SKIN CARE PART 1 AND 2

• When analysing markets, a range of assumptions are made about the rationality of economic agents involved in the transactions
• The Wealth of Nations was written

  1776
• Rational


  (in classical economic theory) economic agents are able to consider the outcome of their choices and recognise the net benefits of each one
• Rational agents will select the choice which presents the highest benefits
• Producers act rationally by


  Selling goods/services in a way that maximises their profits
• Workers act rationally by


  Balancing welfare at work with consideration of both pay and benefits
• Governments act rationally by


  Placing the interests of the people they serve first in order to maximise their welfare
• Rationality in classical economic theory is a flawed assumption as people usually don't act rationally
• A firm increases advertising

  Demand curve shifts right
• Demand curve shifting right

  Increases the equilibrium price and quantity
• Marginal utility


  The additional utility (satisfaction) gained from the consumption of an additional product
• If you add up marginal utility for each unit you get total utility
• Skin is the outer covering of the body and is the largest organ of the integumentary system
• An inch of your skin has approximately 18 million cells and 6000 melanocytes and also 1000 nerve endings and 20 blood vessels
• In average adult, skin covers a surface area in excess of 2m2. With the exception of the skeletal muscles, the skin is the heaviest organ in the body
• In adults, in our age. The skin covers 15% of our total body weight. (E.g 75kg person, 11kg was from the skin)
• Types of skin


  • Glabrous
  • Hairy
• Glabrous skin


  Non hairy skin found on the palms and soles of the feet, lacks hair follicles and sebaceous glands but has a very thick epidermis and encapsulated sense organs in the dermis
• Hairy skin


  Hair follicles and sebaceous glands are both present, but there are no encapsulated sensory organs. Facial skin has large sebaceous glands associated with fine vellus hairs, contrasting sharply with the scalp, which contains large hair follicles
• Thick skin has a thick epidermis (0.64.5 millimeter) containing 5 layers, lacks hair follicles and contains sweat glands
• Thin skin has a thin epidermis (0.1 – 0.15 millimeter) containing 4 layers, has hair follicles and sebaceous glands
• Skin


  • Serves as first line of defense against bacteria, viruses
  • Protects underlying structures from UV radiation dehydration
• Functions of the skin

  • Vitamin D production
  • Sensation
  • Excretion
  • Body temperature regulation
• Vitamin D production


  Skin starts as a precursor to dehydro-cholesterol before it became vitamin D, needed to be absorbed to UVB – after absorbed it will convert to vitamin D3. Vitamin D3 will be metabolized to Kidney by hydroxy vitamin produce dihydroxy vitamin -> converted to Vitamin D (calcitriol – active form of Vit D ones needed to calcium absorption)
• Vitamin D is the only vitamin that our body can produce naturally
• Sensation


  Sensory receptors, feeling of itchiness and pain etc
• Excretion


  Small amounts of waste products are lost through perspiration
• Body temperature regulation


  If too hot, blood vessels dilate. Vessels carry more blood surface so heat can escape. If too cold, dermal blood vessels constrict, this prevent heat from escaping
• A vertical section of the skin reveals three distinct layers, namely the outermost epidermis, the dermis and finally the hypodermis or subcutaneous layer
• Epidermis


  Avascular structure, made up of many layers of cells, classified as stratified squamous epithelium, responsible for producing the main barrier known as the horny layer or stratum corneum
• Horny layer


  Made up of water resistant dead cells, called corneocytes, which are segmented together with a complex lipid material
• Layers of epidermis


  • Germinative or basal layer
  • Stratum spinosum or prickle cell layer
  • Stratum granulosum or granular layer
• Keratinization


  The dynamic process of epidermal renewal, begins in the basal layer where the cells, known as keratinocytes, multiply by mitotic cell division and are continually pushed upwards whilst producing the protein, keratin
• Desquamation


  The process where the dead, water resistant flakes in the horny layer are lost to the environment
• Dermis


  Functions as a supporting frame to the epidermis, supplying it with nutrients via the blood capillaries. It also supports the sensory nervous system, secretory glands and hair follicles
• Composition of dermis


  • Collagen and elastin
  • Ground substance
  • Mast cells
  • Sweat glands
  • Sensory skin receptors
• Collagen


  Forms the major constituent of the fibrous protein which gives the skin its tensile strength
• Elastin


  The second type of protein fiber, interwoven among the collagen bundles, allows the skin to deform and return to its original state once the pressure or tension is removed
• Ground substance


  Consists of salt, water and glycosaminoglycans, the latter form complexes with protein molecules known as proteoglycans. Hyaluronic acid is known to play a vital role in the hydration of tissues since it carries with it a large volume of water
• Mast cells


  Responsible for synthesis and secretion of heparin, histamine and prostaglandins