The skin consists of two main layers. The epidermis (the outer layer) and the dermis, which is the inner layer. Beneath the dermis is a fatty subcutaneous layer which, in most parts of the body, loosely attach the skin to the underlying muscle. In the scalp however, a strong shaft of fibrous tissue or tendon called Epioranial Aponeurosis lies immediately below the subcutaneous tissue. The boundary between the epidermis and dermis is Clearly defined, buttne dermis merges gradually with the subcutaneous layer, varying amounts of fat stored in the subcutaneous tissue, acts as insulation to prevent loss of body neat. The surface of the skin and hair is coated with the slightly acid secretion of two types of glands.
A) Sweat glands are coiled tubes lying in the dermis with a duct leading to an opening or pore on the surface of the skin. Sweat consists of 98% water and 2% Sodium Chloride (common salt) with traces of many other substances. The liquid sweat takes heat from the body when it evaporates and this Cools the body.
B) Sebaceous glands are small, sacculated and lodged in the substance of the dermis. They are found in most parts of the skin, but especially abundant in the scalp and face.
They open into the hair follicle and secrete an oily substance called Sebum, which lubricates the skin and hair shaft, so helping to make them Waterproof. Sebum gives lustre to the hair, though excess makes the hair greasy. The secretory activity of the sebaceous gland does not appear to be under nervous control. It is stimulated by hormonal action particularly androgen (male hormones).
The skin is Composed of several layers of cells and the lower the layer the more active the cells. The top layer of skin is the final result of the cells activity below. The top layer of skin is called the EPIDERMlS. It is the outer covering of the skin and is divided into several layers. The cells of the top Skin are hard and horny and are arranged in an overlapping manner, known as the HORNY LAYER. There is little elasticity or colour in these cells and the uppermost are in the process of falling from the skin. Flat dead cells of keratin which are gradually shed from the surface of the skin by friction as for example, when scales are removed from the scalp during brushing. When the skin is wrapped in a bandage for a long time, the dead cells may be seen on its removal as white flakes or strips of dead skin. It is the part of the skin, which is constantly being washed, rubbed or worn away.
Below the horny layer is the CLEAR layer. The flattened cells of this layer contain keratin and have no nuclei, melanin granules are destroyed in this layer of colourless cells. Sunlight penetrates through this layer and activates temporary skin colour.
The GRANULAR layer lays beneath the clear layer. It is composed of layers of granulated cells which are softer than the hard cells above. The nuclei of the cells, in this layer are breaking down leading to the death of the cells. Also, keratin are being formed in the Cells. Keratin is a fibrous sulphur containing protein.
The next layer is composed of a mixture of cell types and is known by several names, the most common being the PRICKLE CELL LAYER. In the lower parts of this layer are found the cells which Contain the natural Colour pigment. Some of the soft nucleated cells of this layer have a spiny outgrowth through which it is thought that melanin granules enter the cells.
Together with the germinating layer it forms the living part of the epidermis. The GERMINATING LAYER is the lowest part of the epidermis. It is sometimes called the base layer. This is formed of larger cells which line the wavy base of the epidermis. This actively growing layer consists of regularly arranged cells which are Constantly dividing to form new Cells, so pushing the old Cells towards the surface of the skin. The germinating layer is continuous around the hair follicles, sebaceous glands and sweat glands, and although these structures may appear to be part of the dermis they are all down growths of the epidermis. Among the cells of this layer are smaller cells called melanocytes. Which produce the pigment of the skin, in the form of black, brown or yellow granules of melanin. Sunbathing increases the production of melanin which protects the skin from damage by the sun’s rays. The dark pigment absorbs harmful radiation. There is no blood or nerve supply to the epidermis, all nutrients come from below.
