Lesson 7 Flashcards
dematology
scientific study and medical treatment of the integumentary system
integumentary system
consists of the cutaneous membrane (skin) and accessory structures like hair, nails, and glands
skin consists of two layers: _____ and _____
epidermis, dermis
Why does thickness range in the integumentary system?
it is mainly due to variation in dermis thickness, but skin is classified as thick or thin based on epidermis layers
_____ covers palms, soles, and corresponding surfaces of fingers and toes
thick skin
thick skin has… (3)
- sweat glands
- but no hair follicles
- no sebaceous (oil) glands
functions of the skin (5)
- protection
- vitamin D synthesis
- sensation
- thermoregulation
- nonverbal communication
general features of epidermis (3)
- keratinized stratified squamous epithelium
- avascular
- contains sparse nerve endings for touch and pain
five epidermal cells: keratinocytes
synthesize keratin, great majority of epidermal cells
five epidermal cell types: stem cells
undifferentiated cells that give rise to keratinocytes in the stratum basale
five epidermal cell types: melanocytes
synthesize pigment called melanin that shields DNA from ultraviolet radiation; only in stratum basale but have branches processes that distribute melanina via melanosomes
five epidermal cell types: tactile cells
touch receptor cells associated with dermal nerve fibers; in stratum basale
five epidermal cell types: dendritic cells
phagocytic immune cells that guard against toxins and microbes; found in stratum spinosum and stratum granulosum
layers of the epidermis: stratum basale
- single layer of stem cells and keratinocytes resting on the basement membrane
- also contains scattered melanocytes and tactile cells
layers of the epidermis: stratum spinosum
- several layers of living keratinocytes joined by desmosomes and tight junctions
- named after appearance
- contains dendritic cells
layers of the epidermis: stratum granulosum
- three to five layers of flat, living keratinocytes that start to dehydrate and die
- contains dark-staining keratohyalin granules
layers of the epidermis: stratum lucidum
- thin, pale layer only found in thick skin
- keratinocytes packed with clear protein eleidin
- cells here lack nucelus/organelles
layers of the epidermis: stratum corneum
- up to 30 layers of dead, scaly, keratinized cells
- resists abrasion, penetration, and water loss
why do cells that migrate away from the dermis no longer undergo mitosis?
there are no blood vessels in the upper levels of the epidermis; no oxygen and nutrients to support cells
over time, keratinocytes flatten, produce more keratin and lipid filled _____ _____
lamellar granules
how many days does it take a keratinocyte to reach the skin surface?
30-40
epidermal water barrier
located in the stratum granulosum; it is formed from lipids from keratinocytes as well as tight junctions between them
functions of the epidermal water barrier
- helps prevent dehydration
- does not prevent water absorption by the stratum corneum
dermal papillae
upward, finger-like extensions of the dermis
epidermal ridges
downward waves of epidermis
general features of dermis (3)
- well supplied with blood vessels, sweat glands, sebaceous glands, nerve endings
- elastic and reticular fibers
- houses hair follicles and nail roots
papillary layer of dermis characteristics (3)
- thin zone of areolar tissue
- allows for mobility of leukocytes and other defense cells
- rich in small blood vessels
reticular layer of dermis characteristics
- composed of dense irregular connective tissue
what are stretch marks?
tears in the collagen fibers of the reticular layer of the dermis caused by stretching of the skin
how does a blister form between the dermis and epidermis?
damaged blood vessels may cause serous fluid to seep out
two types of fibers found in the dermis
- collagen
- elastic
dermis: collagen fibers
- strong, resists stretching but can bend easily
- provides flexibility
dermis: elastic fibers
- permits stretching when pulled, recoils back to original length
- provides flexibility and stretching
skin turgor
caused by water in the skin; flexibility and resilience, pinched skin stays pinched after release
dermatitis
inflammation of the papillary layer; characterized by pain/itchiness and caused by infection, radiation, irritation
decubitus ulcers
bedsores caused by problems with dermal circulation
variations in skin and hair color are due primarily to type and amount of _____
melanin
where is melanin produced?
