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The Skin

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Chapter 1: The Skin Structure and Function
Chapter 2: Changes In the Skin Due to Ageing
Chapter 3: Sun and lha Skin
Chapter 4: Reversing Sun Damage
Chapter 5: Skin Cancar
Chapter 6: Problems with Dark/Pigmented Skin
Chapter 7: Dry Skin And How To Deal with it
Chapter 8: Acne
Chapter 9: Eczema and Psoriasis
Chapter 10: Facts About Treating Skin with Cortisone
Chapter 11: Fungal Infections
Chapter 12: Bacterial and Viral Infection
Chapter 13: Hair and Nails
Chapter 14: Cosmetic Dermatology

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Ebook, Printed

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INTRODUCTION The skin is the body's largest organ and the most obvious. With its appendages, the hair and nails, it is that aspect of the individual presented to the world.As a result many people spend a great deal of time and vast sums of money in an attempt to preserve its appearance with age. There are many half-truths and absolute myths the women's magazines and journals. Many of these are propagated by the women's magazines and journals. However there is much that can safely be done to look after and preserve it based on scientific research and evaluation.

One purpose of "The Skin" is to explain what changes to expect in the skin form youth to old age. In parallel with this it is intended to illustrate what can be done to prevent excessive abuse from agents such as the sun, and changes due to physical damage. In addition, attention is given to some of the more common skin conditions in order to emphasise the measures no available for their treatment. Understanding of both the natural changes in the skin and its disease processes have advanced enormously in the last few years although much still remains to be discovered. There is a greater appreciation of the available help from both preventative and cosmetic aspects. For the common disease states there are many new innovations. Most people want to have a good skin, many wish to be admired while others require relief for cosmetic reasons or for discomfort. It is intended through this book to give a better understanding and to summarise what is currently available. It is hoped that this will direct the reader to better care or treatment of his or her skin. It is a fact, for instance, that most people get 80% of their whole life's sun exposure before the age of 20. It must also be hoped that any lessons learnt by the adults who read this book will be applied to their children whilst the opportunity still exists. 2015-12-15 01-42-38 PM

Dr David Presbury MB BS FRCP Consultant Dermatologist Johannesburg

2015-12-15 01-43-26 PM

Dr Noori Moti-Josuub MBBCh (WITS), FC DERM(SA) Consultant Dermatologist Johannesburg

CHAPTER 1

 

The Skin Structure and Function The skin is a multilayered structure covering the whole body and Is actually the body's largest organ.It consists of three layers -the epidermis (the outer layer),the dermis (the thick part which one feels when the skin is picked up) and the subcutaneous tissue which is really the fatty cushion on which the skin rests

 

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The structure of the skin

The epidermis rests on the dermis and has no blood supply of its own. The cells at the deepest level divide and migrate outwards changing as they progress, ultimately degenerating to form the keratin on the outer part of the skin. This is the horny layer which forms a vital barrier. There is a continuous process of replacement of the epidermis each month. Melanocytes, the pigment cells, are found in the deepest part of the epidermis. They produce the melanin, which is responsible for the natural colour of our skins, and which darkens in response melanocytes per square centimetre of skin. It is the amount and type of melanin produced that determines the natural colour of the skin.

