Unit 4 - Integumentary Flashcards
integument functions
protection
prevents desiccation (moisture removal)
helps maintain body temp
excretes salt, water, waste
receives sensory info
synthesizes vit D
stored nutrients
*most important = barrier
- maintains internal environment by preventing electrolyte + water loss AND by stopping external toxins from getting in
3 skin layers
1) epidermis
2) dermis AKA corium
3) hypodermis AKA subcutaneous
epidermis
above basement membrane
- keratinized stratified squamous epithelial cells
- no vessels
dermis
tough layer below epi
- dense irregular CT
- vessels
hypodermis
- adipose
- thermoinsulation + injury protection
cell type: keratinocyte
majority of skin cells
- made in basement membrane.
- keratinization: losing nucleus and dying
- sloughed at surface
- keratin makes waterproof
more cell types
melanocyte: produce melanin
- all animals have melanocytes, but the melanin produced varies (albinos produce none)
- pigment released in vesicles -> up to keratinocytes -> colour given
- coat colar = presence/absence of melanin granules in keratinocytes + hair.
- sun exposure increases melanin synthesis
- protects from UV
- decreases w/age
langerhans (macrophage)
- phagocytize microinvaders
merkel
- sensory nerve endings
- basal layer of epidermis
hairless epidermis layers
1) stratum corneum (horny)
2) stratum lucidum (clear)
3) stratum granulosum (granular)
4) stratum spinosum (spiny)
5) stratum basale (basal)
hairy epidermis
1) stratum corneum
2) stratum spinosum
3) stratum basale
- scalelike folds on skin surface where hair grows out of
- tactile elevations = epidermal papillae
- tactile hairs = tylotrich
-> sense of touch
dermis
greatest portion of integument (‘the hide’).
- highly fibrous
- dense irregular CT (collagen, elastic, reticular fibers)
- give strength
- can be tanned to make leather
other components:
- hair follicles, nerve endings, glands, smooth muscle, blood vessels, lymphatic channels, fibroblasts, adipocytes, macrophages
dermis layers
1) papillary
- thin, superficial
- just below epi
- dermal papillae
- looping vessles
- nerve endings + meissner’s corpuscles (touch)
2) reticular
- majority.
- indistinct boundary b/w papillary
- parallel collagen fiber bundles (make incisions along these lines for faster healing)
- dermal folds AKA flexure lines at joints
hypodermis
thick layer
allows skin to move freely over underlying structures
- loose areolar tissue layer w/ adipose, blood + lymph vessels, nerves
- continuous w dermis
- pacinian corpuscles (special type of touch receptor for heavy pressure)
paw pads
thick fat + CT covered by thick stratum corneum in form of conical papillae
- shock absorber
- insulates heat/cold
- protects from rough ground
- all 5 layers
- exocrine glands (other than horses, only location of sweat)
ergots + chestnuts
dark horny bits on horse legs
- vestiges of digits
chestnuts: medial on each leg at carpus/tarsus
ergots: smaller, hidden under hair on fetlock, caudal
planum nasale/nasolabiale
- usually pigmented
- aglandular in SAm glandular in sheep + cattle
- dogs lick nose to keep it moist, cows lick nose to keep it clean (so a runny nose might be a sign a cow is sick!)
planum nasale:
- top of nose in cats, pigs, sheep, dogs
- polygonal plates in dogs
planum nasolabiale:
- cow muzzle
- hairless
cutaneous pouches in sheep
infoldings of skin w/hair, sebaceous and oil glands
3 locations:
- infraorbital
- interdigital
- inguinal
fatty smelly yellow secretion dies and sticks to skin
skin injury response
PRISH
pain (licking, chewing, scratching)
redness
immobility (loss of function)
- alopecia
- thickening (lichenification)
- wrinkling
- melanosis (pigmentation)
swelling
- edema
heat
- other things related to exudate: crusting, scabbing, pustules
allergies
often manifest as skin issues
eg. recurrent ear/anal sac infection
- dogs chewing at paws
- cats compulsive grooming -> alopecia
- parasitic dermatitis (flea allergy) presents on back, abdomen, and tail
hair
essential for survival
- maintains body temp (traps air, dark colors absorb light)
- protection via camouflage
PARTS
1) shaft (visible above skin)
2) root (below skin)
2a. plexus: web of nerve endings around root
3) follicle (invagination of epidermis into dermis + hypo)
3a. hair bulb: deepest part of follicle, expanded into a hollow area
3b. papilla: mound of dermal cells at base of bulb
3c. matrix: dividing epithelial cells covering papilla, nourished by vessels below
* compound follicles = multiple strands from one pore (3 in dogs)
layers:
1) medulla: core
2) cortex: thickest layer, keratin
3) cuticle: thin surface shingle-like layer
- as cells divide in matrix -> old cells pushed up -> keratinized + die -> makes hair
hair growth
anagen = growth
catagen = transition
telogen = resting
telogen = bulb separates from dermis (hair falls out + new growth starts
- telogen effluvium = shedding
- can happen seasonally, due to disease, or hormonal changes (eg. ‘blowing the coat’ in bitches after parturition)
hair colour
melanin made in base of follicle -> transferred to corticol + medullary cells of hair
types of melanin: orange, black/brown, none (albino = white)
hair types
1) primary AKA guard
- straight, thicker and longer
2) secondary AKA wool-type
- softer and shorter
- often waxy (lanolin -> waterproofer)
- compound follicle often guard hair surrounded by wool hair
3) tactile
- sinus, whiskers, intermittently mixed in coat
- feelers, highly innervated follicle.
