Module 2 - Skin

Module 2 - Skin

1. Epidermis

   • Superficial layer, mainly epithelial tissue, protective covering
   • Cells
     • Keratinocytes
       • Produce Keratin
       • Toughness and Waterproofing
     • Melanocytes
       • Synthesise Melanin
       • Protects DNA against UV radiation
     • Langerhans
       • Macrophages (WBCs)
       • Involved in immune response
     • Merkel
       • Free Nerve endings with disc
       • Detects TOUCH sensation
   • Skin Colour
     • Melanin
       • pale yellow - tan black
       • melanocytes don't vary , the type of pigment that is produced
     • Carotene
       • yellow - orange
       • in stratum corneum, fatty dermis and subcutaneous layers.
     • Haemoglobin
       • pink - red
       • dependent on amount of oxygen content of blood moving through capillaries
   • Stratums/Layers (Beautiful Skin Glows Like Copper)
     • Basale
       • base layer
     • Spinosium
       • 'spine-like'
     • Granulosum
       • Keratin granules and glycolipid granules
     • Lucidum
       • extra layer only in palms and soeles
     • Corneum
       • outer region: dead keratin and glycolipid cells (still protect)

2. Dermis

   • Papillary Region
     • Superficial
     • Areolar (loose) connective tissue
     • Capillary networks to feed epidermis
     • Meissner corpuscle and free nerve endings = touch and pain
   • Reticular Region
     • Deeper
     • Dense, irregular connective tissue
       • Collagen and Elastic Fibres provide strength, extensibility and elasticity
     • Adipose cells, hair follicles, nerves, sebaceous (oil) glands, and sudoriferous (sweat) glands
       • Exocrine Glands (Via Duct)
         • Sebaceous (oil) glands
           • through hair follicle
           • sebum (oil) keeps the hairs from drying out and becoming brittle
         • Sudoriferous (sweat) glands
           • through hair follicles and/or directly to skin
           • Eccrine: maintains temperature
           • Apocrine: oiler product, stimulated by hormones
       • Hair (Pili)
         • Protection
         • Thermoregulation
         • Hair follicles have two regions
           • Shaft
             • Projects from the surface of the skin
           • Root
             • Deep to the shaft, penetrates the dermis

3. Hypodermis

   • Superficial fascia/ Subcutaneous
   • Adipose Tissue
     • Shock absorber and insulation
   • Areolar Tissue
     • Anchors the skin to muscle

4. Functions

   • Protection
     • Chemical
       • acidic inhibits bacteria
       • secretions and melanin protect against UV rays
       • Defensins poke holes and 'retards' bacterial cells
     • Physical/Mechanical
       • Continuity of skin and hard keratinised cells
       • waterproofing from glycolipids
       • limited penetration of skin by lipid-soluble substances
     • Biological
       • Dendrite cells (Langerhans), Macrophages and DNA
   • Cutaneous Sensations
     • Touch, Temperature and Pain
       • Sensory receptors
       • Sense pain
       • Adapt to stimuli
       • Alert us to movement
   • Metabolic Functions
     • Synthesis of Vitamin D precursor (inactive form)
       • Vitamin D increases absorption of calcium from the digestive tract
   • Blood Reservoir
     • Up to 5% of body's blood volume to be directed where needed (to core)
   • Excretion
     • Waste from proteins (nitrogenous) and salt in sweat
   • Temperature Regulation
     • Elevated heat:
       • Insensible Perspiration
       • Sensible Perspiration
     • Decreased heat:
       • Arrector Pili Muscle
       • Vasoconstriction of blood vessels

5. 4 Stages of Wound Healing

   • Haemostasis
   • Inflammatory Phase
   • Proliferation (organisation) Phase
   • Maturation (regeneration and fibrosis) Phase

6. Degrees of Burns

   • First Degree
     • Epidermal damage only
     • Localised redness, edema and pain
   • Second Degree
     • Epidermal and Upper dermal damage
     • Blisters appear
   • Third Degree
     • Entire thickness of skin damage
     • grey - white, cherry - red or black
     • No initial pain or edema (nerve endings are destroyed)
     • Skin grafting usually required to repair