Integument

Integument

1. Skin and Derivatives

   • Hair
   • Horn
   • Hoof
   • Claws
   • Nails
   • Feathers
   • Scales

2. Most Extensive organ in body

3. Covers and protects whole body

4. Waterproof, abrasion resistant, cutaneous sensation

5. Three Layers

   • Epidermis
     • Protection
     • Stratified Squamos
     • Constantly renewed
     • Five layers
       • Corneum
         • Completely flat
         • Completely filled with keratin
         • 3/4 of total surface
       • Lucideum
         • Completely lose nucleus
         • Flatten more
         • Fill with keratin
         • Only present in very thick skin
       • Granulosum
         • No cell division
         • Cells begin to flatten
         • Keratin enters
         • Not found in thin skin
       • Spinosum
         • Spiny layer
         • Slower cell division
           • Further away from blood supply
       • Basale
         • Bottom layer
         • Contains only cells
           • Rapidly dividing
             • Rich blood supply from dermis
         • Find melanocytes here
     • Keratin
     • Top layer sloughs every 3 weeks
     • Avascular
   • Dermis
     • Forms majority of skins thickness
     • Vascular
       • Supports epidermis
       • Provides most structural strength
     • Connective tissue
     • Two layers
       • Cannot see where one starts and the other ends
       • Papillary Layer
         • Loose connective tissue
         • Finger like ridges project into Epidermis
         • Blood vessels nourish Basale of Epidermis
       • Reticular Layer
         • 80% of Dermis
         • Denser connective tissue
   • Hypodermis
     • Thick layer beneath Epidermis and Dermis
     • Loose connective tissue
     • Loose structure makes the skin mobile

6. Hairy Skin

   • Covered in scale like folds
   • Hairs emerge directed away from opening
   • Dogs have 3 hair follicles per scale
   • Dotted with small lumps
     • Tactile elevations - whiskers
       • Special awareness

7. Responds to pressure, trauma, inflammation

   • Recumbent or overweight animals have thicker skin due to more pressure

8. Fish Skin

   • Superficial living layers
   • Produce mucous
     • Aid waterproofing
   • Epidermis of outside over bony scales which originate from Dermis

9. Bird Skin

   • Relatively thin
     • Feathers
   • Little keratinsation other than on feet
   • Have feathers to protect Epidermis

10. Paw Pads

    • Padded - quiet
    • Thick fat and connective tissue layers
    • Supports animals weight
    • Toughest and thickest skin on the body
      • Take weight
      • Protect from environment
        • Hot, cold, rough, smooth surfaces
      • Provide cushioning - creep on prey
    • Highly pigmented
    • Rough feeling but can be worn smooth
    • Multiple
      • Carpal pad
        • Protection of blood vessels
      • Metacarpal/metatarsal
        • Weight bearing
      • Digital
    • Also have sweat glands

11. Planum Nasale

    • Nose
      • Unusual form of skin
    • No glands
    • Lots of little 'plates'
    • Usually pigmented
    • 3 epidermal layers
      • thin

12. Hair

    • Essential for survival
      • Temperature regulation
      • Camouflage
      • Communication
    • Thickest of most exposed surfaces
    • Three layers
      • Innermost
        • Medulla = core
          • 2/3 layers cells containing soft keratin
      • Middle
        • Cortex = stiffer + more rigid
          • containing hard keratin
      • Very edge of papilla = outer layer
        • Cuticle
          • Hard keratin
            • Cells overlap = smooth surface
    • Growth cycles
      • Shed to allow new growth
      • Amount shed
        • Genetics
        • Hair length
          • Long v Short
        • Spring and Autumn shed
          • Outdoor animals
            • Indoor animals shed less
        • Hormones
          • Post whelp/endocrine dz
      • 1. Dead, keratinised epithelial cells
        • 2. Push up and away from papilla = hair
          • 3. More cells produced at base (papilla)
            • 4. Hair lengthens
              • Anagen hair: max. length determined genetically
              • 5. At max. length hair stops growing and follicle shortens
                • 6. Resting period
                  • Telogen phase - weeks/years
                • Between anagen and telogen - Catagen phase
                  • Membrane between papilla and hair = complete separation
                    • Hair strand - round stubby end = club hair
    • Colour
      • Pigment
        • Cortex and medulla of hair
      • Melanin from melanocytes
        • Quantity and type determines colour
      • Dogs - 2 melanin types
        • Yellow/red & brown/black
      • Can be solid/patchy/just at tip
      • Melanin production decreases with age
        • New hairs go grey then eventually white
    • Types
      • Three
        • Guard/primary
          • Straight/slightly arched
          • Thick
          • Long
          • Dominant hair per compound follicle
        • Secondary/wool
          • Softer and shoter
          • Often wavy
        • Tactile/sinus
          • Probes/feelers
          • Whiskers
          • Sensory nerve endings

13. Glands

    • Sebaceous
    • Sweat
    • Tail
    • Anal
    • Mammary

14. Claws and Dew Claws

    • Hard
    • Often pigmented
    • Outer covering of distal digits
    • Defence
    • Traction in running, walking, climbing, hunting
    • Wrapped around ungual processes
    • Dew claws
      • Digit remnents - regression in evolution
    • Medial surfaces
      • Non-weight bearing

Images and files in the map