in melanocytes and stores in melanosomes
eumelanin
brown and black eumelanin; responsible for tan, brown, and black skin
pheomelanin
responsible for yellowish/reddish undertones of Asians/Native Americans and pinkish tones of white skin
other contributing factors to skin color (3)
- UV radiation stimulates melanin synthesis
- degree of show-through of dermal vessels and white collagen
- possible accumulation of carotene
carotene
used to produce vitamin A, needed for epithelial maintenance and pigment for photoreceptors for vision
cyanosis
blueness due to oxygen deficiency
erythema
redness due to increased blood flow to the skin
pallor
paleness due to decreased blood flow to the skin
albinism
white skin due to genetic lack of melanin
vitiligo
loss of skin color in patches due to loss of melanocytes, probably caused by autoimmune reaction to melanocytes
jaundice
yellowing due to bilirubin in the blood aka compromised liver funciton
hematoma
bruising, blood clotting under the skin
friction ridges
formed by dermal papillae; markings on the fingertips that leave prints
flexion lines/creases
- lines on the flexor surfaces of the digits, palms, wrists, and elbows
- marks sites where skin folds during flexion of joints
freckle
flat, melanized patch
mole (nevus)
elevated, melanized patch often with hair
hemangiomas (birthmarks)
patches of discolored skin caused by benign tumors of dermal capillaries
hypodermis (subcutaneous tissue) (3)
- layer of connective tissue beneath the skin
- contains more areolar and adipose tissue than dermis
- common site of drug injection bc of many blood vessels
subcutaneous fat
refers to subcutaneous tissue that is composed predominantly of adipose tissue
accessory organs to the skin
hair, nails, and cutaneous glands
soft keratin
makes up stratum corneum of skin
hard keratin
makes up hair and nails; more compact due to numerous disulfide bridges between keratin molecules
hair functions on different regions of the body (6)
- hair receptors alert us of parasites crawling on skin
- hair on trunk and limbs is mostly vestigial
- scalp hair retains heat and protects against sunburn
- pubic and axillary hair signifies sexual maturity and aid in transmission of sexual scents
- guard hairs (vibrissae) guard nostrils and ear canals
- eyelashes and eyebrows enhance facial expression and nonverbal communication
pilus (pili)
hair
hair follicle
slender filament of keratinized cells growing from a tube in the skin
vibrissae
guard hairs, located around nostrils and ear canals
a hair is also called a _____
pilus, plural: pili
slender filament of keratinized cells growing from a tube in the skin is called a _____ _____
hair follicle
Where does hair not cover the body? (6)
palmar, plantar, and lateral surfaces and distal segments of fingers and toes; lips, nipples, and parts of the genitals
what are the main contributors to differences in hairiness?
the texture and pigment of hair
three types of hair
- downy
- vellus
- terminal
downy hair (lanugo)
fine, downy, unpigmented hair that appears on the fetus in the last 3 months of development
vellus hair (2)
- fine, pale hair that replaces laugo by the time of birth
- two-thirds of the hair of women, one-tenth of the hair of men, all of the hair on children (except eyebrows, eyelashes, and scalp hair)
terminal hair (4)
- longer, coarser, more heavily pigmented
- eyebrows, eyelashes, and hair of the scalp
- after puberty, forms axillary and pubic hair
- male facial hair and some of the hair on trunk and limbs
_____ if the portion of hair above the skin surface, _____ is the portion below
shaft, root
hair matrix
mitotically active cells immediately above the papilla; growth center for hair
dermal papilla
bud of vascular connective tissue, provides nutrition to hair
bulb (hair)
root ends
medulla (hair)
core of loosely arranged cells and hair spaces
cortex (hair)
bulk of the hair, layers of elongated cells
cuticle (hair)
outermost region consisting of multiple layers of thin, scaly cells that overlap like roof shingles
two principle layers of the hair follicle
- epithelial root sheath
- connective tissue root sheath
epithelial root sheath
extension of the epidermis lying adjacent to the hair root; widens at deep end into a bulge, a source of stem cells for follicle growth
connective tissue root sheath
derived from dermis but a bit denser; surrounds epithelial root sheath
sensory _____ _____ entwine each follicle and respond to hair movements
nerve fibers
arrector muscle
bundle of smooth muscle attaching follicle to dermis; contracts to make hair stand on end
piloerection
hair standing “on end”
brown and black hair is rich in ______
eumelanin
red hair has high concentrations of _____
pheomelanin
blonde hair has intermediate amount of _____ and very little _____
pheomelanin, eumelanin
grey and white hair have little or no _____, and air is present in the _____
melanin, medulla
cross-sectional shape of hair: straight
round
cross-sectional shape of hair: wavy
oval
cross-section shape of hair: curly
relatively flat
functions of nails (2)
- improve grooming, picking apart food, and other manipulations
- provide counterforce to enhance sensitivity of fleshy fingertips to small objects
what are nails composed of?
