Common Integument Flashcards
Skin
Function
Covers external surface of the body (barrier)
Perforated by natural openings (mouth, anus), blends into MMs that line the openings
Function:
Protection~ underlying structures of the body + specialised thickened regions of the skin (footpads) provides protection against physical trauma>invasion of microorganisms>sebaceous glands secrete an antiseptic sebum onto the skin’s surface>waterproof barrier, prevents drying out/water-logging>pigmented areas (skin+hair) protect against UV
Sensory~ nerve endings to detect temperature, pressure, touch and pain>monitors external environment
Secretion>glands produce secretions directly onto the surface of the skin>sebum (sebaceous), sweat (footpads and nose), pheromones (specialised skin glands)
Production~ UV light from the sun converts 7-dihydrocholesterol (sebum) into Vitamin D>activated in the kidney + liver increases uptake + metabolism of dietary calcium
Storage~ fat stores under skin (adipose tissue/subcutaneous fat)>fat is an energy store + insulating layer
Thermoregulation~ skin prevents heat loss, diverts blood away (vasoconstriction), erect hairs trapping insulating air>heat lost by sweat (not much in dogs and cats = due to footpads and nose being the only active sweat glands>panting
Communication~ pheromones (natural scents, intraspecific)>visual (hackles raised, threatened)
Skin
Structure
Epidermis:
-avascular, nutrients from blood vessels
-stratified squamous epithelium
-multiple layers of cells continuously renewed
-mitosis pushes new cells from deep within epidermis to the top
-squams AKA lost cells from surface
-layers of skin=strata
stratum basale single layer of dividing cells, melanocytes (melanin granules) found in nose/footpad
stratum granulosum cells flattened, keratinisation (keratin infiltrates cells) begins, provides protection for extra-weared layers (footpads)
stratum lucidum cells lose nuclei, become clearer
stratum comeum most superficial, cells have no nuclei, dead, fully keratinised and flattened
Dermis:
-Deep layer of the skin
-dense connective tissue
-irregularly arranged collagen and elastic fibres
-generous supply of blood vessels, nerves and sensory nerve endings
-hair follicles, sebaceous glands + sweat glands found here
Hypodermis:
-AKA subcutis/subcuticular later
-layer of loose connective tissue + fat
-contains elastic fibres (flexible skin)
-“scruff” of dogs and cats
Skin
Glands
Sebaceous:
-alveolar/sucular, ducts open to base of hair follicle
-oily substance “sebum” is secreted (waterproofs skin and coat) ~ antiseptic=bacteria
-some modified > pheromones influence behaviours
*Tail=dorsal surface base of tail> individual recognition and identification
*Circumanal=entire circumference of the anus> drain to special sweat glands for individual smell
*Anal=line walls of paired spherical anal sacs, just below the anus> foul-smelling, released in defecation for territorial marking
*Circumoral=lips of cats> territorial marking
*Ceruminous=external ear canal> decrees cerumen
*Meibomian/Tarsal=eyelids> produces tear film
Sweat:
-AKA sudoriferous
-coiled glands in dermis
-active on nose and footpads of cats/dogs
Mammary:
-greatly modified, enlarged sweat glands
-secrete milk for nourishment of young
Hair
-Possession of hair/fur ~ distinctive characteristic of mammals
-Covers all areas except nose and footpads
-Areas such as scrotum and nipples, hair is sparse
-Keratinised structure, produced by hair follicle
Hair shaft>hair root>hair cone>dermal papilla (cyclical)
Hair shaft=within the follicle is the hair root
Dermal papilla=provides blood and nerve supply for growing hair
Development of hair papilla + cone> follicle starts to develop> sebaceous gland develops and developing hair breaks through skin> mature hair follicle with attractor pili muscle
Hair growth cycle:
1) Anagen {maximal hair length, rigorous}
2) Catagen {growth slows, resting, shorten = wear}
3) Telogen {growth stops, club hair recedes, weeks to years = season)
Hair Types:
- Guard~ thick, long, stiff> outer protective coat> waterproofs wool hair> one guard hair per follicle> smooth muscle arrector pili (insulation, visual)
- Wool~ soft undercoat> thinner and shorter hairs> numerous> number varies by season and breed> thermal insulation
- Vibrissae/Tactile~ thicker than guard hairs> protrude beyond coat> grow from follicles within the hypodermis> responsive to mechanical stimuli> found in patches (dog cheeks)
Footpads
-AKA digital pads
-protect underlying joints, shock absorbers (walking/running)
-covered by thick, pigmented, keratinised + hairless epidermis
-surface of pad is roughened by conical papillae, provide traction (dogs)
-pads of cats are smoother
-inside = digital cushion, thickened dermis and fatty vascular tissue > absorbs impact of foot hitting the ground
-sweat glands on surface
Dogs and cats have 7 pads on each forepaw
*5 digital pads ~ one for each interphalangeal joint
*Metacarpal pad ~ phalangeal-metacarpal joint (heart shaped for dogs, circular for cats)
*Carpal pad ~ stop pad, distal to the carpal pads and protects at high speeds
Problems:
Abrasions and sores (hard/rough surfaces, walking for a long time)
Lodged foreign bodies
Cuts and punctures (step on sharp objects)
Burns (hot surfaces, hot weather)
Chilblains/Frostbite (inflammation of blood vessels)
Damage to paws (bones) due to impact and trauma
Ingrowth claws/Overlong claws
Abnormal claws
Claws
- composed of modified keratinised epidermis
- form the horny outer layer covering of distal/3rd phalanx of each digit (incl. few claw > cover unfurl process)
- protect during walking, weight bearing and gripping
- dog claws (thick and strong)
- cat claws (fine, sharp = offence) + retracted at rest (pockets of skin with elastic ligaments ~ run from 2nd and 3rd phalanges) > unsheathed when digital flexor muscle overcomes tension
- claws grow from the coronary border, under claw fold
- 2 hard, laterally compressed walls
- ventral groove filled with softer horn (sole)
- vascular dermis (AKA quick) lies at the base of the claw
