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
Matrix is
rapidly dividing epithelial cells covering the papilla
Nourished by vessels below
As cells divide, they push older cells up become keratinized & die become hair
Root hair plexus
Web of sensory nerve endings around the root
Makes hair sensitive to touch
Compound follicles
Multiple hair strands, each with its own follicle, can emerge from a single pore
Three follicles group to emerge from same epidermal fold in dogs
Can contain a mixture of primary and secondary follicles (see later)
Three stages of growth in hair
Anagen: growth
Catagen: transition
Telogen: resting
During telogen what happens
During telogen hair bulb separates from the dermis
Hair falls out or is pushed out when new hair growth starts
‘Shedding’ the coat is technically called telogen effluvium
Can occur seasonally (photoperiod), due to disease, or through hormonal changes (such as after parturition in bitches (blowing the coat)
telogen effluvium
shedding the coat
Hair colour is determined by
Pigment in cortex and medulla of hair strand
Melanin produced in base of hair follicle
Melanin transferred to cortical and medullary cells of hair strand
Different colors
Quantity of melanin
Type of melanin
Orange type
Black/brown type
No melanin = white
Melanin production decreases with age
Primary hair
guard hairs
Straight or arched; thicker and longer than secondary hairs
Secondary hair
Softer and shorter than primary hairs
Predominant type of hair in wool type coats
Wool breeds have many secondary hair follicles
Compound hair follicles often have
Long primary guard hair
Surrounded by soft wool hairs
Tactile hair
Wool breeds have many secondary hair follicles
Secondary hair is often waxy (lanolin)
Makes it waterproof
Used in skin ointments
Arrector Pili Muscle
Small, smooth muscle
Attached to each hair follicle
Innervated by sympathetic nervous system
Contraction pulls the hair erect
Sweat glands are and do what
Sudoriferous Glands
Produce watery, transparent liquid
Help cool body through evaporation
Found over entire body
Only horse produces profuse sweat
Two types of sweat glands
Eccrine: empty onto surface of skin
Apocrine: empty into hair follicles
Sweat glands are and what do they do
Located in dermis
Simple or complex alveolar structures
Duct empties into hair follicle or directly onto skin
Lips, labia vulvae, penis, prepuce, anus, eyelid, ear canal (ear wax)
Produce sebum
Oily, lipid substance
Manufactured and stored by sebaceous glands
Sebum forced through duct into hair follicle
Sebum does what and is also called
Sebum coats base of hair and surrounding skin
Traps moisture
Keeps skin and hair soft, pliant, waterproof
Reduces risk of infection
Sheep sebum is called lanolin
Sebaceous glands
Secretion of sebum is hormone sensitive
Increased production of sebum at puberty, sebum binds dead skin cells, blocks duct opening.
Ducts swell and may rupture – releases bacteria into epidermis and dermis,inflammation and abscess
Tail and chin glands
Oval region at dorsal base of tails of dogs and cats, contain:
Large sebaceous glands
Coarse, oily hairs
May have different color
Assist animals in identification of one another
More noticeable in males
Called Stud Tail in cats
Also found on chin and lips of cats
May develop into cysts
Anal sacs
Reservoir for malodorous secretions, similar to those from musk glands
Lined with sebaceous and apocrine glands
Contents are expressed at:
Defecation: marks territory
When animal is frightened
Location in cats and dogs
Connected by single small duct to lateral margin of anus
Can become blocked / infected
Anal sac disease is
May become impacted or infected – ‘scooting’
Pain and discomfort on sitting
Licking and biting at anal area
Painful defecation
If severe, may swell and rupture and drain pus
May be a sign of allergies
Treatment for anal sac disease
Express with digital pressure
Keep your mouth closed
Flush with catheter and warm water +/- disinfecting soap
May surgically remove
Ruminant hooves
Ruminants have 4 hooves per foot – each covers a digit, but only 2 digits (3rd and 4th) per foot are weight- bearing
Bovine hoof
Weight bearing hooves are called medial and lateral claw
Hoof wall
Is equivalent to our fingernail
Divided into toe, quarters (medial and lateral), and heel regions
Thickest at the toe and thinnest at the heel.