thin, dead cells packed with hard keratin
what layer of skin are nails derived from?
the stratum corneum
nail plate
hard part of the nail; including overhanging free edge, nail body, and nail root
free edge of a nail
overhanging portion of the nail
nail body
visibly attached portion of nails
nail root
the section of your nails under the skin
nail fold
skin raised around the niail
nail groove
separates the nail fold from the nail body
cuticle (eponychium)
narrow zone of dead skin that overhangs proximal end of the nail
two types of sweat glands
apocrine and eccrine
apocrine sweat glands
- ducts lead to nearby hair follicles; produce sweat that is milky and contains fatty acids
locations of apocrine sweat glands
groin, anal region, axilla, areola, beard in men
what do apocrine glands respond to?
stress and sexual stimulation; inactive till puberty
bromhidrosis
disagreeable body odor; usually due to inadequate hygiene
eccrine (merocrine) sweat glands
- most numerous
- simple tubular glands produce watery perspiration that helps skin cool
where are eccrine glands especially dense?
palms, soles, forehead
myoepithelial cells (2)
- found in both apocrine and eccrine glands
- contract in response to stimulation by sympathetic nervous system and squeeze perspiration up the duct
insensible perspiration
not noticed; does not produce visible wetness of skin
- lose approx. 500ml/day
cutaneous transpiration
water loss from skin not due to sweating; water diffused between the keratinocytes and evaporates from the skin surface
disphoresis
sensible perspiration; sweating with wetness of skin in response to heat, exercise, and circulatory shock
- 1 L or more per hour may be lost during exercise
_____ _____ produce oily secretion called _____
sebaceous glands, sebum
what mode of secretion do sebaceous glands follow?
holocrine
ceruminous glands
modified apocrine glands found only in the external ear canal
- coiled simple tubular glands
- produce cerumen aka earwax
cerumen functions (4)
earwax
- waterproofs the canal
- keeps eardrum pliable
- kills bacteria
- makes guard hairs sticky to help block foreign particles
mammary glands
milk-prodicing glands that develop in females during pregnancy and lactation
mammary glands are modified _____ glands
apocrine
mammary ridges/milk lines
two rows of mammary glands in most mammals
polythelia
when people have additional mammary glands/nipples
skin cancer is caused by exposure to _____
UV rays
where does skin cancer occur the most?
head, neck, and hands
who is skin cancer most common in?
fair-skinned people and the elderly
three types of skin cancer
- basal cell carcinoma
- squamous cell carcinoma
- malignant melanoma
basal cell carcinoma
- most common
- least dangerous because it seldom metastasizes
what do basal cell carcinomas form from?
stratum basale
what do basal cell carcinomas look like?
small, shiny bump with central depression and beaded edges
squamous cell carcinoma
- chance of recovery is good with early detection and removal
- tends to metastasize to lymph nodes and may become leathal
what do squamous cell carcinomas form from?
arises from keratinocytes of the stratum spinosum
where do squamous cell carcinomas generally form?
scalp, ears, lower lip, or the back of the hand
what do squamous cell carcinomas look like?
raised, reddened, scaly appearance; later forming a concave ulcer
melanoma
- less than 5% of skin cancers
- can be successfully removed if caught early, but usually fatal if metastasizes
who do melanomas occur in most often?
men, redheads, people who had severe sunburn as a child
what do melanomas derive from?
melanocytes
first-degree burn (3)
- only involves the epidermis
- redness, slight edema, pain
- heals in days
second-degree burn (4)
partial-thickness burn
- involves part of the dermis
- may appear red, tan, or white
- blistered and painful
- two weeks to several months to heal, may leave scars
third-degree burns (3)
- involves all of the dermis and often some deeper tissues
- often requires skin grafts
- needs fluid replacement, infection control, and supplemental nutrition
autograft
tissue from another location on the same person’s body
allograft
tissue from an unrelated person, usually deceased donors
artificial and lab-based approaches for third-degree burns are in progress with epidermal growth factor that: (4)
- promotes division of germinative cells
- accelerated keratin production
- stimulates epidermal repair
- stimulates glandular secretions
