Skin Flashcards
What % of body weight is skin
12-15%
What does skin protect us from
Physical trauma Infection Penetration of drugs/ chemicals UV Water loss
What are functions of skin, excluding protection
Insulation
Sensory info
Vit. D synthesis
What are the 2 main layers of the skin
Epidermis
Dermis
What type of epithelium is found in the epidermis
Stratified squamous
What is the major cell type of the epidermis
Keratinocyte
Four main layers of epidermis (bottom to top)
Stratum basale
Stratum spinosum
Stratum granulosum
Stratum corneum
What do keratinocytes produce
Keratin
What is the most abundant protein in stratum corneum, hair and nails
Keratin
What are the 2 types of keratin and what makes them different
Soft, alpha type
Hard, beta type
Defined by secondary structure and S-S bonding
The expression pattern of keratins is specific to what
Epidermal layer
Where in the skin does proliferation occur
Basal layer
What maintains epidermis
Population of adult stem cells
Describe the characteristics of adult stem cells found in the epidermis
Long lived, slow cycling
Capable of self-renewal and terminal differentiation
What is the role of the basement membrane
Cell polarity
Regulating basal cell function
Anchoring epidermis to dermis
What does the basement membrane consist of
Laminin 332
Collagen IV
Collagen VII
What are hemidesmosomes
integrin receptors that link the keratin cytoskeleton to the basement membrane
How many cells thick is the stratum spinosum
3-4 cells thick
What gives the stratum spinosum its spiny appearance
Desmosomes
How many cells thick is the stratum granulosum
2-3 cells thick
What characterises stratum granulosum
Keratohyalin
Name 3 types of keratohyalin
- Filaggrin
- Involucrin
- Loricrin
Which layer of skin is the main protective barrier
Stratum corneum
Describe the structure/ features of stratum corneum
Thick cornified envelope
Cross linked by enzymes
What is the role of intercellular lipids in stratum corneum
Maintain moisture
Are cells in stratum corneum dead or alive
Dead
Name 4 cell-cell adhesions seen in skin
- Adherens junctions
- Desmosome
- Tight junction
- Gap junction
What is an adherens junction
Cadherin receptor linked to actin cytoskeleton
What is a desmosome
Cadherin receptor linked to keratin cytoskeleton
What is a tight junction
Claudin and occludin seal intercellular space
What is a gap junction
INtercellular pore made up on connexins
What are the 3 layers of the dermis
Papillary
Reticular
Adipose
Function of the dermis
Provide strength and elasticity to skin
Is dermis vascular and innervated
Yes
What is the most abundant cell in the dermis
Fibroblast
Where does fibroblast originate
Mesenchyme
What do fibroblasts synthesise
Collagen
Elastin
Proteoglycans
Where is the papillary located
Beneath epidermis and BM
What makes up the papillary
Fine, randomly orientated type 3 collagen and elastin
Also contains many blood capillaries
Describe the structure of reticular
Large and densely packed collagen fibre
What layer of the skin provides much of the muscular strength
Reticular
What makes up a pilosebaceous unit
Hair follicle and sebaceous gland
Name the 2 types of hair follicle
Vellus body hair
Terminal scalp/ secondary sexual hair
What produces hair
Matrix keratinocytes
What controls hair growth
Dermal papilla fibroblasts
What do HF stem cells express
Keratin 15
When do HF stem cells given rise to hair cells
Under normal conditions
How do HF stem cells act upon wounding
Contribute to SG and epidemis
What are the 3 phases of the hair cycle
- Anagen-active
- Catagen-regressive
- Telogen- resting
What kind of gland is a sebaceous gland
Exocrine
When does sebaceous gland enlarge and why
Puberty because androgen sensitive
What do mature sebocytes contain
Sebum
How is sebum released
Cell ruptures
Sebum released into duct and onto skin
What causes acne
Sebaceous gland infection
What is the role of eccrine sweat glands
Thermoregulation
What % of sweat is water
99
What are the 2 main components of eccrine sweat gland
Excretory duct
Secretory coil
What is an apocrine gland
Sweat gland associated with hair follicles
What do apocrine secretions smell of
Nothing- odourless
Where are apocrine glands found
Axilla and pubic region
What do apocrine glands release
Volatile fatty acids
Name 4 ‘other’ cell types found in skin
Melanocytes
Langerhans cells
Merkel cell
Mast cell
What kind of cell is a melanocyte
Dendritic cell
What do melanocytes produce
Melanins such as eumelanin and pheomelanin
Where are melanosomes injected into
Keratinocytes
What is the function of melanocytes
Project against UV
In which layers are Langerhan cells found
Basal and spinal
What kind of cell is a Langerhan cell
Dendritic antigen presenting cell
What cell is the first line of defence in skin
Langerhan
What do Langerhan cells do
Present antigens to T lymphocytes
Where are merkel cells found
Stratum basale
What is the function of merkel cells
Sensory perception
Where are mast cells found
Dermis
Function of mast cells?
Immune response- secretes histamine
What skin layers are compromised in a superficial wound
Epidermis
What skin layers are compromised in a partial thickness wound
Epidermis and dermis
What skin layers are compromised in a full thickness wound
Epidermis, dermis, hypodermis
What are the 3 phases of normal wound healing
Inflammation
Proliferation
Maturation
What happens in first 15 mins of inflammation and what cells are involved
Haemostasis
Endothelial cells
What happens between 15 mins- 6 days in inflammation
Erythema, heat, swelling and pain due to endothelial cells, mast cells, neutrophils, macrophages and T lymphocytes
Name 3 complications of wound healing
Infection
Chronic wounds
Scarring
What is the definition of a chronic wound
Not healed after 6 weeks
3 examples of chronic wounds
venous
pressure
diabetic ulcer
