What Are the Skin and Hair Coat?
The skin and hair coat comprise the outer covering of the body and the skin is the largest organ of the body. Together with the claws, pads and skin glands, they form the integumentary system. Where Are the Skin and Hair Coat Located?
The skin is located on the outer part of the body and covers the muscles, skeleton and internal organs. The hair coat is located on the external part of the skin. What Is the General Structure of the Skin and Hair Coat?
The skin consists of an outer cellular, avascular layer called the epidermis, and an inner fibrous corium or dermis that rests on a supporting layer of fat and very thin muscle.
The epidermis is the body's environmental shield. It is made up of tough keratinized cells that are continuously formed and shed from the surface. In some animals and in some areas of the body, epidermis contains dark brown pigment that screens the body from harmful rays of the sun and gives the cat his distinctive color. The dermis is composed of a network of connective tissue that also contains nerves, blood vessels, hair follicles, and sweat and oil glands.
The basic unit of hair production is the hair follicle (folliculus pili
). Each follicle has one guard hair and up to 15 secondary hairs emerging from the same follicle. These under-hairs grow as a tiny tuft of hair and can be seen to sprout from the pore of the follicle.
Each hair is made up of the root, seated within the skin itself, and the shaft, which is the visible portion of the hair. Most cats have three types of hairs. Guard hairs are the coarse, long, straight hairs found in the outer coat; awn hairs are of medium length and make up the intermediate coat; and soft, short downy fur that's curly or crimped composes the undercoat. Sinus hairs or vibrissae, also called whiskers, project from the body and act like antennae by allowing cats to feel air currents and movements.What Are the Functions of the Skin and Hair Coat ?
The skin and hair coat combined are the cat's largest sensory organ, monitoring the environment and influencing body temperature.
The skin has many important functions. It prevents desiccation and dehydration, acts as a sensory organ, and is the receptor for the perception of touch, pressure, vibration, heat, cold and pain. It prevents trauma, protects against invasion of microorganisms and noxious chemicals, and regulates temperature changes within the body. It also acts as the site of vitamin D synthesis. The subcutaneous tissues serve as a reservoir for fat, electrolytes, water, carbohydrates and proteins. Secretions from skin glands waterproof and lubricate the skin and function as pheromones (substance secreted by one individual that allows a second individual to recognize it). Skin may reflect the state of health of the animal, as well as indicate the presence of internal diseases.
The hair coat serves as an insulating layer between the cat's skin and the external environment. It protects him from the cold in winter, and the heat and sun in the summer. It also serves as aggressive display, as when the "hackles rise" on the back when the cat is threatened or frightened. All cats have fur, although the amount and type of hair coat varies from cat to cat, and from breed to breed. Even the "hairless" cats like the Sphinx breed typically have a peach-fuzz coat of velvety fur. What Are the Common Diseases of the Skin and Hair Coat?
Many skin diseases are lifelong problems requiring continual or frequent treatments by owners and veterinarians. Common diseases that affect the skin are: Dermatitis or inflammation of the skin is caused by numerous agents like irritants, allergens, and bacterial, viral, parasitic and fungal infections. These diseases include contact dermatitis, flea allergy dermatitis, atopy, ringworm or dermatophytosis, and pyoderma.
Parasitic diseases are also common. They include notoedric mange, sarcoptic mange, ear mites, the migration of parasite larvae, and flea, tick, and lice infestation.
Numerous degenerative diseases of the skin and hair coat may occur. These include various forms of alopecia, such as feline symmetric and excessive shedding.
Immune-mediated skin diseases may also develop, such as the pemphigus complex, food hypersensitivity, atopy (inhalant allergy), pododermatitis, and vasculitis.
Skin and hair coat changes are a common manifestation of hormonal (endocrine diseases), such as hyperthyroidism, hyperadrenocorticism (Cushing's disease), and sex hormone abnormalities.
Nutritional deficiencies, such as protein deficiency, fatty acid deficiency, and vitamin B deficiency may cause skin and hair coat changes.
Numerous forms of skin cancer also occur in the cat. While some skin tumors are benign, there is a high incidence of malignant tumors in the cat.
Some very rare skin diseases in the cat arise from abnormal immune reactions, and form areas of persistent, sterile inflammation. Examples include sterile pyogranulomas, sebaceous adenitis, injection reactions, feline eosinophilic complex, etc.
What Types of Diagnostic Tests Are Used to Evaluate the Skin and Hair Coat?
Complete blood count, biochemistry profile, urinalysis, and fecal tests to evaluate general health
Serum immune tests
Microscopic examination of skin scrapings
Microscopic examination of hair shafts
Fungal and bacterial cultures
Intradermal and serum allergy testing