Lecture 2 anatomy of the skin part 2

Question 1

Summarise the epidermis, dermis and hypodermis

Answer 1

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

Question 2

If you cut the epidermis what would happen?

Answer 2

Can have a superficial graze that won’t have any bleeding since it is avascular

Question 3

What would happen if you cut the dermis?

Answer 3

Vascular therefore bleeding can occur

Question 4

Explain the papillary layer

Answer 4

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

Question 5

Explain the reticular layer

Answer 5

Part of the dermis

Made up of elastin and collagen that form a mesh for strength (mesh/mat-like structure)

Question 6

Accessory structures of the skin - hair

Answer 6

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

Question 7

Accessory structures of the skin - acne

Answer 7

Blockage of hair follicles + infection

Increased sebum increases acne risk - more sebum produced as hormones change around in puberty

Question 8

Arrector pili muscle

Answer 8

Muscle that causes hair to stand on end. When the muscle contracts it causes the hair to become more upright

Question 9

Sebaceous glands in hair

Answer 9

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

Question 10

Sweat glands - 2 types

Answer 10

Eccrine and apocrine

Question 11

Eccrine sweat gland

Answer 11

Everywhere and are involved in thermoregulation

Base of them is located in the dermis and the pore is at the skin surface

Question 12

Apocrine sweat gland

Answer 12

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

Question 13

Receptors

Answer 13

Nervous tissue

Receptors work based on deformation

Tactile (detect fine changes, superficial) , lamellar (deep, detect pressure), bulbous

Question 14

Nails

Answer 14

Protect finger tips - more strength/structure at the ends of our fingers

Enhance sensation - sensory receptors require deformation

Question 15

Melanocytes and melanosomes (skin pigmentation)

Answer 15

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.

Question 16

Pigmentation

Answer 16

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.

Question 17

What does melanin do?

Answer 17

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.

Question 18

Mole

Answer 18

Cluster of melanocytes/local proliferation of melanocytes

Over-proliferation can be caused by sun exposure

Question 19

Freckle

Answer 19

Melanocytes overproducing melanosomes

Overproduction triggered by sun exposure

Question 20

Epidermal pigmentation - melanocytes and melanosomes

Answer 20

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.

Question 21

Why is human skin pigmentation so variable?

Answer 21

Dependent on melanosome production

Question 22

Skin pigmentation matches __ _______ (in indigenous populations)

Answer 22

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.

Question 23

Vitamin D generation and rickets

Answer 23

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

Question 24

When pigmentation does not match UV exposure …

Answer 24

Highly pigmented people are more susceptible to vitamin D deficiency, particularly at extreme latitudes because originally higher numbers around the equator

Question 25

NZ and skin cancer

Answer 25

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

Question 26

Basal cell carcinoma

Answer 26

Common but relatively benign
Orginates in stratum basale
Metastasis is rare

Question 27

Malignant melanoma

Answer 27

Rare but deadly if not treated
Orginates in melanocytes (pigmented)
Highly metastatic
Mortality rate is dependent on tumour

Question 28

How to tell the difference between basal cell carcinoma and malignant melanoma?

Answer 28

Can tell the difference as malignant melanoma has high pigmentation

Question 29

Thickness of a melanoma highly correlates with ….

Answer 29

Mortality rate

Question 30

Melanoma depth

Answer 30

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)

Question 31

Tattoo and skin anatomy

Answer 31

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)