A&P Quiz (Skin) Flashcards
Characteristics of skin
Cutaneous membrane
Subcutaneous tissue
Cutaneous membrane
the dermis layer (connective tissue, nerve, and muscle)
Functions of Skin and Hypodermis
Protecting inside of body
Excretion (salt, water, and organic wastes)
Maintenance of Temperature (insulation and cooling)
Production of Melanin (protection against UV)
Production of Keratin (protects against abrasion; water repellant)
Synthesis of Vitamin D
Storage of Lipids in adipocytes
Detection of touch, pressure, pain, and temp
Overview of Epidermis
Composed of Stratified squamous epithelium
NO BLOOD VESSELS
4 types of cells
5 layers
Keratinocytes
90% of epidermis cells – makes keratin
Melanocytes
8% – makes melanin that can be transferred to other cells with long cell processes
Langerhan cells
Related to macrophages, provides immunity by consuming pathogens that have gotten into the skin
Merkel cells
in the deepest layer of epidermis, but the most superficial sensory neuron compared to the rest; just for light touch
Keratin
Family of fibrous structural proteins
Layers (Strata) of the Epidermis
Stratum corneum (Highest) Stratum lucidum Stratum grandulosum Stratum spinosum Stratum basale (lowest) Come on Lets Go Skin Bathe
Stratum basale (also called stratum germinativum)
Deepest layer
Stem cells that constantly divide and replace other cells by being pushed up
Connected by desmosomes
Stratum spinosum
Called this way since they’re looking spiny under microscope
Just the basal cells pushed up
where langerhan cells are
8-10 cells held together by desosomes
Stratum Grandulosum
Start to fill with keratin in this layer
they’re going to die with the amount of keratin, nucleus starts to break down
Stratum Lucidum
Layer of dead cells only seen in “thick skin” (palm, soles of feet)
What makes thick skin thicc
3 to 5 layers of dead skin cells, filled with keratin
Stratum Corenum
25 to 30 layers of flat, dead skin cells filled with keratin and surrounded by lipids
Continuously sheds
Barrier to light, heat, water, chemicals, and bacteria
Friction stimulates callus formation
Keratinization and Epidermal Growth
Process of stem cells dividing into keratinocytes
pushed up towards surface and fills with keratin in process
4 week journey unless outer layers are removed by abrasion (then it’s faster)
Hormone EGF can speed up process
Keratinization and Epidermal Growth
Process of stem cells dividing into keratinocytes
pushed up towards surface and fills with keratin in process
4 week journey unless outer layers are removed by abrasion (then it’s faster)
Hormone EGF can speed up process
Psoriasis
Chronic skin disorder that causes abnormal keratin productions that causes cells to shed as silvery scales
A genetic issue that currently has no cure, but creams and anti-inflammatories can help alleviate symptoms
Can you restore damaged stratum basal cells?
New skin can’t regenerate if stratum basal and its stem cells is destroyed, but can move epidermis cells to cover the area
Melanocytes
located in stratum basal layer
Manufacture melanin
Package melanin into melanosomes (intracellular vesicles) that travels to keratinocytes
Genes determine the amount of melanin produced (around 6 genes that code for pigmentation) –> not the amount of melanocytes we have, we all have roughly the same regardless of our ancestry
Vitamin D
Derived mainly from the sun, but we can also get from dietary intake like fish and meat
Used for keeping bones hard AND cellular signaling
Synthesis of Vitamin D
UV stimulates production of compounds needed for calcium homeostasis
Sun stimulates 7-dehydrocholestrol –> cholecalciferol (Vitamin D3) –> converted in liver to 25-hydroxyvitamin D3 –> 25-hydroxyvitamin D3 –> converts to 1,225-dihydroxyvitamin D3 in kidney which helps to maintain calcium balance
Vitamin D hypothesis
evolution of lighter skin occurred in areas with less sunlight as a direct result of selection for more efficient Vitamin D synthesis
Vitamin D hypothesis
evolution of lighter skin occurred in areas with less sunlight as a direct result of selection for more efficient Vitamin D synthesis (ie: allows for better Vitamin D absorption)