- stiff
arrector pili muscle
smooth muscle at each follicle
- innervated by sympathetic NS
- contration pulls hair erect
sweat glands AKA sudoriferous
watery liquid to help cool the body
- all over entire body, but only horses really sweat
1) eccrine/merocrine: empty onto skin surface
2) apocrine: empty into follicles
sebaceous glands
in dermis
- produce sebum
- simple or complex alveolar structure
- empty into follicle OR directly into skin (eg. lips, labia, penis, anus, eyelid, ear canal)
- hormone sensitive (increase at puberty)
- sebum bidning to dead skin cells -> blocked duct opening -> duct ruptures -> releases bacteria into epi/dermis -> inflammation
in sheep sebum = lanolin
- oily lipid
- arrector pili muscle compresses gland -> sebum pushed out of duct into follicle
- coats hair and surrounding skin (traps moisture, keeps soft + waterproof, reduces infection risk)
tail/chin glands
oval region at base of tail in cats/dogs
- large sebaceous glands
- coarse, oily hairs
- help animals identify each other
- more noticeable in males (‘stud tail’ in cats)
- also on chin of cats
- cyst prone
anal sacs
lined with sebaceous + apocrine sweat glands
- expressed when defecating (to mark territory) OR when scared
- connected by single duct to lateral of anus
- can become blocked
anal sac disease:
- infection
- don’t like to sit
- lick anal area
- scooting
- painful defecation
- rupture and drain pus if severe
- may be sign of allergies
- treatment: digital pressure, flush with catheter + warm water, surgical removal possible
claws/hooves
traction, climbing, defense, attack
*nails differ = only partial coverings
clawed mammals
bear most weight on foot pads
- retractible in all felids except cheetah
- declaw: amputation of P3 on each digit
hoofed mammals
bear most of weight on horn
ruminants: only digit 3 + 4 weight-bearing
- weight-bearing hooves called ‘lateral/medial claw’
- cow hoof like horse, only no frog + 2 claws
horses: only digit 3 bears weight
dewclaws
remnants of digits
- dogs: remnant of 1st digit.
