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)
Metabolism of Folate
Vitamin essential for DNA synthesis and cell replication
Exposure to UV radiation causes breakdown of folate in the bloodstream
people with light skin and live in sunny areas can have folate deficiency
Cyanosis
blueness resulting from deficiency of oxygen in circulating blood (or cold weather) (that’s why they tell you not to wear nail polish during surgery so they can see if your nails are blue or not)
Erythema
Redness due to dilated cutaneous vessels (anger, sunburn, embarrassment)
Palor
paleness due to lack of blood flow
Jaundice
yellowing of skin due to excess of bilirubin in blood (liver disease)
Hemangiomas
Birthmarks –> just weird random errors that happened during embryonic growth
can be caused by overgrowth of blood vessels, melanocytes, fats, fibroblasts, or keratinocytes
Freckles and moles
Aggregations of melanin
You aren’t born with all of them, you get more as you get older. Genetic-based, but you accumulate more with more sun exposure
Papillary Region
Top 20% of dermis
Has loose CT (areolar) and elastic fiber (provides the elasticity in skin so when you pull it, it snaps back)
Has dermal papillae –> fingerlike projections that the dermis rests on
Functions of Papillary Region
Anchors epidermis to dermis
Contains capillaries to feed epidermis
Contains Meissner’s corpuscles (touch) and free nerve endings (pain and temp)
Reticular Region
Dense irregular connective tissue (NOT RETICULAR TISSUE)
Reticular means “net-like” –> describing all the fibers in the region that act like a net
Contains interlacing collagen and elastic fibers
Packed with oil glands, sweat gland ducts, fat, and hair follicles
Also provides strength and elasticity to skin
How are fingerprints formed?
Caused by sweat glands on fingertips and dermal papillae that are formed in fetus when the epidermis conforms to dermal papillae
Helps to increase grip so you can grasp the cock
Types of skin
Thin skin and thicc skin
Thin Skin
Covers most of the bodyThin epidermis (.1 to .15 mm) that lacks stratum lucidum, lacks noticeable epidermal ridges and fewer sweat glands
Thicc Skin
thicc epidermis (.6 to 4.5 mm) with distinct Stratum lucidum
Hypodermis (subcutaneous layer)
more adipose (fat) than dermis Functions: energy reservoir and thermal insulation Hypodermic injections (good area to get injections since there's lots of blood vessels)
Accessory Structures of the Skin
Epidermal Derivatives
Structures that originate in epidermis and during embryonic development that push inwards
(includes hair, oil glands, sweat glands (glands are epithelial tissue!), and nails)
Structure of hair
shaft – visible
root – below surface
follicle – surrounds the root and helps it to grow
bulb – base of the hair
Hair related structures
Arrector pili (smooth muscle in dermis that contracts with cold or fear --> forms goosebumps; in nonhuman animals, it helps to trap heat and makes them look bigger) mainly vestigial for us Hair root plexus (sensory neuron surrounding the base of the hair follicle, detects hair movement even if you're sleeping and someone pulls just one hair strand)
Hair and nails
Stratum corneum of the skin is composed of pliable soft keratin
Hair and nail composed of hard keratin (two cystine molecules coming together to form cysteine)
Hair and nails
Stratum corneum of the skin is composed of pliable soft keratin
Hair and nail composed of hard keratin (two cystine molecules coming together to form cysteine)
Functions of Hair
In humans too thin to provide warmth, but can alert s to insects or parasites crawling on the skin
Scalp hair provides heat retention and sunburn cover
Beard, pubic, and axillary hair indicates sexual maturity and helps to distribute sexual scents (ie: how people closely related to us doesn’t smell good)
Guard hairs and eyelashes prevent foreign objects from getting into nostrils, ear canals, or eyes
Eyebrows help to express emotions
Characteristics of human hair
found almost everywhere, but differs between individuals in texture and color
3 types:
lanugo (fine, unpigmented fetal hair that are mostly shed before birth)
vellus (fine, unpigmented hair of children and adults –> peach fuzz, turns terminal in puberty for bois (and michelle))
Terminal hair – coarse, long, deeply pigmented hair
