Lecture Two - Skin Flashcards
Skin accessory structures
- hair
- sweat glands
- receptors
- nails
Where is hair found
All over the body except palms, soles and lips
What is hair made of?
Made of dead, keratinised cells produced inside a hair follicle
- hair shafts projects from the follicle
Accessory structures - hair
- arrector pili muscle
- root hair plexus
- sebaceous glands
What does the arrector pili muscle do?
- contraction produces ‘goose bumps’
- improves insulation
What is the root hair plexus and what does it do?
- a collection of sensory nerves at the base of each hair follicle
- heightened sensation
What do the sebaceous glands do?
- produce oily secretion called sebum
- nourished hair shaft and naturally moisturises skin
- water repellent
- blocked hair follicles + infecutoion due to increase sebum production leads to acne
What does increased sebum production do
- results in blocked hair follicles and infection leading to acne
What is lanolin?
- sheep sebum
- purified and used commercially in skin care products
Where are eccrine sweat glands found?
- found in most areas of the skin
What do eccrine sweat glands do?
- pour watery secretions directly onto the skin surface
- important in thermoregulation and excretion
- some antibacterial action
Where are apocrine sweat glands found?
- found in specific areas
E.g: armpit, groun and around nipples
What do apocrine sweat glands do?
- secrete sticky/oily and at times potentially odorous secretions into the base of the hair follicle
- influences by hormones e.g lactation
Receptors
- tactile
- lamellar
- bulbous
What do nails do?
- protect fingertips / toes
- enhance sensation
- sensory receptors require deformation
How does skin anatomy relate to its function ?
- aging
- pigmentation
- protection from UV radiation (high pigmentation)
- vitamin D production (low pigmentation)
- skin cancer / vitamin D insufficiency
- tattoo (artificial pigmentation)
Skin aging
- thin epidermis
- thin dermis (sagging/wrinkling) - reduced collagen
- slower skin repair
- drier epidermis (less sebum)
- impaired cooling (less sweat)
- less pigmentation (pale skin, grey hair)
Smoking and skin aging - tobacco
- contains agents that accelerate aging
- damages collagen and elastin in the skin
- linked with poor wound healing, acne, skin and oral cancers
Vaping and skin aging
- contains nicotine
- nicotine reduces blood circulation in the dermis
- contact? Dermatitis (skin inflammation) due to metal coating on e-cigarettes
Difference betweeen a mole and a freckle
Mole:
- cluster of melanocytes
- over proliferation can be caused by sun exposure
Freckle:
- melanocytes overproducing melanosomes
- over produciotn triggered by sun exposure
Skin _____ matches ____ exposure
Skin pigmentation matches UV exposure ( in indigenous populations)
Vitamin D is essential for…
- normal calcium metabolism
- strong bones
Vitamin D diffieicny causes …
- rickets
- affects mood
What is required for vitamin D synthesis
- UV exposure in skin
This explains the greater incidence of lightly pigmented skin at higher latitudes
Who is more susceptible to vitamin D dificiency ?
Highly pigmented people are more susceptible to vitamin D deficiency, particularly at extreme latitudes
Why NZ has one of the highest rates of skin cancer world wide… why?
- large European population
- intense UV (elliptical orbit of sun, latitude, thin Ozone)
- Australia is similar
What absorbs UV light? And what does it result in?
Melanin pigment absorbs UV light, protecting cells from UV damage
Where is melanin produced?
In melanocytes (cells)
How is melanin pigment transferred to epidermal cells?
Melanin pigment is transferred to epidermal cells by melanosomes (vesicles containing melanin)
Where are melanocytes found
Melanocytes are only found in the stratum basale - they are not shed
Where are melanosomes found
Melanosomes are found throughout the epidermis - is shed with keratinocytes
Desity of melanocytes ?
Varies throughout the body and through time
Basal cell carcinoma
- common but relatively benign
- originates in stratum basale (gets moved away from blood stream via epidermis shedding)
- metastasis (spread) is rare
Malignant melanoma
- rare but deadly if not treated
- originates in the melanocytes (pigmented)
- highly metastatic
- mortality rate dependent upon tumour
The thickness of melanoma highly correlates with mortality rate
Tattoo and how it relates to skin anatomy
Artificial pigmentation (usually ink) deposited deep within the skin
- dermal layer, i.e - not shed
- captured (but not broken down) inside immune cells/scar tissue
- ‘Lena’ tattoo, pigmentation of lymph nodes
Pigment in lymph nodes =
Tattoo
Not melanoma
Types of tattoo
- trauma
- decorative
- cosmetic tattoos
Tattoo Polynesian connection
- Māori, ta moko
- Samoan, Pe’a
Skin is composed of…
All four basic tissue types:
Epithelial, muscular, nervous and connective
