Anatomy of the Skin - Part 2 Flashcards
What are the accessory structures of the skin?
Hair, sweat glands, nails, receptors
Describe the accessory structure - hair
- Found everywhere except for where there is thick skin
- Made of dead, keratinised cells produced inside hair folicle
- Hair shaft projects from the follicle
Describe the features of the accessory structure hair
Arrector pili muscle:
- contraction produces ‘goosebumps’, Improves insulation by trapping air inside the pore.
- is a type of muscular tissue
Root hair plexus:
- collection of sensory nerves at the base of each hair follicle. heightened sensation.
Sebaceous glands:
- produce oily secretion called sebum
- nourishes hair shaft and naturally moisturises the skin
- water repellent
- blocked hair follicles + infection due to increased sebum production leads to acne
Lanolin:
- sheep sebum. purified and used commercially in skin care products
Describe the functions of the two types of accessory structure - sweat glands
Eccrine:
- found in most areas of the skin
- pour watery secretions directly onto skin surface
- important in thermoregulation and excretion
- some antibacterial action
Apocrine:
- Found in specific areas. eg. armpit, groin, and around nipples
- secret sticky/oily and at times potentially odours secretions into the base of the hair follicle
- influenced by hormones
Describe the accessory structures - receptors and nails
Receptors:
- tactile
- lamellar
- bulbous
Nails:
- Protect fingertips/toes (from bending back too much and causing injury)
- 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 deficiency
- Tattoo (artificial pigmentation)
Describe what skin aging is
- Thin epidermis (due to fewer daughter cells being produced and pushing up to the surface, leading to a thinner epidermis)
- Thin dermis (sagging and wrinkling)
- reduced collagen (because it degrades as we age)
- Slower skin repair (due to lower vascularity because its not as efficient to get blood there as when we were younger)
- Drier epidermis (less sebum - also due to low vascularity)
- Impaired cooling (less sweat)
- Less pigmentation
- pale skin, grey hair
Describe how skin aging is impacted by smoking
Tabacco (cigarettes):
- contains agents that accelerate aging
- Damages collagen and elastin in the skin
- linked to poor wound healing, acne, skin and oral cancers
Nicotine (vaping):
- contains nicotine
- nicotine reduces blood circulation in the dermis
- contact dermatitis (skin inflammation) die to metal coating on vapes
Describe skin pigmentation and the cells/pigments involved
- The melanin pigment absorbs UV light - protecting cells from UV damage
- Produced in melanocytes (cells that produce melanin) which are only found in the stratum basali
- Transferred to epidermal cells by melanosomes (vesicles containing melanin - which are found throughout the epidermis)
- The density of melanocytes varies throughout the body and through time
What is the difference between a mole and a freckle?
Mole: Cluster or melanocytes. Over-ploriferation can be caused by sun exposure
Freckle: Melanocytes overproducing melanosomes. Over-production triggered by sun exporsure.
Describe why pigmentation in skin varies across countries and populations
- Skin pigmentation matches sun exposure, so people who live closer to the equator generally have darker skin (more melanin produced) to protect their skin layers against the UV rays. In higher latitudes the skin generally is lighter as there are less UV rays and they need to be able to get enough to make sufficient vitamin D.
What is the importance of Vitamin D?
- Vitamin D is essential for normal calcium metabolism and strong bones.
- Vitamin D deficiency causes rickets
- Vitamin D can also affect mood
- Vitamin D deficiency causes rickets
- UV exposure in skin is required for vitamin D synthesis
- Likely explains the greater incidence of lightly pigmented skin at higher latitudes
What is happening when pigmentation does not match UV exposure?
- Highly pigmented people are more susceptible to Vitamin D deficiency, particularly at extreme latitudes because their high pigmentation blocks the UV.
- The incidence of rickets increased as people started spending more time indoors, and when they were outside they were more sun smart (and therefore didn’t get enough UV when they did go outside.
- The increase of rickets in spring is a result of lack of sun during the winter months, now showing up.
- New Zealand has once of the highest skin cancer rates worldwide because we have less pigmentation and a thinner ozone layer.
Describe basal cell carcinoma vs. malignant melanoma
Basal cell carcinoma (BCC):
- Common but relatively benign (because the cells are only pushed up and generally don’t spread out)
- Originates in stratum basale
- Metastasis (spread) is rare
Malignant melanoma:
- Rare but deadly if not treated (because it spreads deeper into the skin and then eventually into the bloodstream where it travels and then colonises wherever it ends up)
- Originates in melanocytes (pigmented)
- Highly metastatic
- Mortality rate depends upon tumour (how deep it has spread/thickness of it)
Describe tattoos and how they relate to skin anatomy
Artificial pigmentation (usually ink) deposited within the skin
- dermal layer ie. not shed
- captured (but not broken down) inside immune cells/scar tissue which holds the ink in one place so the tattoo doesn’t move
Types of tattoo
- trauma, decorative
- cosmetic tattoos (eg. eyebrows)
Polynesian connection
- Māori, Tā moko
- Samoan, Pe’a
Pain is experienced when getting a tattoo because the dermal layer contains the pain receptors and free nerve endings.
