V ana L2

Skin Functions

protection, sensory, secretion, production, storage, thermoregulation, communication

Protection

Protects the underlying structures of the body; acts as a physical barrier against physical trauma; barrier against microbes; waterproof barrier; protects against damage from UV rays

Sensory

The surface of the skin ability to detect environmental stimuli; well supplied with many types of sensory nerve endings to detect: temperature, pressure, touch, pain

Sebum

produced by sebaceous glands

Sweat

in cats and dogs, it occurs in the footpads and nose

Pheromones

produced by specialized skin glands

Production

ultraviolet light from the sun converts 7-dehydrocholesterol present in the sebum into Vitamin D.; This activated within the kidney and liver; Increases the uptake and metabolism of dietary calcium

Storage

fat is stored under the skin as adipose tissue or subcutaneous fats.

Thermoregulation

Skin prevents heat loss by diverting blood away from the surface by: Vasoconstrictions; Erecting hairs to trap a layer of insulating

air; Having an insulating layer of fat.

Communication

production of pheromones; other scents produced for communication (e.g., glands of the anal sac); provides a means of visual communication

Epidermis

superficial layer; composed of stratified squamous epithelium; has multiple layers of cells that are continually renewed; New cells are produced in the deepest layers and are pushed upwards to the surface as a result of mitosis below; It avascular and receives its supply of nutrients from blood vessels within the dermis

Stratum corneum

Most superficial of the epidermal layers. The cells have no nuclei and are dead.

Stratum lucidum

The cells lose their nuclei and become clearer.

Stratum granulosum

The cells are flattened and the process of infiltration of the cells by

the structural protein keratin begins in this layer.

Stratum Spinosum

Spinous or prickle cell layer. This layer is composed of polyhedral

keratinocytes and are joined together with desmosomes

Stratum Basale

Consists of a single layer of dividing cells. Pigmented cells or melanocytes may also be present in this area

Dermis

Deep layer of the skin, upon which the epidermis sits; Composed of dense connective tissue with irregularly arranged collagen and elastic fibers; It has a generous blood vessels, nerves and sensory nerve endings; The hair follicles, sebaceous glands and sweat glands also lie within this layer

Hypodermis

A.k.a. Subcutis or Subcuticular layer; Not actually part of the skin; It is a loose connective tissue and fat lying beneath the dermis; Also contains elastic fibers, which gives the skin its flexibility; Where the subcutaneous injections are given

Keratinized appendages

Scales, hair, horns, hooves, claws

Skin glands

Associated or not associated with hair follicles; Special glands (scent gland, mammary gland)

Sebaceous glands

Secretes an oily substance known as the sebum

Modified Sebaceous gland:

Tail gland; Circumanal glands; Anal glands; Cicumoral glands; Ceruminous glands; Meibomian or tarsal glands

Tail gland

Found on the dorsal surface of the base of the tail; Concerned with individual recognition and identification.

Circumanal glands

Located around the entire circumference of the anus; Contribute to the individual smell of the dog

Anal gland

Lie within the walls of the paired spherical anal sacs, located on either side and just below the anus; Produce a foul-smelling secretion, expressed during defecation, coating the feces, and serve as a territorial marker

Circumoral glands

Found on the lips of the cats and their secretions is used for territorial marking

Ceruminous glands

Found in the external ear canal and secrete cerumen (ear wax)

Meibomian or tarsal glands

Open on the eyelids and produce fatty component of the tear films that moistens the eye

Shaft/scapus

The visible part of the hair, above the skin’s surface

Root/radix

The part of the hair that lies within the follicle

Anagen (growth phase)

Nourishment of hair follicle via blood supply enables hair growth

Catagen (transition phase)

hair follicle detaches from nourishing blood supply

Telogen (resting phase)

Without nourishment, the hair dies and falls out

Straight hair/protective hair, primary hair or cover hair

Strongest hair and the chief hair in the follicle bundle; Longest hair with the shaft

either straight or bowed

Bristle hair

Bristle with a spinelike tip; Regarded as an over-hair or protective hair; Subsidiary hair to type 1

Wavy Bristle hair

Finer and shorter than type 2; Wavy with a well-developed bristle

Bristle Wavy hair

Long, soft hair and is shorter and finer than type 3; Poorly developed bristle and smaller medulla; Wavy in the lower two-thirds of the shaft; Largest hairs of the undercoat.

Large Wavy hair

Finer and shorter than type 2; Shaft is very wavy with a small bristle on the tip; Gives a furlike or wool-like feel

Fine wavy hair

Shorter and finer than type 5; Represents the finest and smallest hairs of the undercoat; Wavy with poorly developed bristle on the tip.; aka. Vellus hair, fuzz, down, or lanugo hair.

Keratinized Appendages

Hair/Pili,Torus/Skin pads, Scales, Claws/Unguiculae, Hoof/Ungula, Horns/Cornu