The DERMIS joins the epidermis in a series of ridges called dermal papillae, which are shallow in the scalp. The dermis is the largest section of the skin, and is abundantly supplied with blood and nerve vessels which take nourishment to the growing cells of the epidermis. The blood vessels also help to keep the body temperature constant, by dilating if the body is too not and constricting if the body is too cold. It also contains units of touch, heat, cold and pain in its upper regions. The dermis is between 1 mm and 4mm in thickness and consists of a dense network of fibres embedded in a jelly like ground substance. Many of the fibres are elastic fibres and give the skin flexibility the ground substance holds a lot of water which makes the skin firm.
Underlying the dermis is the subcutaneous tissue. This is a compound of loose cellular and fatty tissue. This part of the skin stores fat, and gives firmness and roundness to the body’s shapes. It assists in temperature regulation and acts as a protective cushion.
In an unborn child the formation of the hair in the skin initially takes place by a down growth of the epidermis and an upgrowth from the area which is to become the papillae and the germinal matrix the outside of the follicle being a continuation of tine germinating layer of the epidermis. The walls of the follicle are known as the outer root sheath. The dermis forms a protective sheath of connective tissue round each follicle and also projects upwards at the base of the follicle forming the hair papilla.
The hair grows from the epidermal cells surrounding the papilla. The Cells are being nourished from the blood vessels which enter the papilla. Each hair follicle has a muscle, Called the arrector pili muscle. In certain conditions, cold or fear cause the muscle to contract. Moving the sloping follicle and making the hair stand erect, long hair will not appear to stand on end. This muscle contraction is an attempt by the body to trap a layer of still air between the skin and hair to prevent heat loss. Whilst in the follicle, the hair itself is surrounded and protected by the inner root sheath, which grows alongside the hair. The inner root sheath Consists of three layers.
(A) A Cuticle with overlapping scales pointing to the base of the follicle and so over-locking with the Cuticle of the hair and holding the hair firmly.
(B) HUXLEY’S layer, two or three Cells in thickness.
(C) HENLE’S layer, of one cell in thickness which lies next to, but separate from the outer root sheath
The surface of Henle’s layer is smooth and easily able to slip over the outer sheath, as the hair and its inner root sheath move upwards together. The inner root sheath breaks down about two thirds of the Way up the follicle at the level of the opening of the sebaceous glands, the passage of hair along the remaining part of the follicle is eased by the presence of Sebum. If a hair is pulled from the scalp the inner root sheath Comes out at the same time and can be seen as a White thickening at the end of the hair. The lower part of the follicle widens out into the hair bulb which fits over the papilla. The epidermal cells surrounding the papilla form the germinal matrix of the root of hair. These cells are constantly dividing to make new cells which push the older ones upwards.
At first all the cells are alike, but as they move up the follicle they begin to change shape and keratin develops in the cells. The different types of cell for cuticle, cortex and medulla of the hair and the cells of the inner root sheath develop. By the time they are about one third of the way up the follicle cells are dead and fully keratinised. Between the cells surrounding the papilla are melanocytes producing melanin, the Colour of the hair, most of which passes into the cortex of the hair.
The skin is Composed of several layers of cells and the lower the layer the more active the cells. The top layer of skin is the final result of the cells activity below. The top layer of skin is called the EPIDERMlS. It is the outer covering of the skin and is divided into several layers. The cells of the top Skin are hard and horny and are arranged in an overlapping manner, known as the HORNY LAYER. There is little elasticity or colour in these cells and the uppermost are in the process of falling from the skin. Flat dead cells of keratin which are gradually shed from the surface of the skin by friction as for example, when scales are removed from the scalp during brushing. When the skin is wrapped in a bandage for a long time, the dead cells may be seen on its removal as white flakes or strips of dead skin. It is the part of the skin, which is constantly being washed, rubbed or worn away.
Below the horny layer is the CLEAR layer. The flattened cells of this layer contain keratin and have no nuclei, melanin granules are destroyed in this layer of colourless cells. Sunlight penetrates through this layer and activates temporary skin colour.
The GRANULAR layer lays beneath the clear layer. It is composed of layers of granulated cells which are softer than the hard cells above. The nuclei of the cells, in this layer are breaking down leading to the death of the cells. Also, keratin are being formed in the Cells. Keratin is a fibrous sulphur containing protein.
