system the epidermis and its layers Integumentary system Includes your entire outer layer of skin 16 of your total body weight accessory organs like hair nails and glands Consists of two major parts ID: 275816
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Slide1
Integumentary
system:
the epidermis and its layersSlide2
Integumentary
system
Includes your entire outer layer of skin (16% of your total body weight), accessory organs like hair, nails, and glands.
Consists of two major parts:
(1)
Cutaneous
membrane
(2) Accessory structuresSlide3
Cutaneous
membrane (skin)
Made up of two layers:
(1)
Epidermis
(superficial epithelium), and
Dermis
(underlying connective tissue)
(2)
Accessory structures
– Including hair, nail , exocrine glands. Located mostly in the dermis and protrude into the epidermal layer
(3) Subcutaneous layer deep to the dermis is known as the
hypodermis
; often not considered part of the
integumentary
system, but because its fibers extend into the dermis, we will include it hereSlide4
Structure of the skinSlide5
Function of the skin
(1) Protection of underlying tissues and organs against shocks, abrasion, and chemicals
(2) Excretion of salts, water, and organic wastes
(3) Maintenance of normal body temperature via insulation or evaporative cooling (sweating)
(4) Synthesis of vitamin D3
(5) Storage of nutrients – including lipids/adipose
(6) Detection of touch, pressure pain, and temperature stimuli and relaying information to the control center (brain)Slide6
epidermis
Recall epidermis composed of
stratified
squamous
cells for the purpose of protection
Most abundant epithelial cells are called
keratinocytesSlide7
epidermis
Keratinocytes
make up five layers of thick skin, and four layers in thin skin
Thick skin is found in the palms of your hands and soles of your feet
Thin skin is found everywhere else in your body
Thick and thin refer to the thickness of the epidermal layerSlide8
Epidermal layers of thick skin
Top layer of skin
Bottom layer of skinSlide9
Stratum
germinativum
/stratum
basale
Stratum
germinativum
, also known as stratum
basale
, is the bottom most layer of skin
Epidermal ridges
are found here, and they extend into the dermis.
Projections called
dermal papillae
creates an interlocking arrangement that increases the strength of the bond between the dermal and epidermal layersSlide10
Stratum
germinativum
/stratum
basaleSlide11
The contours of the skin surface follow the ridge patterns
Ridges on the palms and soles of feet increase the skin’s surface area and friction, helping to maintain grip
Ridge shapes are genetically determined, unique to you, and do not change throughout your life
Ridge prints located on your fingers are called
fingerprints
Stratum
germinativum
/stratum
basaleSlide12
Basal cells
dominate this layer. Basal cells are stem cells whose divisions replace skin cells lost to shedding at the skin’s surface
Merkel cells
are also found in this layer. Merkel cells are sensitive to touch.
Stratum
germinativum
/stratum
basale
Basal CellSlide13
Melanocytes
are pigment cells that give skin its color; they are also found in this layer
Stratum
germinativum
/stratum
basaleSlide14
Stratum
spinosum
Means “spiny layer”
Contains
Langerhans
cells, which are part of the immune system
Langerhans
cells
are responsible for stimulating a defense against:
(1) microorganisms that penetrate the epidermis
(2) superficial cancer cellsSlide15
Stratum
granulosum
Known as the “grainy layer”
By the time the cells reach this layer, they have stopped dividing and now begin to make lots of the protein
keratin
Keratin makes up our hair and nailsSlide16
Stratum
lucidum
Present only in thick skin
“Clear layer” filled with keratinSlide17
Stratum
corneum
Top layer of epidermis; consists of 15-30 layers of cells
Keratinization
or
cornification
, is the formation of protective, superficial layers of cells made of keratin
Dead layers of cells so tightly connected that when they slough off they separate as sheets of cellsSlide18
Epithelial Cell life cycle
Takes 15-30 days for epithelial cells to move from stratum
basale
/
germinativum
to the stratum
corneum
They stay in the stratum
corneum
for about two weeks before being washed/shedSlide19
Stratum
corneum
A dry layer, so few microorganisms can survive here
Layer is water resistant, but not waterproof. Water from inside the body slowly penetrates to the surface where it is evaporated. We lose ~500mL (1 pint) of water/day
This process is called
insensible perspiration
If this layer is damaged or lost (as in burns), the rate of water loss dramatically increases and you are at risk of dehydrationSlide20
Osmotic pressure
Recall from biology that freshwater will move into cells, causing them to SWELL
This is why when you take a bath your hands swell and look like raisins
Likewise, water will leave cells if placed in highly concentrated solutions, like
oceanwater
Although the process occurs slowly, it will accelerate the dehydration process in shipwreck survivors
After 51 hours
o
f exposure to
seawater and
w
earing glovesSlide21