normal skin and nail

lecture 1

what is the largest organ of the body

skin- average 4kg covering 2 square meters

two types of skin

glabrous ( smooth and without hair like the palms or soles of the feet)

hairy

what are the main functions of the skin

protections ( trauma, infection)

sensation

thermoregulation

excretion

metabolism ( vit d production

social interaction

how does the skin facilitate protection

acts as a physical barrier against

• trauma

• bacterial invasion

• excessive loss of fluids and proteins

protects tissues and structures from mechanical injury

immune protection

• langerhans cells

• tissue macrophages

• mast cells

skin pigmentation to protect against uv

• melanin- (dont want UVA- long form uv radiation as it can alter dna)

how does the skin facilitate sensation

is filled with nerve endings for pain pressure and temperature)

• the nerve fibers originate from the nerve root along the spine to supply skin ( dermatomes)

• loss or reduction of sensation leads to increased chances of injury

how does the skin aid in thermoregulation

regulates through orchestrated effort involving

• nerves

• blood vessels

• glands

skin is the barrier between internal and external environments so it senses and adjusts accordingly

• when skin is exposed to cold / internal temperature falls

  • blood vessels constrict reducing bf to preserve body heat

• when skin is hot ( internal temperature rises)

  • tiny arteries in the skin dilated increasing bf and sweating so the body can cool

how does excretion help thermoregulation of the skin

excretes water, electrolytes and waste products through over 2 million pores to release water and body wastes to the air, each day an adult loses about 500ml of water through the skin

how does the skin impact metabolism

when exposed to sunlight the skin synthesizes vit d

• it then transmits to other areas of the body

• assists in mineralization of the bones and teeth

what is meant by social interaction in regards to the skin

• has a psycho social function linked to other aspects like image physical attraction and communication

• damage to the skin can perpetuate functional and physiological consequences

  • impacts self esteem

what is skin composed of

layers of epidermis, dermis, appendages ( hair, nails glands)

sub cutanous fat

• fascia and muscle

what are the layers of the epidermis

stratum corneum

stratum lucidum

stratum granulosum

stratum spinosum

stratum germinativum/ basale

basement membrane/basal lamina

what is the epidermis and its purpose

thin outermost layer of the skin

• continually regenerates ( q21-28 days)

• sheds the outermost cell layer during hand washing

function

• barrier to water loss

• protects against mechanical damage chemicals and pathogens

how many layers is the epidermis

4 layers typically but 5 on sole and palms

• stratum corneum

• stratum lucidum- only palms and sole

• stratum granulosum

• stratum spinosum

• stratum germinativum/basale

come lets get sun burnt