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Definition
| Inflammation of the dermis and epidermis caused by tiny mites that live on or in the skin. |
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Definition
| Inflammation of the dermis and epidermis |
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| Deep scratches within the skin, due to animal rubbing and scratching themselves |
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| Deep scratches within the skin, due to animal rubbing and scratching themselves |
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| Bacterial infections of the skin |
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| Describe Demodex and exam to find them |
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Definition
| These are long, thin mites with short stubby legs, found in the hair follicle and sebaceous glands. These are found by performing a skin scrape. |
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| Describe Sarcoptes and which exam to find them |
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Definition
| These mites are round and like to bury in the excoriations of the skin. Drawn to areas relatively hairless. Also known as scabies and found by doing a skin scrape. |
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| These mites are mainly found on cats, rats and rabbits. They look and behave like Sarcoptes, but smaller. Usually begin on the ears, then spreads to paws and hind feet. |
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| Why is skin important? Name 5 important functions of the skin. |
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Definition
Skin is important because it is one of the largest and most extensive organ systems in the body. It involves every inch of the external animal and includes hair, hooves, horns, claws, and various skin-related glands.
1. Skin covers and protects underlying structures.
2. By forming a critical barrier between the delicate inner workings of the body and the harsh elements of the external world, skin prevents desiccation and reduces the threat of injury.
3. Skin assists in the maintenance of normal body temperature.
4. Skin excretes water, salt, and organic wastes.
5. Skin is an important sensory organ that takes in information from the environment through touch and pressure and conveys this input to regions of the central nervous system.
6. Skin is engaged in the synthesis of vitamin D and the storage of nutrients. |
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| What is keratinization and why is it an important process? |
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Definition
| The majority of cells in the epidermis are keratinocytes. Keratinocytes located along the basement membrane are well nourished by the blood supply of the underlying dermis, therefore these cells can grow and divide. When new daughter cells are produced, they push older cells away from the life-sustaining nutrients of the dermis toward the outer layers of the epidermis. As older cells travel from the basal to the superficial layers, they undergo profound changes: they fill with keratohyaline granules; lose their nuclei, cytosol, and organelles; and ultimately become lifeless sheets of keratin. This process is called keratinization and enables millions of dead cells to rub off or "exfoliate" daily at no expense to the animal's health. Keratinization is important because keratin is a tough, fibrous, waterproof protein that gives skin its resiliency and strength. |
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| List all five layers of the epidermis. What is happening in each layer? |
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Definition
From the innermost layer outward:
1. The stratum germinativum, also known as the stratum basale (basal layer). For the most part, this layer consists of a single row of keratinocytes which are firmly attached to the epithelial basement membrane and actively engaged in cell division. New daughter cells move from the stratum basale to sequentially more superficial layers as they mature. In this way, they replace epithelial cells that have exfoliated at the skin’s surface. Merkel cells and melanocytes are found in this layer.
2. The stratum spinosum (the prickle-cell layer). The stratum spinosum (spiny layer) is so named because when the cells of this epidermal layer are fixed for histological exam, they contract into speculated masses that resemble sea urchins. It contains several layers of cells that are held together by desmosomes.
3. The stratum granulosum (granular layer) is the middle layer of skin. Composed of two to four layers of flattened, diamond-shaped keratinocytes, the stratum granulosum is the highest level of the epidermis where living cells can be found. The cytoplasm of these cells begins to fill with keratohyalin and lamellated granules, which in turn leads to the dramatic degeneration of the nucleus and other organelles. Without these vital parts, the cell quickly dies. The lamellar granules contain waterproofing glycolipids and are transported to the periphery of the cell, where their contents are discharged into the extracellular space. These glycolipids play an important role in waterproofing the skin and slowing water loss across the epidermis.
4. The stratum lucidum (clear layer) is found only in very thick skin. Most skin therefore lacks this layer. Microscopically, the stratum lucidum appears as a translucent layer composed of a few rows of flattened dead cells. In this and the outermost epidermal layer, the sticky contents of the keratogranules combine with intracellular tonofilaments to form keratin fibrils.
