today we'll be discussing the integumentary system which is probably
one of the least well known
organ systems in the body even though it is very important
and actually makes up about one-sixth of our total body weight
the integumentary system is divided into two major parts
the cutaneous membrane and the accessory organ structures
the cutaneous membrane can further
be divided into different regions including the epidermis
and the dermis there's also a hypodermis
which consists of connective tissue and fat tissue
which separates the integumentary system
from other organs but it's not technically considered part of the
integument
the epidermis can be further divided into five different layers
these include the stratum corneum the stratum
lucidum the stratum granulosum
stratum spinosum and stratum basale
remembering the different layers of the epidermis might be tricky
so what I like to employ is a pneumonic this helps remember the different layers
pretty well so what I like to do
is write can leafs
get Stanley
back
your hockey fan
and you like the leafs this will help you now remember you don't always have to use
these pneumonics or pheumonics you see in textbooks you can always make your own
up
and it's actually encouraged because it will help you remember them better so these
are the different layers or the stratum corneum
lucidum
granulosum
spinosum
and finally
basale so that's just one way to remember the five different layers of
the epidermis
now on to the dermis the dermis consists of two layers
the papillary and the reticular the reticular layer is thicker and denser
than the papillary layer and it is here where you find many
but not all of the accessory structures of the integument these include
hair shafts, pores, tactile receptors
subacous glands, arrector pili muscle
sweat glands and ducts, hair follicles
and nerve fibers. As you can already see
there are many different structures within the integumentary system
these give rise to its numerous in various functions
including: 1. to protect underlying organs from
impact abrasions fluid loss as well as exposure to chemicals and foreign
pathogens
2. maintaining normal body temperature
3. the excretion of salts and water
4. the production melatonin
which gives our skin is pigment 5. the production of karatin
6. storage of fuel reserves in the form of lipids
7. sensation of touch, pressure,
pain and temperature and the subsequent transmission of these signals
to the nervous system and 8. the synthesis of vitamin D3
which is the main topic up this video. Vitamin d3
is essential for the maintenance and the development of strong and healthy bones
it is used to produce a hormone called calcitriol
which helps increase the absorption of
calcium and phosphate in the digestive tract
so how does the integumentary system fit into this
well it's the integumentary system
more specifically the epidermis that creates
vitamin D3. Take a look at the diagram on the board
ultraviolet rays from the sun hit our skin
and actually cause certain layers in the epidermis
to create cholecalciferol. The layers that do this
are stratum spinosum and the stratum basale
what happens is there's a steroid molecule that lies in stratum
spinosum. Once UV rays hit the skin
this converts that to cholecalciferol
Cholecalciferol then enters the blood
it circulates to the liver where it is then converted
to a molecule called calcidiol
that calcidiol the re-enters the bloodstream
and you can see that it travels to the kidney. It is calcitriol
that's the main hormone that's responsible for the increased absorption
of calcium as well as phosphate from the digestive tract
if we do not have enough calcitriol production in the body
this can lead to impaired bone growth and maintenance
In children rickets can develop when there's a lack of calcitriol
In adults osteomalacia occurs this is the softening of bones
These disorders have been prevented however in more recent years
as foods and beverages such as milk have become fortified with vitamin d3
nonetheless integumentary system still plays a large role
in maintaining normal calcium levels within the blood
and therefore maintaining strong healthy and bones