Lesson 1 notes Flashcards
What is the thickness of skin?
0.5 to 3 mm
What is the surface area of skin?
3000 square inches
How many cells are contained in one square inch of skin?
3 million cells
What are the functions of skin?
Protect against infection, desiccation, harmful light rays Maintain body temp Receive stimuli from environment Stores chemical compounds Excretes waste products Synthesizes vitamin D
Name the thinner outer layer of the skin.
Epidermis
How many layers comprise the epidermis?
4 (palms of hands and feet have 5)
Which layers of the epidermis regenerate the cells of the epidermis?
Stratum Basale
Stratum spinosum
What is the waterproofing protein that forms in cells as they move towards the surface of the epidermis?
Keratin
What is the outermost layer of the epidermis?
Stratum corneum
How often is an epidermal cell shed and regenerated?
28-30 days
How many rows of cells are in the outermost layer of the epidermis?
25 to 30 rows
What are epidermal cells called?
keratinocytes
What other cells are found in the epidermis and are protective?
melanocytes and langerhans cells
What layer of skin is deep to the epidermis?
Dermis
What does the dermis contain?
blood vessels, nerves, glands, hair follicles
What are the three appendages of the skin?
hair
glands
nails
What is the soft hair that covers the body?
Vellus
What do appendages develop from?
Embryonic epidermis
What is the coarse hair that develops at puberty?
terminal also includes hair on scalp and eyebrows
What are the three parts of a hair?
shaft
root
follicle
What layer of the skin creates a hair follicle?
The epidermis
What structures are associated with hair follicles?
Sebaceous glands
arrector pili muscles
What glands are associated with the skin?
Sebaceous glands
Sweat glands
What are the two types of sweat glands?
apocrine - develop at puberty, located in the axilla, pubic region, and breast areolae.
eccrine - distributed throughout the skin
What is the function of a sebaceous gland?
secrete sebum (oil) which protects the hair and skin from becoming too dry
What are the parts of the nail?
free edge nail body nail root lunula (white area at proximal end) cuticle (epidermis around the nail) nail bed (epidermis under the nail)
What three things determine skin color?
Melanin
Carotene
Blood in the Capillaries
What is a freckle?
Melanin that forms in patches
How does UV radiation affect melanocytes?
It increases enzymatic activity which produces more melanin. Eventually, epidermal cells take up the melanin by phagocytosis and tanning has occurred.
What pigment is found in people of Asian decent?
Carotene
What is an example of an epidermal ridge?
fingerprints
What is a line of cleavage?
predominant direction in which collagenous fibers run.
surgeons attempt to follow these lines to reduce scarring.
At what time do you do a dermatological exam?
The same time you do the history.
Gram Stain
performed on lesions suspected of bacterial infection.
Guides antibiotic selection
Tzanck smear
Performed on lesions suspected of viral infection.
Positive result when giant, multinucleated cells are identified
KOH prep
Performed on lesions suspected of fungal infection.
Septated - tube-like structures - dermatophyte infection (tinea)
Budding - sausage-like structures - candidal infection
Direct examination of pathogen
Done in the case of scabies.
Mites, eggs, and feces can all be seen
Cultures
Done to identify all types of pathogens.
Generally include a sensitivity, to show which antibiotic will be effective.
Punch Biopsy
Cut through epidermis, dermis, and subcutaneous tissues.
Often utilized if the entire lesion cannot be easily removed, and suspected to be inflammatory.
Wedge (excisional) Biopsy
Cut through the epidermis, dermis, and subcutaneous tissues.
Method of choice for most neoplastic processes.
Shave Biopsy
Cut through the epidermis and dermis only.
Useful for lesions that are limited to the epidermis.
Tests for allergic sensitization identification:
Patch testing
Photopatch testing
Prick testing
RAST (radioallergosorbent test)