5. The stratum corneum (horny layer) is the outermost layer and dominates the epidermis. It constitutes up to three quarters of the total epidermal thickness and is composed of 20 to 30 rows of keratinocytes. On sagittal section, the cells have a paper-thin, almost two-dimensionality, yet when viewed from above, they appear hexagonal. These are really only the remnants of keratinocytes, because the actual cell died in the stratum granulosum. Sometimes called horny or cornified cells, we commonly call them dandruff and recognize them as the flakes that occasionally drop on our shoulders. |
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| How is the skin of hairy animals different from that of humans? |
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Definition
Skin covered with fur usually consists of three epidermal layers rather than five. These layers are the stratum basale, stratum spinosum, and stratum corneum. The stratum granulosum and stratum lucidum are generally missing. A few regions of five-layered epidermis can be found in furry mammals, but these are usually seen in places where the keratinization process has slowed and the skin is very thick.
The surface of “hairy skin” is covered in scalelike folds. Hair emerges from underneath the scales and is directed away from the opening of the hair follicle. In dogs the hair is organized in clusters of three follicles per scale. Periodically throughout the surface of the epidermis a knoblike elevation can be seen. This is called a tactile elevation, or epidermal papilla. Each tactile elevation is usually associated with a tactile hair. These special hairs are called tylotrich hairs, and they are important in the perception of touch. |
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| How is dermis different from epidermis? |
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Definition
| Unlike the epidermis, which is primarily cellular, the dermis is highly fibrous. It is composed of dense irregular connective tissue that contains collagen, elastic, and reticular fibers. Hair follicles, nerve endings, glands, smooth muscle, blood vessels, and lymphatics are all found in the dermis as well, creating a rich and interesting tissue community. Fibroblasts, adipocytes, and macrophages also are present and represent the most commonly found cellular elements. The dermis is a tough layer that binds the superficial epidermis to the underlying tissues. It represents the "hide" of the animal and is used to make leather. |
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| What causes pigmentation of skin? |
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Definition
| Pigmentation is caused by the presence or absence of melanin granules in the arm-like extension of the melanocytes. Grossly, no pigmentation is apparent if the granules are concentrated around the nucleus in the cell body of the melanocyte. As they move into the cellular "arms" and into the surrounding tissue, pigmentation becomes grossly apparent. The more granules in the arms of the melanocyte and surrounding tissue, the darker the pigmentation. |
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Term
| How are paw pads and planum nasale different from other regions of skin? |
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Definition
Digital pads are formed by thick layers of fat and connective tissue that bear the weight of the animal. The pad’s outer surface is the toughest and thickest skin in the body. It is often pigmented and is composed of all five epidermal layers. Of these five layers, the outermost epidermal layer, the stratum corneum, is thicker than all the others combined. This tough outer skin together with insulating fat forms a protective barrier against abrasion and thermal variances, enabling the animal to walk on rough surfaces, hot roads, and cold snow. The surface of the pad feels rough, and an uneven surface is visible to the naked eye.
The pad is composed of exocrine sweat glands and lamellar corpuscles. Histologically, the ducts from these sweat glands can be seen passing through the dermis to the stratum basale of the epidermis. Their glandular excretion is then excreted onto the surface of the pad.
The planum nasale is usually pigmented and appears to be a tough, thick region of integument histologically; however, the planum nasale in the dog is composed of only three epidermal layers with the stratum lucidum and stratum granulosum absent. The outermost layer, the stratum corneum, is composed of only four to eight cell layers, surprisingly thin considering the exposed location of the nose and its heavy use, particularly in the dog. The epidermal surface of the planum nasale is divided by deep surface grooves giving it the appearance of being composed of multiple plaques. As with other regions of the skin, the dermis and epidermis interdigitate to form an irregular line of attachment that includes dermal papillae. Although often moist from nasal secretions and licking, the planum nasale in the dog contains no glands in the epidermis or dermis. However, in the sheep, pig, and cow, tubular glands are found. |
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Term
| List the functions of hair. |
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Definition
| Hair has an important role in maintaining body temperature by trapping insulating layer of air. If dark, will further assist in warming the animal by absorbing light. The color helps in camouflaging the animal. |
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| List the 3 phases or cycles of hair growth and what occurs during each stage. |
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Definition
Anagen phase – hair is produced – dead, keratinized cells epithelial cells push up and away from the dermal papilla and are organized into the layers that make up the hair shaft and root. As more cells are added at the base of the root, the hair lengthens
Telogen phase – when max hair length is achieved, the hair stops growing , the hair follicle shortens, and the hair is held in a resting phase. This quiescent period can last from weeks to years depending on the location, type of hair, and species involved
Catagen phase – the period of transition between the anagen and telogen phase |
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| What factors influence hair growth? |
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Definition
| Genetics and environment. |
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Term
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Definition
| Single, long hair also known as primary hair, or cover hair, that is usually surrounded by shorter hairs(satellite) |
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| What tissue does hair originate from? |
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Definition
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| Define sinus hairs and list their function. |
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Definition
