20 - Introduction to Skin Flashcards
Most common reason for visiting the GP
Skin disorders
Functions of skin
Protection
Insulation
Sensory information
Vitamin D synthesis
Major cell type of the epidermis
Keratinocytes
What type of cell are in the Epidermis
Stratified Squamous Epithelium
4 layers of the epidermis
Stratum Corneum Stratum Granulosum Stratum Spinosum Stratum Basale (Come Get Sun Burnt)
Function of keratinocyte
Produce keratins
Responsible for cells structural integrity and resillience
Where are keratins most abundant
Stratum corneum
Hair
Nails
A type keratin
More flexible
Soft
In hair
B type keratin
Harder
In nails
More rigid
What defines the two types of keratins
Secondary structure
S-S bonding
What do keratins exist as
Acid-basic pairs
e.g K5/K14
In what layer does proliferation occur in the epidermis
Basal layer
What does the basal membrane consist of
Laminin 332
Collagen IV
Collagen VII
What do cells attach to in the basal membrane
Laminin 332
What is the function of collagen VII in the basal membrane
Mechanical anchorage to the dermis
Function of hemidesmosomes
Link keratin cytoskeleton to basal membrane
Cells in stratum spinosum
3-4 cells thick
Numerous desmosomes
Cells in stratum granulosum
2-3 cells thick Large granules of keratohyalin Filaggrin Involucrin Loricrin
Function of stratum corneum
Protective barrier
structure of stratum corneum
Thick cornified envelope
Cross linked by enzymes
Adherens junctions
Cadherin receptor linked to actin cytoskeleton
Desmosome
Cadherin receptor linked to keratin cytoskeleton
Tight junctions
Claudin and occludin seal intercellular space
Gap junction
Intercellular pores made up of connexins (allow to transport nutrients from one cell to another
Layers of the dermis
Papillary
Reticular
Adipose
Most abundant cell in dermis
Fibroblast
What do fibroblasts synthesise
Collagen
Elastin
Proteoglycans
Papillary layer
Directly beneath the epidermis and BM
Blood capillaries
Why is the papillary layer more elastic
TII collagen and Elastin
Randomly oriented, fine collagen
Reticular layer
Larger, more organised collagen
densely packed
gives skin high tensile strength
What does the pilosebaceous unit comprise of
Hair follicle
Sebaceous gland
What layer of skin is the hair follicle from
Epidermis
Two types of hair
Vellus - body hair
Terminal - Scalp + secondary sexual hair
What produces hair
Matrix keratinocytes
What controls hair growth and where is it
Dermal papilla fibroblasts
IN THE DERMIS
Function of erector pilli muscle
Movement of the hair
Where are hair follicle stem cells located
Bulge region
Express keratin 15
Phases of the hair cycle
Anagen - Active
Catagen - Regressive
Telogen - Resting
What is the sebaceous gland
Androgen sensitive exocrine gland
Releases sebum
Infection –> acne
Components of eccrine sweat gland
Excretory duct
Secretory coil
What is the apocrine gland
Sweat gland associated with hair follicles
Where are apocrine glands found
Axilla
Pubic region
What type of cell are melanocytes
Dendritic cells
Where are melanocytes found
Epidermis on BM and hair matrix
Function of melanocytes
produce melanin in melanosomes
Eumelanin
More common Black or brown
Pheomelanin
Reddish colour
What are langerhans cells
Dendritic cells
presents antigens to t lymphocytes
first line of defence
Where are langerhans found
Basal and spinous layers
Where are Merkel cells found
Stratum basale
Function of merkel cells
Sensory perception
Function of mast cell
Immune response - secretes histamine
Wound healing stages
1) Inflammation
2) Proliferation - active growth and repair
3) Maturation - remodelling
