Module 7

• How would you 'classify' the type of epithelium

  that forms the epidermis of thin hairy skin?


  Stratified keratinised squamous epithelium
• What type of connective tissue forms the dermal layer of the skin?

  Dense irregular connective tissue
• What type of hair follicle is represented in this image?

  Simple hair follicle

  
• A = Stratum Basale -stem cells or undifferentiated keratinocytes. B = Stratum Spinosum. C = Stratum Granulosum. D = Stratum Corneum. E = Stratum Basale - Melanocytes.


  Label this image

  
• 1 = Epidermis. 2= Hair bulb- dermal papilla. 3= Sweat glands. 4 = sebaceous glands


  Label this image

  
• Name another domestic animal of veterinary significance that would have the same type of hair follicle as that found in equine skin.


  Bovine
• What name is given to the muscle which causes a hair to become erect?

  Arrector pili muscle
• What type of muscle fibre causes the hair to become erect?

  Smooth muscle
• A= hair follicle- bulb. B= Root of the hair follicle


  Label this image

  
• Name the different layers that comprise the hair.

  Medulla, cortex, and cuticle (inner to outer layer)
• Where would you find the keratogenous zone of this hair follicle and what happens in this zone?


  Just above the bulb, this is where the hair matrix cells that give rise to the hair and parts of the hair follicle will become keratinised.
• What is the embryological origin of these melanocytes?

  The neural crest area during embryonic development and actively migrate to the dermal-epidermal border of the skin and the hair bulb region of the hair follicles.
• Sweat Gland


  What type of skin gland is in this image?

  
• In what context have we previously discussed the functional role of myoepithelial cells?


  Mammary glands
• Where do the excretory ducts associated with a) sweat glands and b) sebaceous glands terminate in thin hairy skin?


  Into the hair follicle- sebum and sweat coat the emerging hair shaft
• What is the function of the secretory product produced by sebaceous glands?


  Waterproofs and gives hair its lustre
• Sebaceous gland


  What type of skin associated gland is indicated by the arrow?

  
• What is the functional role of sebaceous glands?


  To produce sebum
• By which secretory process do the secretory cells release their product in this type of glandular?


  Holocrine
• How does the secretory product produced by this glandular tissue reach its target area?


  Via a duct - this is an example of an exocrine gland
• What type of tissue primarily gives rise to the hypodermis?


  Adipose tissue
• A = Primary hair follicle. B = Secondary hair follicle. C = Sweat gland. D = Secondary hair follicle. E = Sebaceous glands.


  Label this image

  
• Are dermal papillae a feature of thin hairy skin?


  No
• Why aren't dermal papillae a feature of thin hairy skin?


  In thin hairy skin, the hair follicles which originated in the deep dermis serve to anchor the two layers together.
• Keratohylin granules react with H&E stains and are visible with the LM (note lamellar granules are also found in the cells of the stratum granulosum- but these are not visible with the LM).


  What type of granules are visible in stratum granulosum in this image (stain H&E)?

  
• Is the stratum lucidum layer present in thin hairy skin?


  No, this is only a feature of thick hairless skin.
• Why is the stratum corneum thinner in thin hairy skin?


  The epidermal surface is protected from surface abrasion by the presence of hairs which project above the skin surface.
• What name is given to the terminal part of  sweat gland duct system in  thick hairless skin


  Sweat pore- these are visible on the epidermal surface
• Are sebaceous glands a feature of thick hairless skin? 


  No
• Compound hairs and the thin epidermis associated with thin hairy skin on visible on the left; Thickened epidermis and no hairs are shown on the right.


  List two features that you can see in this image that would allow you to distinguish between the two skin types.

  
• Masons trichrome stain


  Which histological staining method has been used to stain this section?

  
• Apart from size list one major distinguishing feature of the sinus or tactile hair.


  Blood-filled sinus present as part of the hair follicle
• Outcomes of acute inflammation?


  Abscess formation, resolution, healing by repair, chronic inflammation
• Factors that determine the outcome of acute inflammation?


  The severity of tissue damage, the ability of cells to regenerate, and cause of injury.
• If an injury has persistent tissue damage, what is the outcome?

  Fibrosis/scar formation
• If the tissue injury is acute(stimulus removed) and the tissue frame work is intact, what is the outcome?


  Repair: regeneration, restitution of normal structure (=restoration)

  Examples include liver regeneration after partial hepatectomy.
• If the tissue injury is acute (stimulus removed) and the tissue frame work is damaged, what is the outcome?


  Scar formation

  Examples include deep incisional wounds,myocardial infracts
• Definition of Repair


  Two possible outcomes, regeneration or scarring.
• What is regeneration?


  Replacement of damaged tissue components and return to a normal state
• Mammals have limited capacity for regeneration