Skin - Integumentary and Appendages
Skin is the largest organ in the body
Combining forms for skin:
a. cutane
b. derm
c. dermat
d. derma
I. Functions of the skin:
a. Protective membrane
b. Glands which produce secretions
c. Nerve fibers for sensation
d. Maintain body temperature
II. Structure of the skin
A. Epidermis (epi- above, dermis - skin)- outer membrane
 Takes 21 days for normal mitosis of an animal’s skin
 Animals have thinner epidermis layers than humans
 Made up of squamous epithelium (flat, platelike cells)
 Lacks major blood vessels - avascular
 Depends on capillaries for nourishment
 Melanocytes - cells that contain Melanin (Black pigment)
 Keratin (Kerat – horny) is a protein that provides skin with its waterproofing
properties
B. Dermis
 Composed of blood, lymph vessels, nerve
 Fibroblasts - fiber producing cells for repair.
 Histocytes (macrophages) - phagocytic cells
 Mast cells - cells that produce histamine and heparin
 Arrector pili - muscles attached to hair follicles to stiffen the hair - “raising the
hackles”
 Sebaceous gland - oil gland
 Sweat glands
 Follicles
C. Subcutaneous Layer
Located under the dermis and is composed of connective tissue - fat or lipid or
adipose tissue.
III. Hair
Rodlike fibers made of dead protein cells filled with keratin.
A. Types of hair
1. Fur - short, fine, soft hair
2. Guard hairs - long, straight, stiff hairs that form the outer coat; primary hair or
top coat.
3. Secondary Hairs - finer, softer, and wavy hair; undercoat.
4. Tactile Hair - long, brittle, extremely sensitive hairs usually located on the face
B. Hair development
1. Simple - guard hairs that grow from separate follicular openings, as in cattle
2. Compound - multiple guard hairs that grow from a single follicle, as in dogs.
C. Color of hair
3 primary pigments - black, brown, yellow
Gray hair - loss of pigment
White hair - absence of pigment and presence of air in the hair shaft
D. Shedding/Molting
Controlled by temperature, hormones, photoperiod, and nutrition
IV. Nails, Horns, Hooves
Quick - blood supply for nails/claws
Coronary band (Coronet) - growth of the hoof
Chestnuts/Ergots - vestigal pads in horses. Chestnuts are located on the medial surface of
the leg above the knee or hock. Chestnuts correspond to carpal pads in the dog. Ergots
are located in the tuft of hair on the fetlock joint. Ergots correspond to metacarpal and
metarsal pads in the dog.
Horn - permanent structure that grows continuously after birth. Breeds that are naturally
hornless are called polled.
Antler - not permanent and are shed and regrown annually. Antlers are initially covered
with skin called velvet. When the animal rubs off the velvet, the bone is exposed, the
antlers lose their blood supply and are shed off.
V. Feathers
A. Types of feathers
1. Contour - covers a bird’s body and constitutes the flight feathers
a. Remigies - wing flight feathers
b. Rectricies - tail flight feathers
2. Semiplume - found under contour feathers; provides insulation; help with
buoyancy in water birds.
3. Down - soft feathers located near the skin to provide insulation
4. Filoplume - located on the neck and head
5. Bristles - around the eyes, nares, mouth; provides a sensory response
B. Wing trims
Larger birds - trim the first 4 primary remigies
Smaller birds - trim the first 5-6 primary remigies
V. Pathology
1. Abrasion - injury to superficial skin layers
2. Abscess - collection of pus
3. Acne - plugged sebaceous glands. Cats are prone to feline acne. Scrub the area with
iodine and treat with benzoyl peroxide.
4. Hot spots (Pyoderma) - occurs due to intense scratching or licking due to allergy or
inflammation
5. Alopecia - hair loss
6. Cellulitis - inflammation of connective tissue
7. Contusion - injury that does not break the skin; redness and inflammation
8. Dermatitis - inflammation of the skin
9. Discoid lupus erythematosus (Collie nose or solar dermatitis) -canine autoimmune
disease. The bridge of the nose exhibits depigmentation, erythema, scaling and erosions.
Commonly seen in Collies, German Shepherds, Huskies, Labs, and Sheep dogs.
10. Ecchymosis (bruise) - bleeding into the skin from a broken blood vessel.
12. Eczema - general term for inflammatory skin disease; crusts, scabs, vesicles, papules
13. Fissure - cracklike sore
14. Fistula - abnormal passage from an internal organ to the body surface
Perianal fistula
15. Gangrene - necrotic tissue.
16. Granuloma (Proud Flesh) - scar tissue
17. Lipoma - fatty tumor
18. Melanoma - tumor of the pigment cell
.
19. Papule - small, raised skin lesion
20. Pemhigus - immune mediated skin disease; ulcers, blisters; most common in Akitas,
Chows, Dobies, German Shepherds, Labs, Newfies
21. Petechie - small, pinpoint hemorrhages.
22. Sebaceous cyst - closed sac of yellow fatty material.
23. Ulcer - open sore
Decubital ulcer - (bed sore) erosions of skin as a result of prolonged pressure
24. Urticaria - hives
25. Vesicle - blister; fluid filled sac
26. Erythema - redness of the skin indicating inflammation
27. Pruritus - itching
28. Schnauzer Comedo Syndrome
Hereditary disorder of follicular Keratinization
Small crust on the back
Treatment - benzoyl peroxide shampoo
29. Demodectic Mange - “cigar shape mite”
Mites live within the hair follicle
Signs: patches of alopecia, variable erythema, secondary bacterial infection; head
and limbs are affected
Treatment - Benzoyl peroxide shampoo
Zoonotic
30. Sarcoptic Mange - burrowing mite
Mite has a short life in the environment
Signs: itching, crusted area around the ears, elbows, hocks, inguinal area
Treatment: Mitaban, Dips
Not zoonotic
31. Cheyletiella - Walking Dandruff
Affects dogs, cats and rabbits. Mites feed on the skin scales and can live up to 10 days in
the environment.
Signs: pruritic skin
Dx: scotch tape, skin scraping
Tx: ivermectin
33. Cuterebriasis - most common in rabbits
Botfly lays the eggs in the soil or feces, the larvae hatch and penetrate the skin, mature to
the pupal stage beneath the skin. There will be a small air hole in the skin for the pupal to
breath. To remove the pupal, carefully extract it without crushing it or the rabbit will die
from the toxin being released.
34. Dermatophytosis - Ringworm
Zoonotic fungus commonly seen in cats
Signs: alopecia, scaling, inflamed rash or lump
Dx: woods lamp, signs, DTM media
Tx: Antifungal cream or shampoo
35. Lick granuloma
Causes are usually boredom or irritation to the area.
Signs: the animal will lick the area constantly causing alopecia, inflammation, open sores.
36. Warts