HUMAN SKIN : THE GOOD : SKIN PHYSIOLOGY
Professor Lester M. Davids
[[email protected]]
January 2017
HUMAN SKIN
EPIDERMIS
DERMIS
HYPODERMIS
WHAT GIVES OUR SKIN IT’S COLOUR ?
“THE PIGMENT FACTORY”
KERATINOCYTE
MELANOCYTE
BAGS OF MELANIN PIGMENT
SKIN COLOURS
MELANIN PIGMENT =
ALBINISM
VITILIGO
WHY IS THE MELANIN PIGMENT SO IMPORTANT ?...
MELANIN PIGMENT =
11 JANUARY!
UV-B
UV-A
- Cloud cover
UVC
O3
- Ozone in the
stratosphere
O3
O3
O3
- Oblique angle of
sunlight
- Altitude
-Dust and Smoke
O3
O3
O3
Earth
UVC
0%
UVA
UVB
10%
90 %
UVA
UVB
- Wavelength: 320-400 nm
- Least energetic, but harmful, destroys
collagen and elastin
- Passes the earth’s atmosphere
almost unfiltered.
- The amount that reaches the earth’s surface stays
constant through the seasons and time of day.
- Not filtered by glass
- Wavelength 290-320 nm
- Lower energy levels and longer
wavelength than UVC
- Destroys DNA directly!!
- Some gets to the earth’s
surface.
Durban
Cape Town
CAPE TOWN - PROVEN TO HAVE THE HIGHEST UVB
EXPOSURE IN SA
UV-A – “AGEING” WAVELENGTH
UV-B – “BURNING” WAVELENGTH
MED = MINIMAL ERYTHEMAL DOSE
- defined as minimal sun exposure needed
to produce a reddening/darkening effect
SPF = SUN PROTECTION FACTOR
- defined as effectiveness of sun creams
(Personal photo, Martin Nilsson)
SO, WHY NOT STAY OUT OF THE SUN
COMPLETELY ?...
THE GOOD…
UV-B
WOUND HEALING
VITAMIN D SYNTHESIS
...What is it?
…Where to get
it?
• We get vitamin D
from:
1. Exposure to
sunlight
2. Diet
3. Dietary
Supplements
Highest precursor [7dehydrocholesterol] are found in
the epidermal layer of skin.

Vitamin D has a wide range of functions
in human health.
Vitamin D → Sunshine Vitamin
Protects
against
heart
diseases
Strengthen &
Build bones
Prevent
diabetes
Prevent
high blood
pressure
(HBP)
Protects
against
cancers
Calcium
Homeostasis
Protects
against
autoimmune
diseases
1,25-DIHYDROXYVITAMIN D 3
•
•
•
Pre-vitamin D3 is synthesized in the skin when exposed to mid-ultraviolet
waves.
– Pre-vitamin D3 isomerized to vitamin D3 (cholecalciferol).
Cholecalciferol is hydroxylated in liver to form 25 hydroxycholecalciferol.
In proximal convoluted tubule is hydroxylated to 1,25
dihydroxycholecalciferol (active vitamin D3).
– Stimulated by PTH.
FREQUENTLY ASKED QUESTIONS…
HOW DO I PROTECT MY SKIN ?
12 – 3pm
30 mins
CAN I TAN IF I HAVE A LIGHT SKIN ?
WHAT ARE FRECKLES (EPHILIDES) ?
- Concentrated areas of melanin in the skin…activated by
sunlight
BAG OF PIGMENT
WHY DO WE GO GREY ?
FINALLY….
LOVE THE SKIN YOU’RE IN!!...
…..IT’S THE ONLY ONE WE’VE GOT!!!
Thanx !