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NSF > skin > Flashcards

skin Flashcards

1
Q

epidermis structure

A

squamous stratified epithelium made mainly keratinocytes
* variable thickness according use - species + anatomical location

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2
Q

layers epidermis

A
  1. stratum basale = single layer cuboidal cells in contact w BM. stem cells, dividing form new keratinocytes replace lost @ surface
  2. stratum spinosum = several layers keratinocytes bound tightly by desmosomes (cyt conts tonofilament)
  3. stratum granulosum = fewer layers, v basophilic, loads keratohyaline granules (only if epi v thick)
  4. stratum lucidum = dead cells, lost nuclei, translucent, keratinised (only if epi v thick)
  5. stratum corneum = flattened dead keratinised cells continuously sloughed (v basophilic

deep -> superficial

spinosum - spiky bc lots desmosomes
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3
Q

eosinophilic vs basophilic

A

pink vs purple

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4
Q

desmosomal prots

A
  1. desmoglein 1
  2. desmocollin 1
  3. E-cadherin
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5
Q

hemidesmosomal prots

A
  1. plakophilin 1
  2. keratins 5 + 14
  3. laminin
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6
Q

melanocytes

A

cells w tenticles to prod melanin + inject it in keratinocytes
* prod pigment (melanin) to reduce damage UV light on DNA
* mel synthed, packed in vesicles -> adjacent keratinocytes = lost when reach skin surface
* nucleus v close basement mem
* amount determines phenotypic characteristic skin pigment

in stratum basale, extensions bet stratum spinosum layers

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7
Q

Langerhans cells

A

macrophages for immuno surveillance in epidermis => cause rashes

= brown cells
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8
Q

merkel cells

A

sensory receptors in basal layer, associated w nerve endings

can see on slides

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9
Q

processes occurring in epidermis

A
  1. continuous proliferation of keratinocytes in basal layer
  2. migration, differentiation + keratinisation of keratinocytes
  3. squamous cells being sloughed off at surface
  4. protection from UV light
  5. immunosurveillance
  6. sensorial perception

==> relatively impermeable protective layer

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10
Q

dermis is

A

extracellular matrix w collagen etc + vessels + nerves/sensory corpuscles + adnexa (hair follicles, musc)

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11
Q

mols in extracellular matrix of dermis

A
  1. collagen
  2. elastic fibres
  3. GAG (hyaluronic acid)
  4. proteoglycan
  5. water
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12
Q

dividing dermis

A
  1. outer papillary - collagen less chunky
  2. reticular = bigger bottom layer
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13
Q

bv plexi in skin

A
  1. superficial plexus just beneath epidermis => nutrients to all epidermis
  2. mid plexus => supply adnexa
  3. deep plexus
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14
Q

pacinian corpuscle histology

A
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15
Q

hypodermis

A

== subcutis
layer where collagen ends, made adipocytes, connecting skin to musc etc below
* variable in thickness

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16
Q

label

A

hair follicle where hair grows from

dermal papilla cont bvs to supply whole structure

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17
Q

histology of hair folliclle

A
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18
Q

simple vs compound hair follicles species

A

simple = pig, horse, cow
compound = cat, dog, sheep, goat

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19
Q

primary vs secondary hair follicles

A

primary = may have additional apocrine gland asw
secondary = smaller + go into dermis/hypodermis less deep

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20
Q

life cycle of hair follicle/shaft

A
  1. anagen phase = growing
  2. catagen = regressing
  3. telogen = resting
  4. kenogen = latent (hairless)
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21
Q

what affects hair growth cycle

A
  1. photoperiod = times of day org exposed to light
  2. genetics
  3. age
  4. hormones
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22
Q

how does photoperiod affect hair growth cycle domestic animals

A

most shed coat seasonally under influence hormones prolactin + melatonin (proded in dark)
* dogs + cattle change in summer
* cats + rabbits -> winter coat in autumn, summer in spring

