Functions and Structure of the Skin PDF

Functions and structure of the skin  There are 7 main functions of the skin namely:  Sensation  Heat regulation  Absorption  Protection  Excretion  Secretion  Vitamin D production Sensation Acts as a sense organ to detect changes in the environment such as h...

Functions and structure of the skin  There are 7 main functions of the skin namely:  Sensation  Heat regulation  Absorption  Protection  Excretion  Secretion  Vitamin D production Sensation Acts as a sense organ to detect changes in the environment such as heat, cold, touch, pressure and pain. Heat regulation Helps to keep body at a constant temperature of 37C by dilation (widening) and constriction (narrowing) of the blood vessels. Sweat evaporation also keeps the body cool. The subcutaneous fat insulates the body. Absorption The skin has a limited amount of absorption properties. It can absorb certain particles that are small enough to be absorbed such as female hormones, nicotine patches, ingredients within facial preparations etc. Protection A waterproof coat protects the body against dirt, bacterial infection and chemical attack. 1. Acid mantle pH 5.5 ( made up from sebum and sweat) discourages growth of bacteria and also fungi. 2. The horny layer of the epidermis acts as a filter against bacteria. 3. Melanin in the epidermis protects against damage form ultra violet rays. Excretion Waste products such as lactic acid, urea and salts are lost through perspiration, however this is only a minor function. Secretion Sebum is secreted by the sebaceous glands. Vitamin D production This occurs due to the reaction of sunlight on the skin producing a chemical reaction.  Layers of the Skin The skin is made up of 3 main layers:  Epidermis  Dermis  Subcutaneous layer/ Hypodermis  Epidermis - This is the outermost layer of the skin (the part that you can see), it does not have a blood supply of its own and is made up of 5 layers  Dermis - This layer is often referred to as the true skin as it forms the bulk of the skin. The dermis contains 2 layers.  Appendages - Within the dermis are various other structures known as appendages.  Subcutaneous layer/Hypodermis - This is located under the dermis and is mainly made up of fat cells (adipose tissue).   Horny layer – the outer layer of the skin, this is made up of scale like cells which are continuously shed (corn flakes).  Clear layer - this is made up of small transparent cells through which light can pass. This layer is only present in the palms of the hands and soles of the feet.  Granular layer – this layer is usually 1-3 layers thick. The cells have distinct granules and keratin is produced in this Epidermis  layer. Prickle cell layer – this layer is 3-6 layers thick and the cells are constantly dividing.  Germinating layer – a single basal layer of cells, that contain the pigment melanin. The cells of the epidermis are produced in this layer and have a distinct nuclei. These cells divide continuously by a process known as mitosis.  Layer Function Stratum Corneum/ This is the surface layer of skin consisting of 25-30 dead Horny Layer irregular keratinised cells. This layer of skin is waterproof. Desquamation occurs here. Stratum Lucidium/ This layer is 4 cells deep and is narrow and transparent. It is Clear Layer found on the palms of the hands and soles of the feet. Stratum Granulosum/ This layer is between 1 and 3 cells deep. Granules of keratin Granular Layer appear in this layer as the nucleus starts to break down. Stratum Spinosum/ This layer is 8 cells deep with round nucleated cells. They Prickle Cell Layer produce fibrils which interconnect them with neighbouring cells. Stratum Germinativum/ This layer is 1 cell deep, rounded and defined with a nucleus. Basal Layer These epithelial cells divide and reproduce themselves through mitosis. Cells of the epidermis Melanocytes are present in this layer which produce the pigment melanin. Langerhans cells are also present which absorb and remove foreign bodies. Keratinocytes are the primary cell type (about 90%) within the epidermis which is the outermost layer of the skin. Merkel cells – Touch/Sensation Dermis   Papillary Layer – is made up of loose connective tissue. It contains intricate networks of blood and lymphatic capillaries and nerve endings. These networks nourish the lower layers of the epidermis and hair follicles, carry oxygen to the tissues and remove waste from the tissues.  