Hoof wall cross sections
Have tiny vertical lines running from coronary band to ground - called horn tubes
May have horizontal rings or ridges around hoof – represent different periods of growth due to changes in nutrition or founder
Grows continuously from the (corium of the) coronary band down
Hoof walls are flexible and expand as weight is born on hoof
Corium
like a modified dermis
The underlying tissue which is sensitive and vascular.
Firmly attached to periosteum of distal phalanx – links bone to hoof wall
Lots of blood vessels and nerves
Divided into coronary corium (beneath coronary band), perioplic corium (beneath periople), laminar (wall) corium, sole corium (on the sole of the foot), and corium of the frog (above/behind the frog)
Periople or Perioptic corium
Narrow region approximately 2-3 cm at proximal border of hoof
Epidermal cells here produce the external layer of the hoof wall
Corresponds to the cuticle of the fingernail
Waterproof and pigmented
Coronet or Coronary corium
Wider band distal to periople
Cells here produce the middle layer of the hoof wall
The hoof grows from the coronary band downward
Growth of the hoof is continuous
Without trimming the hoof can become so long that it curls upward
How the corium and epidermis (hoof wall) attach to each other
Hoof and corium form laminae, which interlock
Connect the hoof wall to the corium, which is bound to P3
Laminae permit hoof wall to grow distally by sliding over each other
Dermal laminae are sensitive
Sole of the horse hoof
Bottom (plantar or palmar) surface of the hoof
Protects from injury
Concave – not primary weight-bearing area
Improves foothold
No nerves or vessels superficially
White line – indicates junction of the sole and hoof wall
Frog of the horse hoof as and functions to
Triangular shaped structure with a central sulcus or cleft
Below the frog is a thick pad of fat and fibrous tissue, called the digital cushion
Functions
Cushion at the heel of the foot
Reduces slipping
Helps to mechanically pump blood back up the leg from the corium during weight-bearing (see below)
Remember to firmly pick out the sulci of the frog when you clean a horse’s foot
Shoeing of a horse does what
Shoeing a horse prevents excessive expansion of the hoof when the animal carries weight
Also improves traction and creates a barrier between the ground and hoof – protects from injuries
Usually combined with trimming
What happens to the horse hoof as they walk to allow blood flow
Frog and digital cushion are flattened and widened during weight-bearing
This puts pressure on the walls and bars and collateral cartilages causing the walls to spread at the heels
Pressure forces blood out of the vascular bed of the foot
Since the blood is forced out against some resistance, this provides additional absorption of concussion
Cartilages of the equine hoof do what
Lateral or collateral cartilages are a pair of cartilage structures attached to the angles of P3 and extending into the area of the heel proximal to the coronary band of the hoof
Bones of the equine hoof
Distal part of the middle phalanx, distal sesamoid bone – “navicular”, and the distal phalanx – “coffin bone”
The distal (3rd) phalanx has layers of sensitive laminar corium which interdigitate with the laminae of the hoof
Laminitis in equine is
Inflammation of the laminae attaching hoof wall to corium
Laminae swells
Swelling is trapped inside the wall of the hoof
Inhibits blood flow to corium due to compression
Corium may degenerate
Attachment between wall and corium is lost
Pedal bone can rotate or sink within the hoof
Puts pressure on sole, may perforate sole
Laminitis is caused by
Overload
Inflammatory
Metabolic diseases
Overload in laminitis
reduced weight bearing on a limb (trauma or surgery) causes excessive weight bearing in other limbs
Inflammatory in laminitis
A major cause is dietary
Sudden increase in the amount of grain (intentionally or accidentally) or rapidly growing fresh spring grass ingested.
Grain is full of starch and some will reach the large intestine. Grass is full of fructose polymers which cannot be digested in SI and pass intact to LI
As a result there is bacterial overgrowth and fermentation in the large intestine.
Toxins are produced. These are absorbed and produce inflammation of the hoof wall
Equine metabolic syndrome effect on laminitis
Insulin dysregulation, abnormal fat deposition, difficulty losing weight.