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23
Q

how hormones affect hair growth cycle

A

thyroid:
1. decr anagen (growth)
2. incr telogen (resting)

so hypothyroidism => bilat, symmetrical alopecia

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24
Q

sinus hair

A

whisker (also in toes)

special bc w/in wall of hair follicle are sinus of blood + nerves to understand environ around

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25
Q

sebaceous glands

A

exocrine gland prod sebum (oily) as aqueezed by contractions piloerector muscs
* pale staining, flask shaped
* secr by holocrine method
* excretory duct empties into hair follicle
* sebum = lipids: triglycerides, cholesterol esters, waxes (odourless until broken down by bac)

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26
Q

function sebum

A

oils hairs + forms oily film on skin to:
1. prevent water loss =/ waterproofing
2. lubricate skin
3. inhibit growth certain bac
4. spread sweat
5. territorial marker

skin not v perm water but not waterproof = route drug administration

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27
Q

what increases water resistance skin

A
  • sebaceous gland secretions
  • insoluble keratin w/in keratinocytes
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28
Q

regulation sebaceous glands

A

regged sex steroid hormones (androgens incr activity)
* more active after puberty
* larger + more productive in breeding season

used territorial marking + sexual attraction

29
Q

sebaceous glands in birds

A

none w feathers
* in preening, spread secretions from uropygial gland @ base tail

30
Q

sweat/apocrine/epitrichial glands

A

exocrine gland prod sweat (ultrafiltrate of blood plasma)
* for thermoreg (evap heat loss), excr, scent signalling
* simple cuboidal epithelium w myoepithelial cells
* symp adrenergic
* oily opaque secr odourless -> smell w bac breakdown
* cont myoepithelial cells

excr duct = 2 layers cuboidal => hair folicle/sweat pore to exit (merocrine)

common in domestics, less in primates

mid plexus
31
Q

ecrine sweat glands

A

for evaporative heat loss
* symp cholinergic
* watery NaCl sol modified by aldosterone
* odourless
* cont myoepithelial cells

common primates, less in domestics

32
Q

sweat glands diff species

A
  1. horse, donkey, cattle = abundant
  2. sheep + goats = moderate, on scrotum + inguinal region -> enhanced heat loss there
  3. dogs, cats, pigs = sparse, of lil thermoreg importance
33
Q

pig specialised skin glands

A

preputial glands @ opening foreskin => sexual attraction initiate mating behaviours sow

34
Q

sheep specialised skin glands

A
  1. infraorbital pouch => territorial marking
  2. interdigital on all limbs => fatty secr, mark footprints, signal other animals in flock

also in goats, deer

35
Q

specialised skin glands dog

A
  1. anal => fatty secr during pooing => signature on faeces for territorial marking
  2. tail gland (dorsal tail) => territorial marking

cats have tail gland too; anal = stink gland in skunks for defense

36
Q

mammary glands

A

modified sweat glands

v susceptiblle changes due hormones

37
Q

arrector pili musc

A
  • 45deg to hair follicle
  • mostly present in dorsal aspect
  • attached follicle wall to raise/lower hairs for thermoreg/social functions

super pink

38
Q

functions of skin

A
  • protection as boundary
  • thermoreg
  • secretion
  • sensory
  • pigmentation
  • vit D metabolism
  • immunosurveillance
39
Q

what determines temp

A

depends on balance bet heat input + heat output

40
Q

thermoreg defn

A

organism’s ability to keep body temp w/in certain boundaries, even when surrounding tempv diff

