Module 2 : Intergumentary System

• 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
  • A barrier against invasion by microorganisms
  • Acts as a waterproof barrier
  • Protects against damage from ultraviolet radiation
• Sensory


  The surface of the skin is well supplied with many types of sensory nerve endings to detect: Temperature, Pressure, Touch, Pain
• Secretion


  • Sebum produced by sebaceous glands
  • Sweat in cats and dogs 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
  • 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 through vasoconstrictions, erecting hairs to trap a layer of insulating air, and having an insulating layer of fat
• Communication


  • Production of pheromones
  • Other scents produced for communication
  • Provides a means of visual communication
• Skin/Cutis Structure


  • Epidermis
  • Dermis
  • Hypodermis
• Skin Structure - Epidermis


  1. Composed of stratified squamous epithelium

  2. Has multiple layers of cells that are continually renewed

  3. New cells are produced in the deepest layers and pushed upwards to the surface

  4. Avascular and receives nutrients from blood vessels within the dermis
• Skin Structure - Epidermis

  1. Most superficial layer with dead cells

  2. Cells lose their nuclei and become clearer

  3. Cells are flattened and keratin infiltration begins

  4. Spinous or prickle cell layer composed of polyhedral keratinocytes joined with desmosomes

  5. Consists of a single layer of dividing cells with possible presence of pigmented cells or melanocytes
• Skin Structure - Dermis


  1. Deep layer of the skin with dense connective tissue

  2. Composed of irregularly arranged collagen and elastic fibers

  3. Contains blood vessels, nerves, sensory nerve endings, hair follicles, sebaceous glands, and sweat glands
• Skin Structure - Hypodermis


  1. Also known as Subcutis or Subcuticular layer

  2. Not actually part of the skin but a loose connective tissue and fat beneath the dermis

  3. Contains elastic fibers providing skin flexibility
• Structures within the dermis

  • Sebaceous glands
  • Sweat glands
• Hypodermis is also known as Subcutis or Subcuticular layer
• Hypodermis is not actually part of the skin
• Hypodermis is a loose connective tissue and fat lying beneath the dermis
• Hypodermis contains elastic fibers, which gives the skin its flexibility
• Subcutaneous injections are given in the hypodermis
• Structures derived from the Skin

  • Keratinized appendages (Scales, hair, horns, hooves, claws, etc.)
  • Skin glands (Associated or not associated with hair follicles, Special skin glands such as scent gland, mammary gland)
• Structures derived from the Skin

  • 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)
• Structures derived from the Skin (Sebaceous glands)

  • 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 are 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 the fatty component of the tear films that moistens the eye)
• Shaft/scapus is the visible part of the hair, above the skin’s surface
• Root/radix is the part of the hair that lies within the follicle
• Types of Canine Hair

  • Straight hair/protective hair, primary hair or cover hair
  • Bristle hair
  • Wavy bristle hair
  • Bristled wavy hair
  • Large wavy hair
  • Fine wavy hair
• Straight hair/protective hair, primary hair or cover hair is the strongest hair and the chief hair in the follicle bundle, longest hair with the shaft either straight or bowed
• Bristle hair is bristle with a spinelike tip, regarded as an over-hair or protective hair, subsidiary hair to type 1
• Wavy Bristle hair is finer and shorter than type 2, wavy with a well-developed bristle
• Bristle Wavy hair is 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 is 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 is shorter and finer than type 5, represents the finest and smallest hairs of the undercoat, wavy with poorly developed bristle on the tip, also known as Vellus hair, fuzz, down, or lanugo hair
• Keratinized Appendages


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