- cow, pig, sheep: lateral AND medial dewclaws (2nd + 5th)
- only pigs have bones in dewclaws
horse hoof parts
1) hoof wall
- equivalent ot fingernail
- toe, quarters, and heel regions
- thick at toe, thin at heel
- vertical lines ‘horn tubes’
- may have horizontal ridges (period of growth)
- grows from coronary band -> down
- walls expand during weight-bearing
2) corium
- like a modified dermis
- underlying sensitive tissue
- attached to periosteum of distal phalanx
- blood vessels + nerves
- divided into:
coronary corium + perioplic corium, laminar corium, sole corium, frog corium
a. perioplic band: narrow region at proximal border of hoof
- equivalent to cuticle
- epidermal cells produce external layer of hoof wall
b. coronary band AKA coronet
- wider band distal to periople
- produces middle layer of hoof wall
- thick, weight-bearing layer
- grows from here -> downward
3) laminae
- connects hoof wall to corium (which is bound to P3)
- lets hoof wall grow out by sliding over each other
- only dermal laminae sensitive
4) sole
- bottom of hoof
- concave: not weight-bearing, but improves foothold
- no nerves/vessels superficially
- white line = junction of fool wall + sole
5) frog
- triangular structure w/central sulcus (cleft)
- cushions heel, reduces slipping, helps pump blood back up leg from corium during weight bearing
- digital cushion = thick pad of fat below frog
- sulci = valleys b/w edges of frog, must be scraped out w/hoof pick
shoeing
prevents excessive expansion of hoof during wight-bearing
- improves traction
- makes a barrier b/w ground + hoof -> injury protection
- combined w/trimming
hoof cartilage
lateral + collateral = pair that attach to angles of P3 and extend into the heel just above coronary band
- work w/frog + digital cushion to pump blood through foot
- frog + digital cushion flatten/widen during weight bearing
- puts pressure on walls, bars, and collateral cartilage
-pressure forces blood up
horse hoof bones
short pastern: P2
navicular: distal sesamoid
coffin bone: P3
- covered w/laminar coreum which interdigitate w/laminae of hoof
laminitis AKA founder
inflammation of laminae attaching hoof wall to corium
- usually front feet, will stand w/front feet out + hind limbs under (adjusting weight)
- feel hot to touch, increased digital pulses
- cause: diet -> sudden grain increase or fresh spring grass ingested
- starch + fructans (from grass) aren’t digested in SI and pass to LI -> bacterial overgrowth in LI -> toxins produced and absorbed
- swelling trapped by wall -> compression inhibits blood flow to corium -> corium degenerates
- wall + corium attachment lost -> pedal bone rotates/sinks within hoof -> pressure on sole/perforation of sole
- sole itself may sink.flatten
- hoof wall develops ridges and curls up at toe
treatment: pain + anti-inflammatory meds
- ice: prevents laminae breakdown
- shoeing/trimming, feed changes (but takes months)
prevention:
- limit high carb feed
- be careful of sudden introduction to lush pastures
- retained placenta from metritis can be complicated by laminitis, monitor feet carefully
sandcracks
vertical cracks
- named for toe/heel/quarter
- begins at solar border = from improper trimming
- begins at coronary band = from hoof defect
- dry hoofs more vulnerable
thrush
degenerating frog
- from filth + microorganisms
- black necrotic area
contracted foot/heels
foot narrower than normal
- from lack of frog pressure or improper shod
- front feet usually
- can cause lameness: ‘hoofbound’
heels:
- heels drawn in, bars almost parallel to frog -> frog reduced
navicular disease
chronic degenerative navicular
- older horses
- usually front feet
- trauma of racing + defective shoeing contribute
- begins w/cartilage loss + bursa inflammation
- common cause of ‘heel pain lameness’
bruised sole
direct injury from stones/irregular ground
- poor shoeing predisposes
- could cause lameness
bovine foot rot
inflamed interdigital space + coronary region
- caused by microorganisms
- signs: smell, redness, swelling, discharge
- responsive to antibiotics
bovine interdigital dermatitis AKA slurry heel
infection of heel bulb + interdigital skin
- lameness rare
- treat w/coppertox (topical disinfectant)
bovine interdigital fibroma AKA corns
proliferation of tissue of interdigital cleft
- associated w/foot rot + interdigital dermatitis
- mass of CT projects between claws
- walking painful as corn increases
bovine overgrown hoof
long hoof wall (usually lateral claw)
- base narrow conformation
- lateral wall curls under sole
- toe long
bovine hoof wall fissures
vertical/horizontal
- if found in one claw, check opposite foot too
- vertical (sandcracks) = overgrown claw -> abnormal weight bearing -> possible laminitis (more likely in dry weather)
- horizontal (thimbling) = mature dairy cattle following laminitis, usually affects all 8 claws
bovine laminitis
same as horse, but only mild pain
- necrotic toe lesions result
bovine ulcerations of the sole
- common in dairy
- front feet of bulls
- rear feet of cows
- ulcers in the sole -> lameness
horn
bony growth w/epidermal covering
- similar to hoof: corium binds keratin tubules bound to periosteum of underlying bony core
- become hollow ~6 months
- male + female
- usually permanent + grow continuously
- pronghorn antelopes: only species to shed horns annually
polled = no horns in a species that normally has horns
- polled breeds: bred to have no horns
antlers
typically only males
- shed annually
- bony growth nourished by velvet outer
- CT ring forms like tourniquet around base once fully grown -> makes velvet slough -> antler hardens
- late fall/winter the bony base connecting to skull weakens -> falls off
- antler harvest = painful
