Skin - Integumentary and Appendages

Skin is the largest organ in the body

Combining forms for skin:

a. cutaneb. dermc. dermatd. derma

I. Functions of the skin:a. Protective membraneb. Glands which produce secretionsc. Nerve fibers for sensationd. Maintain body temperature

II. Structure of the skinA. 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 LayerLocated under the dermis and is composed of connective tissue - fat or lipid or adipose tissue.

III. HairRodlike fibers made of dead protein cells filled with keratin.

A. Types of hair1. Fur - short, fine, soft hair2. 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 development1. Simple - guard hairs that grow from separate follicular openings, as in cattle2. Compound - multiple guard hairs that grow from a single follicle, as in dogs.

C. Color of hair3 primary pigments - black, brown, yellowGray hair - loss of pigmentWhite hair - absence of pigment and presence of air in the hair shaft

D. Shedding/MoltingControlled 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. FeathersA. Types of feathers

1. Contour - covers a bird’s body and constitutes the flight feathersa. Remigies - wing flight feathersb. 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 insulation4. Filoplume - located on the neck and head5. Bristles - around the eyes, nares, mouth; provides a sensory response

B. Wing trimsLarger birds - trim the first 4 primary remigiesSmaller birds - trim the first 5-6 primary remigies

V. Pathology1. 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 soreDecubital 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 SyndromeHereditary disorder of follicular KeratinizationSmall crust on the backTreatment - 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 affectedTreatment - Benzoyl peroxide shampooZoonotic

30. Sarcoptic Mange - burrowing miteMite has a short life in the environmentSigns: itching, crusted area around the ears, elbows, hocks, inguinal areaTreatment: Mitaban, DipsNot zoonotic

31. Cheyletiella - Walking DandruffAffects dogs, cats and rabbits. Mites feed on the skin scales and can live up to 10 days in the environment.Signs: pruritic skinDx: scotch tape, skin scraping Tx: ivermectin

33. Cuterebriasis - most common in rabbitsBotfly 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 - RingwormZoonotic fungus commonly seen in catsSigns: alopecia, scaling, inflamed rash or lumpDx: woods lamp, signs, DTM mediaTx: Antifungal cream or shampoo

35. Lick granulomaCauses are usually boredom or irritation to the area.Signs: the animal will lick the area constantly causing alopecia, inflammation, open

sores.

36. Warts