| Also called tactile hair, these are used as probes and feelers. Commonly known as whiskers. It is called sinus hairs due to the presence of a large blood sinus. |
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Term
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Definition
| A small, smooth muscle that is attached to each hair follicle and is innervated by the sympathetic nervous system. When frightened or cold, this will make the animals hair stand up beyond the normal implantation angle. |
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Term
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Definition
| Deepest part of the hair follicle, located in the dermis and provides the material for hair production |
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Definition
| Wall of the hair follicle composed of three layers - internal epithelial root sheath, out epithelial root sheath, and dermal or connective tissue root sheath. Houses the root hair plexus. |
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Definition
| A web of sensory nerve endings that envelop the root, making it an important touch receptor when the hair is bent. |
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Definition
| When the hair on the back goes up. |
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Definition
| "blowing the coat", or when a large percentage of total hair volume is lost. |
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Definition
| Also called secondary hairs, these are softer and shorter than primary hairs. They are generally wavy or bristled in dogs and are the predominant hair type in species with wool-type coats. |
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Definition
| White, semiliquid mixture of an oily lipid substance composed of glycerides and free fatty acids, and cellular debris. Is ruptured out of the sebaceous glands. Functions as a trap for moisture to keep the skin from drying, and being somewhat waterproof. Also possesses some antibacterial and anti-fungal properties, which reduces risk of infection. |
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| Why does hair turn gray and then white as animals age? |
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Definition
| As animals age, melanin production decreases, and the hair begins to turn gray. White hair is formed when the cortex loses its pigment entirely and the medulla becomes completely filled with air. |
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| How does hair form and grow? |
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Definition
Hair is anchored by the hair follicle. The follicle is an invagination of the epidermis that extends from the skin surface to the dermis or, occasionally, the hypodermis. The deepest part of the hair follicle expands to form a hair bulb. At the base of the bulb is a mound of dermal cells called the papilla. The papilla is covered with rapidly dividing epithelial cells called the matrix. These cells are nourished by blood flow from vessels in the underlying papilla, which stimulates much cell division and growth. As cells divide, older cells are pushed upward into the follicle tunnel away from the papilla. These cells become keratinized, and as they lose contact with the nutrition provided by the papilla, they die and become part of the developing hair. In this way, hair is constructed from dead epithelial cells.
Hair is formed in three concentric layers. The innermost layer (and central core) is called the medulla. It is composed of two to three layers of loosely arranged cells that are separated by spaces filled with liquid or air. The cells themselves contain flexible, soft keratin similar to that found in the stratum corneum of the epidermis. Surrounding the medulla is the cortex. Unlike the flexible medulla, the cortex is stiff and rigid because it is composed of hard keratin and is the thickest of the three layers. A single layer of cells arising from the edge of the papilla form the hair surface, the cuticle, which is also composed of hard keratin. The cells of the cuticle are layered like shingles on a roof, which prevents the hairs from sticking together and forming mats. |
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Term
| What factors stimulate contraction of the arrector pili muscle? Why is this muscle important? |
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Definition
| The sympathetic nervous system stimulates the contraction of the arrector pili muscles when an animal is frightened or cold. This reaction is a defense mechanism designed to make the animal appear bigger and therefore less vulnerable to potential predators. In addition, hair that stands erect can better trap insulating layers of air than nonerect hair, so animals with erect hair coats stay warmer than animals with flat coats. The arrector pili muscle also is responsible for forcing sebum from the sebaceous gland, which helps keep the integument moist and supple. |
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| Where are anal sacs found and what is their importance to animals? |
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Definition
| Anal glands are located at the 5 and 7 o'clock positions relative to the anus. They are connected to the lateral margin of the anus by a small, single duct. When the animal defecates or becomes frightened, some or all of the anal sac contents are expressed, feces become coated with the secretions stored in the anal sac, and the unique smell of the animal is transferred to the environment. By excreting their own smell they mark their territory and attract a mate. |
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Term
| Name two types of sweat glands. How are they different from one another? |
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Definition
| There is the eccrine sweat gland and the apocrine sweat gland. They differ from one another in that the eccrine glands empty directly on the surface of the skin, whereas the apocrine sweat glands empty into hair follicles. In dogs, eccrine sweat glands are found only in the deep layers of the fat and connective tissue of footpads.In the dog, apocrine glands are located in the external ear canal. |
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Term
Which of these would you use skin scraping? (may choose more than one answer)
-Arthropod ectoparasites
-Exam of hair structute
-Cytology of pus
-Nematodes
-Bacterial culture
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Definition
| Arthropod ectoparasites and nematodes |
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Term
| What tests could you use to exam for dermatophyte infection? |
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Definition
| Wood's lamp, hair pluck, and skin scrape |
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| What test could you use to exam for Demodex infection? |
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Definition
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Term
Which of these tests are suitable for cytology?
