Lecture 2 anatomy of the skin part 2 Flashcards
Summarise the epidermis, dermis and hypodermis
Epidermis….
Stratified barrier
Mostly keratinocytes (skin cells that have heaps of the keratin protein which helps to protect the skin)
No circulation (avascular)
Dermis….
Protein fibres present for strength - elastin and collagen
Vascular (nourishes the epidermis)
Not shed - if a cell dies in the dermis, it gets broken down through the vasculature just like any other cell in the internal part of our body
Hypodermis …..
Contains adipose tissue - insulation and also important for storing energy
Subcutaneous
If you cut the epidermis what would happen?
Can have a superficial graze that won’t have any bleeding since it is avascular
What would happen if you cut the dermis?
Vascular therefore bleeding can occur
Explain the papillary layer
Part of the dermis
Made up of little protrusions and capillaries that sit right under it that provides nourishment to the dermis and the epidermis
Projects into the epidermis
Explain the reticular layer
Part of the dermis
Made up of elastin and collagen that form a mesh for strength (mesh/mat-like structure)
Accessory structures of the skin - hair
Located all over the body (only prominent on the head) (except palms of hands and soles of feet)
It consists of hair shaft (grows from the hair follicle), hair follicle, arrestor pili muscle, sebaceous gland
Accessory structures of the skin - acne
Blockage of hair follicles + infection
Increased sebum increases acne risk - more sebum produced as hormones change around in puberty
Arrector pili muscle
Muscle that causes hair to stand on end. When the muscle contracts it causes the hair to become more upright
Sebaceous glands in hair
Produces sebum which is a natural moisturiser/water repellent
Most of these glands are on the upper part of the body (back, shoulders etc.) - extra oily coat protects homonins when it is raining
Sebum is secreted out on to the shaft of the hair and it helps to nourish and protect the hair and in doing so it makes its way out of the surrounding skin
Lanolin = sheep sebum is used in skincare
Sweat glands - 2 types
Eccrine and apocrine
Eccrine sweat gland
Everywhere and are involved in thermoregulation
Base of them is located in the dermis and the pore is at the skin surface
Apocrine sweat gland
Specialised
Found on the nipples, armpits etc.
Located much deeper on the skin, in the deeper layers of the dermis or hypodermis and rather than terminating at the surface it releases its contents into the hair follicles.
They produce oily sweat rather than salty
Receptors
Nervous tissue
Receptors work based on deformation
Tactile (detect fine changes, superficial) , lamellar (deep, detect pressure), bulbous
Nails
Protect finger tips - more strength/structure at the ends of our fingers
Enhance sensation - sensory receptors require deformation
Melanocytes and melanosomes (skin pigmentation)
The melanin pigment absorbs UV light - protecting cells from UV damage
Produced in melanocytes (i.e. cells). These are the cells that cause skin to be pigmented.
Transferred to epidermal cells by melanosomes - vesicles containing melanin. Melanosomes transport and distribute melanin to various parts of the body therefore one melanocyte can cover a much larger area.
The outer layers of skin are already dead so they can absorb UV light before it even gets to the living cells.
Pigmentation
Protection from UV radiation (high pigmentation)
Vitamin D production ( low pigmentation)
Skin pigmentation is primarily a trait of epithelial cells, in which most of the epidermal melanin resides after being synthesized and transferred from melanocytes.
What does melanin do?
The melanin pigment absorbs UV light, and this protects cells from UV damage
Melanin is produced by cells called melanocytes. It provides some protection again skin damage from the sun, and the melanocytes increase their production of melanin in response to sun exposure. Freckles, which occur in people of all races, are small, concentrated areas of increased melanin production.
Mole
Cluster of melanocytes/local proliferation of melanocytes
Over-proliferation can be caused by sun exposure
Freckle
Melanocytes overproducing melanosomes
Overproduction triggered by sun exposure
Epidermal pigmentation - melanocytes and melanosomes
Melanocytes are only found in the stratum basale - (not shed). We all roughly have the same amount of melanocytes, it is the melanosomes that really determine pigmentation
Melanosomes are found throughout the epidermis (shed with the keratinocytes). More pigmented people have more melanosome production.
Density of melanocytes varies throughout the body but not between races.
Melanocytes are protected by the upper layers.
Why is human skin pigmentation so variable?
Dependent on melanosome production
Skin pigmentation matches __ _______ (in indigenous populations)
UV exposure
More highly pigmented people live around the equator (more sunshine and more UV exposure) and as you move to the poles there is less pigmentation occurring.
Vitamin D generation and rickets
VItamin D is essential for normal calcium metabolism and strong bones - vitamin D deficiency also affects moods
UV exposure in skin is required for vitamin D synthesis
Likely explains the greater incidence of lightly pigmented skin at higher latitudes
When pigmentation does not match UV exposure …
Highly pigmented people are more susceptible to vitamin D deficiency, particularly at extreme latitudes because originally higher numbers around the equator
NZ and skin cancer
NZ has one of the highest rates of skin cancer world-wide.
Reasons…. Large proportion of NZers are pakeha (74%) (i.e. European decent, mostly British - ancestors who lived in a place with much less UV than NZ) AND intense UV in NZ (elliptical orbit of sun, latitude, thin ozone)
Australia is similar
Basal cell carcinoma
Common but relatively benign
Orginates in stratum basale
Metastasis is rare
Malignant melanoma
Rare but deadly if not treated
Orginates in melanocytes (pigmented)
Highly metastatic
Mortality rate is dependent on tumour
How to tell the difference between basal cell carcinoma and malignant melanoma?
Can tell the difference as malignant melanoma has high pigmentation
Thickness of a melanoma highly correlates with ….
Mortality rate
Melanoma depth
Deeper is more dangerous, because closer to the dermis which has the vasculature which allows a route for melanoma cells to transport themselves to a different part of the body and start up a new tumour (metastasis)
Tattoo and skin anatomy
Artificial pigmentation (usually ink) deposited deep within the skin …. Dermal layer which is not shed therefore the ink is captured (but not broken down) inside immune cells/scar tissue (can get pigmentation of lymph nodes)
Pigment is further enough into dermis so that it does not shed
Types of tattoo - trauma, decorative and cosmetic tattoos also there is a Polynesian connection (Maori - ta moko and Samoan - Pe’a)
