Ex3 L10 - Integument Flashcards
What are the layers of the skin and what composes each layer?
epidermis - epithelial tissue
dermis - connective tissue, hair follicles and sweat glands
hypodermis - adipose tissue
Describe the composition of the epidermis
- keratinized stratified squamous epithelium
- avascular
- keratinocytes that produce keratin
- epidermal stem cells in the stratum basale
- melanocytes that produce melanin
What does keratin do?
toughens and waterproofs the skin
some telomerase activity
Epidermal stem cells in the stratum basale have…
high telomerase activity
What does melanin do?
protect from UV exposure, involved in skin color
What do Langerhans cells do?
immune cells for the epidermis
What do Merkel cells do?
touch receptors for the epidermis
Describe the composition of the dermis
- connective tissue (collagen and elastin)
- rich vasculature (providing nutrients to epidermis)
- few cells, mostly ECM
- dermal-epidermal junction (DEJ)
What is the function of the dermal-epidermal junction (DEJ)
- anchor epidermis to the dermis
- interface for nutrient exchange and signaling between layers
What happens to the dermal-epidermal junction (DEJ) with age?
gets flatter, less surface area for nutrient exchange, contributes to changes with age
What are characteristics of aging skin?
dullness
dryness
thinning
visible pores
increased redness
uneven pigmentation
dark spots
wrinkles
fine lines
tissue ptosis
loss of elasticity
Wrinkles are a result of…
loss of collagen
What is tissue ptosis?
sagging
Changes in aging skin result from…
- modifications to epidermis
- degradation of dermal ECM
- altered dermal-epidermal junction (DEJ)
What is intrinsic aging vs extrinsic aging (of the skin)?
intrinsic - naturally occuring
extrinsic - earlier deterioration from exposure to sunlight (photoaging) or pollution, lifestyle, etc.
How does collagen/wrinkles change with age (due to intrinsic and extrinsic factors)?
young skin - high collagen, no lines or furrows
intrinsic aging only - low collagen, moderate lines and furrows
intrinsic and extrinsic - very low collagen, deep lines and furrows
Dullness of aging skin is a result of…
slower cell turnover rate - as cell turnover rate slows, the cells that remain on the top layer of skin are older and older and therefore are more dull appearing
Describe collagen production/function/change with age
produced: fibroblasts in the dermis
function: structural network for support, tensile strength and firmness
with age: collagenase increases (more degradation) and fibroblast synthesis decreases (less production)
- leads to wrinkles and fragile skin
Describe elastin production/function/change with age
produced: fibroblasts in the dermis
function: stretch and resilience, keep skin pulled tight
with age: develop crosslinks that prevent them from functioning appropriately, become frayed/fragmented, and become thickened and disorganized
- age is also associated with pseudoelastin, which is an intermediate composition of elastic and collagen that is less effective
What are age spots/sun spots?
dysregulated production and processing of melanin
What things contribute to facial appearance and therefore facial aging?
skin, fat, muscle, and bone
- loss of subcutaneous fat and redeposition (under the chin)
- repeated muscle contractions for facial expression lead to wrinkles
Intrinsic aging of the skin occurs at —– rate depending on ——
variable rates
depending on genetic factors and skin type
What stimulates collagenase (other than age)?
cortisol
Skin dryness with age is caused by…
reduced keratin and hyaluronic acid secretion by the fibroblasts of the dermis
With age, skin becomes thinner as…
the dermis and epidermis individually become thinner
What are the main extrinsic factors of skin aging?
- UV light exposure causes photoaging (increases telomerase activity, leading to neoplastic lesions aka skin cancer)
- repeated sun damage can penetrate tot eh dermal layer, especially in thinner aged skin
Sun damage often does not cause problems for young people because…
epidermal cell turnover is fast
What happens to sweat and oil glands with age?
- less sweat production (suderiferous glands)
- less oil production (sebaceous glands) leads to dry flaky skin and brittle hair
What happens to nails with age?
- slowed nail growth
- increased calcium deposition causes yellowing
- disappearance of the lunula
- appearance of longitudinal ridges
Describe the structure of hair
hair is made of dead, keratinized epithelial cells
the hair follicle surrounds the root, and has active telomerase
What is the term for hair graying?
canities
When is hair graying correlated or not correlated with age?
graying of axillary hair - correlated
graying of scalp/facial hair - not always correlated
What are McSCs?
melanocyte stem cells
- give rise to melanocytes
- fail earlier than hair follicle stem cells
- need to move in the hair to function, so if they get stuck the hair becomes gray
- but failed McSCs are not the only cause of gray hair
What are the phases of hair growth?
anagen - growth
catagen - transition
telogen - resting
How do the phases of hair change with age?
in younger age the anagen phase is dominant, but with age the telogen phase lengthens and eventually contributes to hair loss