-Hair plucks
-Tape strips
-Impressions smears
-Coat brushing
-Biopsies |
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Definition
| Tape strips and impression smears |
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Term
| What are they typical magnifications for a microscope eyepiece? |
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Definition
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| What total magnification (eyepiece x objective) would be suitable to exam a skin scraping for ectoparasites? |
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Definition
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| What total magnification (s) would be suitable to exam a tape strip for bacteria? |
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Definition
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| What objective would you normally use with immersion oil? |
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Definition
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| What objective(s) would the condenser to be lowered to get good contrast? |
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Definition
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| What is the purpose of a skin scrape? What indications or contraindications for their use? |
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Definition
| To identify mites on the skin. It is indicated for any dog or cat with alopecia, scaling , or pruritus. No contraindications. Good test for diagnosing Demodex mites which bury deep within the hair follicles, so squeezing the skin is needed. |
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Term
| What is the cellophane tape method used for? Indications or contraindications? |
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Definition
| To collect parasites and debris from the hair and skin surface for microscopic evaluation. Indicated for any generalized pruritus, especially with debris in hair or on skin surface. Especialy useful in assessment for Cheyletiella mites, flea larvae, and lice. Can also assess cutaneous Malassezia. No contraindications. |
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Term
| What is the purpose of vacuuming in detection of dermatological parasites? |
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Definition
| To collect parasites and debris from the hair and skin surface for microscopic evaluation. Especially useful during assessment for Cheyletiella mites, sarcoptic mange mites, fleas, and lice. |
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| What are the indications for a skin biopsy? |
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Definition
-When skin neoplasia is suspected.
-Dermatologic conditions that have not improved with rational therapy for the presumed diagnosis
-Dermatologic conditions suspected to be immune mediated in origin
-Dermatologic conditions that can be definitively diagnosed only by histopath
-Once parasitic disease has been excluded, skin biopsies sometimes can help differentiate pruritus due to inhaled environmental allergens from skin disease caused by food allergies. |
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| What is the purpose of using the Wood's lamp technique? |
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Definition
| To evaluate patients with lesions suggestive of dermatophyte (ringworm) infectsion |
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| List the causes (major categories) of skin disease. |
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Definition
ectoparasites (demodicosis, scabies, fleas)
-atopy (inhalant allergy – pollen, molds, dust mites, other allergens)
-food allergy
-otitis (inflammation of ear, usually secondary to underlying disease such as atopy)
-fungal or yeast infections (dermatophytosis, Malassezia dermatitis)
-endocrinopathy (hypothyroidism and endocrine alopecia)
-acral lick granuloma (behavioral, infection, foreign body, neoplasia, trauma) |
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Term
| Why is contact time important for topical therapies? |
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Definition
| -Adequate contact time is also necessary. Shampoos should remain on the patient for 10-15 minutes before rinsing, and patients must be prevented from licking/rubbing off topical preparations |
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Term
| What serious side effects can be seen with long-term administration of corticosteroids? |
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Definition
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Term
| What side effects can be seen with administration of topical and systemic corticosteroids soon after starting the treatment? |
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Definition
| May cause iatrogenic hyperadrenocoritcism |
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Term
| What topical medications should NOT be used in cats? |
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Definition
Pyrethroids, such as Permethrin (Insecticidal)
Refined tar, Selenium sulfide (Antiseborrheic) |
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Term
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Definition
| For removal and prevention of scales, and in some cases to remove excess oils. |
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Definition
| For the relief of itching due to conditions such as atopy and other allergies |
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Definition
| For treatment of bacterial infections such as pyoderma, folliculitis, and impetigo |
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Definition
| For treatment of ringworm and yeast infections |
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Definition
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Definition
| Help distribute emollients |
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