“Cresty” neck horses and ponies
PPID effect on laminitis
Pituitary pars intermedia dysfunction (PPID)
Equine Cushings
Cortisol excess causes delayed shedding (results in longhair coats), PU/PD, insulin dysregulation
Treatment for laminitis
Treatment – pain relief and anti-inflammatory meds
Ice – prevents breakdown of laminae
Some changes can be corrected or improved with corrective shoeing and trimming, feed, and management (takes months)
Euthanasia if rotation has occurred
Effects of laminitis
Laminitis is extremely painful
Usually front feet are affected (can be all 4)
Horses stand with front feet out and hind limbs under body
If all 4 feet affected, all feet are tucked together
Horse may lay down a lot and be unwilling to stand
Hooves feel warm with increased digital pulses
Sole may sink (flatten)
P3 may poke through sole
Hoof wall develops ridges and curls up at toe
Prevention of laminitis
Limit high CHO feeds
Especially ponies in Spring
Often occurs after sudden introduction to lush pasture grazing or high CHO foods like grain, molasses, and corn
Severe illness (retained placenta with metritis) can also be complicated by laminitis
Monitor feet carefully and treat at first signs
Sand cracks are and are caused by
Vertical cracks in hoof
Named for region of occurrence - toe, heel, quarter cracks
Cause
If begin at solar border result of improper or no trimming
If begin at coronary band results from defect in hoof formation
Excessive drying of hoof predisposes to the condition
Thrush in horses
Degenerative condition of the frog
Associated with filth and various micro-organisms.
Characterized by black, necrotic, foul smelling material in the affected area
Contracted foot/heels in equine
Foot is narrower than normal
May be caused by lack of frog pressure and often occurs in horses improperly shod
Front more commonly affected than back and can be severe enough to cause lameness known as hoofbound
Contracted heels the heels of affected horses are drawn in, the bars are almost parallel and the frog is much reduced in size.
Also called contracted hoof or contracted foot.
Navicular disease
Chronic degenerative condition of navicular bone
Seen in older horses
Primarily a disease of the forefeet
Trauma of high impact weight bearing (racing) and defective shoeing are contributory factors
Often begins with loss of cartilage and inflammation of the bursa between the navicular bone and the deep digital flexor tendon
Navicular disease is a common cause of “heel pain” lameness in horses
Bovine foot rot
Proliferative inflammation of interdigital space, coronary region and P3.
Several micro-organisms cause foot rot
Signs: Foul smell, redness, swelling, redness, discharge from damaged interdigital skin
Very responsive to antibiotics
Interdigital Dermatitis (Slurry Heal)
Infection of the heel bulb and interdigital skin
Rarely lame
Treated with topical disinfectants such as coppertox.
Wear gloves!
Interdigital Fibroma
Proliferation of tissue of interdigital cleft
Often associated with foot rot and interdigital dermatitis
Mass of connective tissue projecting down and between claws
Walking becomes painful as corn increases in size
Vertical fissures in bovine
usually animal is suffering from overgrown hooves resulting in abnormal weight bearing, may also be laminitic
Incidence increases during dry weather which causes hoof wall to become hard and lose its elasticity
Horizontal fissures (thimbling) in bovines is
usually occur in mature dairy cattle following attack of laminitis
Usually all 8 claws are affected
Laminitis in bovine is
Most foot lameness of cattle is directly or indirectly related to laminitis
Major cause - ingestion of excessive amounts of grain.
Only mildly painful in cattle.
The integrity of the lamina and hoof wall and sole are all compromised when laminitis occurs
Overgrown and malformed hooves result, haemorrhage in the sole, possibly necrotic toe lesions
Horn is and composed of
Boney outgrowth with epidermal covering
Similar to hoof - keratin tubules bound to periosteum of underlying bony core by a corium
Starts as an epithelial horn bud. Grows out as a solid structure that becomes hollowed out by about 6 months of age
Adult animals have hollow horn that communicates with the frontal sinus
Male and female animals may have horns
Pronghorn antelope are only species to shed horn annually – rest are permanent and grow continuously through life
Polled = no horns in a species that was historically horned, though can have remnants
Antler is and process of shedding
Tend to be only in males
Shed annually
Bony growth that is nourished by the velvet on the outside
Once grown, a connective tissue ring forms like a tourniquet around the base of the antler to cause velvet slough
Antler hardens
Late fall/winter the bony base connecting antler to skull weakens and antler falls off
Antler harvest methods used to get animal to cooperate
PAINFUL!!!
Many methods used to get animals to cooperate
Local anesthetic blocks
Tourniquet
Restraint (physical, chemical)