The dermis is a great deal thicker than the epidermis and consists mainly of collagen and elastic fibres which give it strength and suppleness. Apart from offering very adequate protection for the underlying tissue it also forms a support for the blood vessels supplying the skin and the appendages. Changes in blood flow are also important in temperature regulation. There are many nerves in the skin transmitting various sensations and activating the appendages. The dermis also contains the smooth muscles of the arrectores pili, the muscles to the hair follicles. The skin appendages HAIRcovers the whole body except for the palms and soles. Lanugo hair is present at birth but falls out soon afterwards. Vellus hair is fine and pale and is found all over even in the areas that do not appear to be hairy, except for the palms and soles. Terminal hair is the thick. darker hair that is found on the scalp and in other areas after puberty. Hair is formed in the bulb at the base of the hair follicle and grows outwards from that point. There are three phases of hair growth - a long growing phase, a short transitional phase followed by a resting phase. It is in the last phase that the hair is shed before a new one grows. NAILS These basically improve our grip and protect the end of the dig tis. like hair they are made of specialised keratin. The nail is formed at the matrix and grows outwards. Nail growth is affected by physical damage and various skin diseases. Conditions affecting the hair and nails will be dealt with in a later chapter. SEBACEOUS GLANDS These are found all over the body except for the palms and soles. They make sebum, a greasy material that is excreted onto the surface via the hair follicle. They only become active at puberty under the influence of hormones. SWEAT GLANDS These occur all over the body and are active from birth. They open via ducts directly onto the surface. Emotional sweating occurs in the armpits and from the palms and soles. Sweating associated with temperature regulation occurs particularly on the face and trunk. Functions of the skin 1. barrier 2. mechanical 3. sensory 4. synthesis of vitamin D 5. temperature regulation 6. sociosexual communication

The skin as a barrier The skin acts as a two-way barrier preventing the outward passage of water and our natural chemicals and the inward passage of water and other chemicals which might easily be harmful if they were able to penetrate. The main barrier is the surface of the skin itself. Mechanical functions It is clearly important that the skin should be mechanically tough in order to resist all sorts of trauma to which It is subjected daily. The elasticity of the skin depends on the collagen and elastic fibres in the dermis which degenerate naturally with age. Sensory functions The sensations of touch, pressure, warmth, cold and pain are all perceived in the skin. The nerve endings transmitting these various sensations are not distributed evenly over the whole skin surface. It is necessary,for instance, for the fingers to be especially sensitive. Synthesis of vitamin D Vitamin 03 is essential for skeletal development. It controls the amounts of calcium and phosphorus absorbed from the small intestine and moved in and out of our bones. Vitamin 03 is synthesised in the skin as a result of exposure to ultraviolet B (UVB) radiation. After the Industrial Revolution in Europe, the pollution preventing the penetration of natural sunlight allowed vitamin D3 deficiency to become common leading to the abnormaldevelopment of bones in children, a condition known as rickets. There is now much debate over the fact that the obsessive use of sunscreens may prevent the synthesis of adequate amount of vitamin D allowing the occurrence of rickets to increase again. Also vitamin D deficiency has been implicated in the cause of certain cancers and other diseases, such as multiple sclerosis, so a great deal of research is currently being carried out. Temperature regulation It is important for our body's health to maintain a constant temperature. It is obvious that sometimes we may need to let off excessive heat and at others retain it There are two main methods of activating this. Firstly the blood vessels are arranged in layers in the dermis so that the more superficial ones may be dilated or constricted according to the current needs. This may lead to the skin looking either more red or blue than normal. Secondly we produce sweat and lose heat through its evaporation either on an ongoing basis during hot weather or in the shorter term during and after exercise. Sociosexual communication The skin by its appearance, feel and smell plays an important role in social and sexual communication in humans as it does in other animals. Visual communication is important to man.Apart from gestures, facial expressions and eye contact, a good skin is definitely a favourable characteristic and this forms the basis for the massive cosmetic industry. Touch is a vital part of sexual behaviour and a smooth skin in the female is undoubtedly regarded as a bonus.Thus skin disease in the form of a rash or pimples is often perceived by the sufferer as unattractive and socially unacceptable. A person with a rash on the hand is often reluctant to even shake hands. Smell certainly influences human behaviour. There is much debate as to whether we actually produce the special scents known as pheromones that are commonly used by other mammals to signal to members of the same species. We certainly do produce chemicals known to be used for the purpose in other animals but the human race SP.ends a great deal of energy washing and powdering the areas associated w1th odour- perhaps to hide the truth of our feelings about them. It is not certain why woman use perfume. It may be to attract men but it may equally be to please themselves. Certainly "correct smeW cannot be discounted as important to the human race.