L2 Skin

Question 1

what system and derivatives is skin?

Answer 1

integumentary system (derivatives include hair, nails, sweat and mammary glands)

Question 2

is skin the largest organ in the body?

Answer 2

Yes its 15-20% of body weight and covers 1.5-2m^2

Question 3

functions of skin?

Answer 3

barrier
temperature regulation
excretory organ
synthesis of vit d
sense organ

Question 4

types of barriers

Answer 4

water loss - prevents dehydration -> important for burns
microorganisms - physical barrier-> oil of skin is antibacterial and sweat (low pH 6.3 vs 7.4) so antimicrobial as bacteria find it hard to survive
UV radiation - melanin

Question 5

is skin major source of excretion?

Answer 5

no, sweat excretes salts, toxins and drugs

Question 6

how is vit d produced?

Answer 6

produced by action of UV light where precursor becomes vit D with UV light
vit D important for bone growth (Ca2+ metabolism)
where a deficiency causes rickets (malformed, weakened bones)
so increased suncare = increase rickets since less vit d

Question 7

what senses are covered by skin?

Answer 7

touch, pressure, heat, cold, pain

Question 8

3 layers of skin

Answer 8

epidermis (outer)
dermis (middle)
hypodermis (inner) aka subcutaneous layer

Question 9

epidermis structure

Answer 9

made of stratified squamous epithelium
consists of 5 zones

Question 10

stratum granulosum

Answer 10

keratin becomes stronger
produces oils -> waterproofs the skin

Question 11

stratum spinosum

Answer 11

provides strength to epithelia
cell-cell contact
spot desmosomes

Question 12

stratum spinosum

Answer 12

provides strength to epithelia
cell-cell contact
spot desmosomes

Question 13

stratum corneum

Answer 13

dead cells packed with keratin
40 layers

Question 14

stratum basale

Answer 14

stem cells

Question 15

basal lamina

Answer 15

epithelial cells attach to cells below

Question 16

cell types

Answer 16

keratinocyte - produces keratin -> provides strength
melanocyte - found in stratum basale
merkel cells - mechanoreceptors (detect touch)
langerhans cells - phagocytes

Question 17

epidermal proteins - keratin

Answer 17

key structure of outer skin layer and hair and nails
keratin of hair and nails more tightly packed
contains cyestine -> formation of cyestine bonds -> covalent bonds -> increases strength
more cyestine bonds skin < hair < nails
keratin forms intermediate filaments which are tough + insoluble, provides strength, protection and waterproofing for skin

Question 18

epidermal proteins - melanin

Answer 18

production occurs after exposure to UV radiation, causing skin to visibly tan
released by melanocytes and TAKEN UP by keratinocytes
darker skin is due to more ACTIVE MELANOCYTES, not GREATER NUMBER
absorbs light well, can dissipate over 99.9% of absorbed UV and protect skin cells from UV radiation damage