Reticular Layer – The reticular layer is made up of Dermis connective tissue that helps to support the dermis and hold the structures of the dermis in place. It is rich with (True skin) fibroblasts which form collagen and elastin. The later connects the dermis to the subcutaneous layer. Collagen gives the skin a plump and youthful appearance and is a white fibrous tissue. Elastin gives the skin its elastic properties and is made up of yellow elastic tissue. Collagen and elastin are two types of proteins that form the fibrous component of the connective tissue   Fibroblasts – Fibroblasts play an important role in tissue repair following tissue damage. They produce 2 proteins – collagen and elastin. Collagen provides strength and elasticity, and elastin allows the skin to stretch. As we age the production of collagen and elastin slows down. Cells  Mast Cells – Mast cells release histamine in response to damage to local tissues caused by of the infections. Histamine causes blood vessels to become dilated and allows fluid and cells from the immune system to leak out to the site of the Dermis infection to help with the healing process. Heparin which is an anti-coagulant.  Phagocytes – Phagocytes are white blood cells which move through the skin’s tissues destroying pathogens and other cell debris. Subcutaneous layer/Hypodermis   This is located under the dermis and is mainly made up of fat cells (adipose tissue). This fatty layer of the skin provides the plump contours of the body, protection, insulation, support and a food Subcutaneous supply if needed. A certain amount of fat layer/Hypodermis in the face is beneficial as it plumps out the facial contours making the face look more youthful. If a client looses a lot of weight quite rapidly you will notice that they look as though they have aged. Appendages  Sweat glands The sweat glands, which are sometimes referred to as the sudoriferous glands, extend from the epidermis into the dermis and are found all over the body, however they are particularly numerous in the palms of the hands and the soles of the feet They regulate the body temperature by allowing sweat to evaporate from the body. There are two different types of sweat glands:  Eccrine glands – are found all over the body and secrete a watery fluid.  Apocrine glands – are found in the underarms, nipple and groin area and become active at puberty. They secrete a thicker fluid that contains urea, fats, sugars and a small amount of protein. Body odour can occur when bacteria starts to break down the sweat. Hair follicle The hair follicle is an indentation of the epidermis with it’s walls forming a protective layer that houses the hair. Hair shaft The hair shaft is the portion of the hair that lies above the skins surface. It is the visible part that you see such as the eyebrows, eyelashes, body hair and the hair on the head. Dermal papilla The dermal papilla is the blood supply for the hair and its follicle. It provides food and oxygen, which are essential for the growth of the hair. The dermal papilla is a separate organ that serves the follicle; it is not part of the hair. Blood supply Blood is supplied to the skin by small blood vessels known as blood capillaries. All parts of our body require a blood supply as it provides the vital oxygen and nutrients that tissues require in order to survive. The capillaries also remove waste products and toxins from the tissues. The capillaries also help to maintain the body temperature by dilating (widening) and constricting (narrowing). Arrector Pili Muscle This muscle is attached to the hair follicle and it contracts when you are cold or frightened causing the hair to stand up on end. This action traps a layer of warm air around the body to keep the body warm. When the muscles contracts it pulls on the skin around the follicle opening therefore producing goose pimples. Nerve Endings Sensory nerve endings are found in the skin and detect changes in the environment such as heat, cold, touch, pain and pressure. There are different nerve endings that detect the different sensations. Sensory nerve endings send messages to our brain to let us know what we are feeling. https://i.pinimg.com/originals/d7/85/fb/d785fbe8ac5b4665667b2767c3c0b1ad.jpg Sebaceous glands These glands are found all over the body except for the palms of the hands and the soles of the feet and produce the natural oil of the skin - sebum. The sebaceous glands become more active at puberty due to the increased levels of androgens (male hormone) being produced. Men generally secrete more sebum than women, and you will usually note that the sebaceous glands become less active as we get older. Sebum is bactericidal and fungicidal and so prevents against infection, it also provides protection and prevents the skin from drying out.