41
Q

core temp

A

= brain, thorax, abdom

mammals = endotherms = stable core temp

42
Q

normal core temp

A
  • range 0.5-1.0° over 24h
  • diurnal animals = lowest @ night + 1st thing
  • incr in metabolic rate = incr temp: growing, lactating, pregnant
43
Q

controlling body temp mammals

A

maintained by hypothalamus
* thermoreceptors on skin (skin temp) or in hypothal (blood temp)

symp ANS both ways, neg feedback control

44
Q

responses to cold stress

A
  • vasoconstriction
  • less sweating
  • hairs stand upright = contract erector pili musc to trap thicker layer air insulate
  • shivering = thermogenesis
  • adrenaline + thyroxine released
  • activate brown adipose tiss = thermogenesis
  • behaviour
45
Q

responses to heat stress

A
  • vasodilation
  • sweating/panting = evaporative heat loss
  • hairs lie flat
  • no shivering
  • no adrenaline or thyroxine release
  • behaviour = decr symp activity
46
Q

what happens when you relax/contract resistance arterioles

A
  1. blood shunted -> dermis thru subcut adipose tiss + blood heats skin
  2. decr bloodflow in dermis + subcut fat provides insulation from heat loss from vasculature
47
Q

normal core temp horse

A

rectal temp 37.5-38.5

48
Q

normal core temp cow

A

rectal temp 38.0-38.5

49
Q

normal core temp pig

A

rectal temp 38.5-39.0

50
Q

normal core temp sheep

A

rectal temp 38.5-39.5

51
Q

normal core temp cat

A

rectal temp 38.5-39.5

52
Q

normal core temp dog

A

rectal temp 37.5-39.0

53
Q

evaporative heat loss

A

evap requires heat E + causes insensible heat loss
* sweating, panting + wetting bod

horses sweat profusely, cattle/sheep moderate, pigs/dogs/cats minimal
-> pigs/dogs/cats reliant panting

54
Q

panting

A

rapid shallow breathing
* incr RR 30->300-350/min = natural oscillation frequency so lil E expended
* water to evap mostly from nasal turbs

dogs, cats, pigs, rumis + birds can

55
Q

what contributes heat input

A

not working, growing etc all E converted -> heat

60-70% heat prod in heart, brain, liver, kidneys (10% body mass)

56
Q

thermogenesis

A

incr basal metabolic rate by
1. shivering as antagonistic muscs contr simultaneously
2. incr secr of symp NS for rapid short-lived incr in metab = ox FAs in BAT
3. incr secr thyroid hormone - slow + prolonged
4. incr appetite

57
Q

behavioural responses to heat/cold stress

A
  • open/closed posture
  • seeking shade/heat
  • wallowing for evap heat loss
58
Q

thermo-neutral zone

TNZ

A

where additional E not required to maintain core temp (includes thermoreg mechs that use lil/no E

59
Q

lower critical temp

A

where animal must start heat prod to maintain body temp

60
Q

upper critical temp

A

cutaneous blood flow has reached max + extra E required to lose heat

61
Q

which homeostatic mechs have E cost

A
  1. evaporative heat loss - sweating/panting
  2. thermogenesis
  3. some behavioural changes like incr exercise
62
Q

chem forms of vit D

A
  1. vit D2 = constituent of plants
  2. vit D3 = cholecalcoferol, synthed in skin
63
Q

vit D synth in skin

A

7-dehydrocholesterol in dermis -UV-> cholecalciferol

inhibited by dense fur coat, heavy pigmentation

64
Q

pyrogens

A

systemic illnesses like viral infections release pyrogens
* incr hypothalamic set pt to higher val than normal => you’re acc really hot but you feel cold

65
Q

why production of melanin important

A
  • camouflage
  • mimicry
  • social comms
  • protect against harmful solar radiation (can dissipate over 99.9% absorbed UV)
66
Q

melanin

A
  1. eumelanins = black + brown
  2. pheomelanins = red + yellow
67
Q

what factors control pigment synth

A
  • genetics
  • local factors in skin
  • hormones
68
Q

process of melanin synth control

A

more MSH binding receptor = more tyrosinase = tyrosin -> eumelanin (derivative)

MSH prod stimmed by:
* UV light
* disease states
* external signals, e.g. for camouflage

controlled MSH-receptor binding

NSF (22 decks)

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