernails
Consideration for topical therapy
Regional anatomic variation
Drug metabolism
Altered or hydrated barrier function (damage S. Corneum, denuded or inflamed skin and hydration - increased absorption)
Vehicle (alter drug absorption)
Age (children > adults and higher skin permeability is increased in preterm infants)
