Anatomy of the Skin and a Clinical Approach to Patients with Skin Disease

Transcription

1 C H A P T E R Anatomy of the Skin and a Clinical Approach to Patients with Skin Disease 1 1 This manual will begin with a brief revision of the main structures and functions of the skin. Much of this manual describes what the different skin diseases look like and gives some common terms which will help describe skin diseases. Essentially, a clinical approach to skin disease will concentrate on what the skin lesions look like. This chapter will cover the following. Dermatology is the study of skin. derm = skin and ology = study c Anatomy of the skin c Important functions of the skin c Common skin lesions c Taking a history of a patient with a skin disease. c Examining a patient with a skin disease. The anatomy of the skin The skin has three main layers. c The epidermis is the outer covering of the body. On the outside of this layer is the keratin layer. You see keratin when your skin peels. The pigment containing cells called melanocytes are found in this layer. Skin layers Epidermis Dermis Subcutaneous layer Hair Nerve endings Sweat pore Sweat duct Sebaceous gland Hair follicle Sweat gland Fat cells in subcutaneous layer Cross-section of the surface of the skin.

2 c The dermis is a thicker middle layer. It contains hair follicles, sweat glands and sebaceous glands. Nerves and blood vessels are found in this layer. It contains tough protein fibres called collagen and also stretch fibres called elastic fibres. c The subcutaneous layer is mainly a layer of fat. c The sweat glands produce sweat. The sweat travels through a sweat duct to the surface of the skin. c A hair follicle holds each hair. A sebaceous gland is attached to the hair follicle. The sebaceous gland excretes an oily substance which keeps the hair and skin surface slightly oily. The important functions of the skin The major function of the skin is to protect the internal structures of the body from the outside environment. The skin protects the body in the following ways: c The keratin of the epidermis gives the body a waterproof cover so that water is not absorbed into the body nor lost from the body through this layer. c The pigment in the epidermis protects the skin from the harmful ultraviolet rays of the sun. Thus dark skinned people are well adapted to living in sunny countries and rarely develop skin cancer. Light skinned people especially red haired people do not have this protection and skin cancer is common amongst them. c The skin with its different layers protects the inner body from trauma. The dermis provides strength and elasticity to the skin. The fat layer has a cushioning effect. c The skin regulates the body temperature: Blood vessels bring blood to the surface of the skin where heat is lost. Thus if we have a high temperature or if we are exercising on a hot day our faces flush. Sweating results in evaporation of water from the surface of the skin and cooling of the body. The fat layer insulates the body so that it does not become too hot or too cold even though the temperature outside may be freezing cold or very hot. c Because of the rich supply of nerves to the skin it is a sensory organ of touch, pain, pressure, heat and cold. Skin disease is easy to see Skin diseases can be said to be "written" on the skin, not in words but in pictures. The pictures are made up of different kinds of lesions which tell us about the skin disease. It is important to recognise and "read" the different lesions which are signs of the different skin diseases.

3 Common skin lesions that present in skin diseases There are many different kinds of skin lesions that should be recognised. A variety of clinical terms are used to describe different skin lesions. Try to learn what each term means and what each lesion looks like. On the following page, clinical terms are listed and there is a diagram of the common skin lesions that can occur. Taking a history of a patient with a skin complaint Skin disease can usually be diagnosed by simply looking at the skin lesions. But the history is also very helpful. Here are some important questions to ask patients about their skin lesions. Important questions: c How long has the patient had the lesions? This will help us know if the problem is acute or chronic. c What part of the body are the lesions on? Different skin diseases affect different areas e.g. ringworm affects the scalp. Pimples affect the face, chest and upper back. Scabies is often found between the fingers. The distribution of lesions is very important. Are they: on the head and neck on the trunk of the body on the genitalia and perineum in the creases e.g. the elbow associated with the hairs or nails on the hands and palms on the feet and soles c Are there any other symptoms? eg. fever, itchiness, pain, loss of sensation. c Has the patient had this skin problem before? c Do other family members have the same problem? This will help us decide if the disease is genetic or contagious. c Is the patient taking any medications? The patient may be taking medicine for the skin problem or any other problem. Many medicines can cause skin rashes. c What are the patient's habits? What work does he do? The patient may be allergic to substances at work e.g. cement, machine oils or glues. He may be allergic to substances at home e.g. detergents, cosmetics or metal in jewellery. c What is the general health of the patient? Some diseases e.g. diabetes cause skin problems. AIDS is a common cause of skin problems and often presents for the first time with rashes and skin lesions. After taking the patient's history, the patient needs to be examined carefully.

4 Pustules Pustules are small vesicles which contain pus. Streptococci or Staphylococci bacteria are usually the cause of pustules. Vesicles Erythema A vesicle is a lesion which is raised and has fluid in it. It may have a shiny look. A vesicle is a small blister. It will be smaller than 0.5 cm. Redness of the skin. Erythema is usually caused by dilatation of the blood vessels in the surface of the skin. Papules A papule is a small raised lesion on the skin. It may or may not be discoloured. A papule can be felt e.g. a mole. Macules Macules are flat marks on the skin. They are discoloured. You can see them clearly but you cannot feel them with your finger because they are flat e.g. flat birthmarks. Bullae Bullae are large blisters of more than 0.5 cm which contain fluid. Ulcers An ulcer is a sore in the surface of the skin. It lies in the epidermis and upper dermis. It breaks the surface of the skin and heals with scarring e.g. a bedsore. Dermatitis is inflammation of the skin. Remember derm = skin. Eczema is a different word for dermatitis.

5 Examination of a patient with a skin complaint Always examine the patient in good bright light. It is very important to see the different lesions clearly. Examine the whole body, including the hands, feet, hair and genitals. Examine the lesions carefully. Note the following: the type of lesions e.g. macules, papules, vesicles, pustules or ulcers where are the lesions? This will tell us about the skin problem and often even provide the diagnosis Examples are: scabies causes itchy papules between the fingers and in the groin. Atopic eczema causes lesions in creases of the elbows and knees. Ringworm is often found on the scalp but only in children Other fungal infections occur between the toes (athletes foot) Herpes simplex may occur on the lips or the genitals. Herpes zoster occurs on one side of the body only and stops at the midline. Pellagra occurs in sites exposed to the sun e.g. the neck, face and forearms. facial cosmetics can cause skin allergies on the face dish soap can irritate skin on the fingers Seborrhoeic dermatitis is found in the hairy areas such as the scalp axillae and groin. Are the lesions wet, dry or scaly? Is there pus or liquid in the lesions? If there is a swelling, is it fluctuant? Are there signs of inflammation? e.g. redness, tenderness, swelling, raised temperature in the lesions. Are there any scratch marks? Is there sensation in the skin? Loss of sensation is a sign of leprosy. Do a quick brief general examination. Check if there is any generalised illness e.g. pyrexia, general enlarged lymph nodes, enlarged liver or spleen. Do a urine test for glucose in patients with recurring bacterial infections of the skin. Remember that diabetics get skin infections very easily and that AIDS may present with infections in the skin. When you diagnose skin disease, take special note of what the lesions look like and which part of the body is affected