Integument and related structures Flashcards
Special features of the integument
Pigmentation
Paw pads
Ergots and chestnuts
Planum nasale
Cutaneous pouches in sheep
Functions of the skin
Covers and protects
Prevents desiccation
Reduces threat of injury
Assists in maintenance of normal body temperature
Excretes water, salt, organic wastes
Receives and conveys sensory information
Synthesizes vitamin D
Stores nutrients
Skin maintains a suitable internal environment for other body tissues and organs by preventing:
Loss of water and electrolytes from the body
Access of external chemicals, micro-organisms and toxins to the body
Epidermis
Above the basement membrane
Composed of keratinized stratified squamous epithelial cells
No blood vessels
Dermis
Tough layer below
Composed of dense irregular connective tissue
Contains blood vessels
Below is the hypodermis, or subcutaneous layer
Primarily adipose tissue (thermoinsulation and protection against injury)
Keratinocyte
Keratin gives skin resiliency and strength
Helps make it waterproof
Majority of skin cells
Produced at basement membrane
Become keratinized, loose nucleus, die (keratinization)
Sloughed at surface
Melanocyte
Produces melanin pigment
Processes extend up through the epidermis
Protects against UV light
Langerhans cell
Phagocytizes microinvaders
Merkel cell
Associated with sensory nerve endings
5 layers of thick skin
Stratum corneum = horny layer
Stratum lucidum = clear layer
Stratum granulosum = granular layer
Stratum spinosum = spiny layer
Stratum germinativum = stratum basale = basal layer
Layers of thin skin
Stratum corneum
Stratum spinosum
Stratum basale
Thin skin epidermis description
Scalelike folds on skin surface
Hair grows out from folds
Tactile elevations = epidermal papillae
A tactile hairs = tylotrich hair grows from each papillae
Sense of touch
Dermis composed of what CT
Highly fibrous; dense irregular connective tissue
Collagen, elastic, reticular fibers
Provides strength
Can be tanned to make leather
Component of dermis
Hair follicles, nerve endings, glands, smooth muscle, blood vessels, lymphatic channels, fibroblasts, adipocytes, macrophages
Papillary layer of dermis
Thin, superficial layer
Lies just below epidermis
Dermal papillae
Looping blood vessels
Nerve endings (pain) and Meissner’s corpuscles (touch)
Hypodermis description
Thick layer, below dermis
Allows skin to move freely over underlying structures
Loose layer of areolar tissue containing:
Fibers continuous with dermis
Adipose, blood and lymphatic vessels, nerves
Pacinian corpuscles
Special type of touch receptor for heavy pressure
Reticular layer of the dermis
Majority of dermis
Indistinct boundary between papillary layer
Parallel bundles of collagen fibers
Arranged parallel to tension
Skin incisions are made along these lines
Minimizes wound gaping
Speeds healing
Dermal folds or flexure lines e.g. at joints
Pigmentation of the skin
All animals have melanocytes
The amount and type (orange/black) of melanin produced is variable
Albinos produce no melanin
Pigment is released in vesicles which are taken up by keratinocytes to give them color
Coat color is the result of the presence or absence of melanin granules in extensions of melanocytes, keratinocytes and hair.
Sun exposure increases melanin synthesis in people
Functions of the paw pad
Shock absorbers for the feet
Insulation against heat and cold
Protection against rough surfaces
Foundation of he paw pad
A thick layer of fat and CT
Covered by thick epithelium
Layer of paw pads
Have the thickest and toughest skin on the body – has all 5 layers
Thick surface layer (stratum corneum) that is rough and in the form of conical papillae
Worn almost smooth on the walking surface
Paw pad glands
Has exocrine sweat glands
The only site where most domestic animals sweat
Except horses!
Sites on the paw pad include
Carpal: on the caudal surface of the carpus, at the accessory bone
Metacarpal/Metatarsal: main weight bearing foot pad
Digital: one on each toe
Ergots and chestnuts are
Dark, horny structures on legs of equine family
Thought to be vestiges of digits
Chestnuts are located
Medial on each leg at carpus and tarsus
Ergots are located
Buried in caudal hairs of fetlock
Planum nasale
Dorsum of nose in cats, pigs, sheep, dogs
Composed of polygonal plates in dogs
Planum nasolabial
Extends to lips
Muzzle of cows
Hairless in cattle
Planum Nasale/Nasolabiale
Usually pigmented
Aglandular in SA, glandular in sheep and cattle
Why do cows lick there nose
Sick cows may stop licking their nose and drool clear mucous from their nose
Not necessarily a sign of respiratory disease
Cutaneous pouches in sheep are and location
Infoldings of skin
Contain fine hair, sebaceous and oil glands
Three locations
Infraorbital
Interdigital
Inguinal
Fatty yellow secretion dries and sticks to skin
PRISH in skin
Pain
Itching (licking/chewing/scratching) (pruritus)
Reddening
Immobility (Loss of function)
Alopecia (loss of hair)
Thickening (lichenification)
Wrinkling
Pigmentation (melanosis)
Swelling: Edema
Heat
Functions of hair
Maintenance of body temperature
Traps air
Dark colors absorb light
Protection via camouflage
Hair folilicle
Shaft: part of hair visible above skin
Root: part of hair below skin
Hair follicle: invagination of the epidermis into dermis or hypodermis
Hair shaft three layers
Medulla: core of the hair
Cortex: hard keratin – thickest layer
Cuticle: thin layer of cells on the surface of the hair arranged in shingle-like layers
Hair bulb is
deepest part of hair follicle – expanded, knob-like, hollow area
Papilla is
mound of dermal cells at the base of the bulb