The next layer is composed of a mixture of cell types and is known by several names, the most common being the PRICKLE CELL LAYER. In the lower parts of this layer are found the cells which Contain the natural Colour pigment. Some of the soft nucleated cells of this layer have a spiny outgrowth through which it is thought that melanin granules enter the cells.
Together with the germinating layer it forms the living part of the epidermis. The GERMINATING LAYER is the lowest part of the epidermis. It is sometimes called the base layer. This is formed of larger cells which line the wavy base of the epidermis. This actively growing layer consists of regularly arranged cells which are Constantly dividing to form new Cells, so pushing the old Cells towards the surface of the skin. The germinating layer is continuous around the hair follicles, sebaceous glands and sweat glands, and although these structures may appear to be part of the dermis they are all down growths of the epidermis. Among the cells of this layer are smaller cells called melanocytes. Which produce the pigment of the skin, in the form of black, brown or yellow granules of melanin. Sunbathing increases the production of melanin which protects the skin from damage by the sun’s rays. The dark pigment absorbs harmful radiation. There is no blood or nerve supply to the epidermis, all nutrients come from below.
The DERMIS joins the epidermis in a series of ridges called dermal papillae, which are shallow in the scalp. The dermis is the largest section of the skin, and is abundantly supplied with blood and nerve vessels which take nourishment to the growing cells of the epidermis. The blood vessels also help to keep the body temperature constant, by dilating if the body is too not and constricting if the body is too cold. It also contains units of touch, heat, cold and pain in its upper regions. The dermis is between 1 mm and 4mm in thickness and consists of a dense network of fibres embedded in a jelly like ground substance. Many of the fibres are elastic fibres and give the skin flexibility the ground substance holds a lot of water which makes the skin firm.
Underlying the dermis is the subcutaneous tissue. This is a compound of loose cellular and fatty tissue. This part of the skin stores fat, and gives firmness and roundness to the body’s shapes. It assists in temperature regulation and acts as a protective cushion.
In an unborn child the formation of the hair in the skin initially takes place by a down growth of the epidermis and an upgrowth from the area which is to become the papillae and the germinal matrix the outside of the follicle being a continuation of tine germinating layer of the epidermis. The walls of the follicle are known as the outer root sheath. The dermis forms a protective sheath of connective tissue round each follicle and also projects upwards at the base of the follicle forming the hair papilla.
The hair grows from the epidermal cells surrounding the papilla. The Cells are being nourished from the blood vessels which enter the papilla. Each hair follicle has a muscle, Called the arrector pili muscle. In certain conditions, cold or fear cause the muscle to contract. Moving the sloping follicle and making the hair stand erect, long hair will not appear to stand on end. This muscle contraction is an attempt by the body to trap a layer of still air between the skin and hair to prevent heat loss. Whilst in the follicle, the hair itself is surrounded and protected by the inner root sheath, which grows alongside the hair. The inner root sheath Consists of three layers.
(A) A Cuticle with overlapping scales pointing to the base of the follicle and so over-locking with the Cuticle of the hair and holding the hair firmly.
(B) HUXLEY’S layer, two or three Cells in thickness.
(C) HENLE’S layer, of one cell in thickness which lies next to, but separate from the outer root sheath
The surface of Henle’s layer is smooth and easily able to slip over the outer sheath, as the hair and its inner root sheath move upwards together. The inner root sheath breaks down about two thirds of the Way up the follicle at the level of the opening of the sebaceous glands, the passage of hair along the remaining part of the follicle is eased by the presence of Sebum. If a hair is pulled from the scalp the inner root sheath Comes out at the same time and can be seen as a White thickening at the end of the hair. The lower part of the follicle widens out into the hair bulb which fits over the papilla. The epidermal cells surrounding the papilla form the germinal matrix of the root of hair. These cells are constantly dividing to make new cells which push the older ones upwards.
At first all the cells are alike, but as they move up the follicle they begin to change shape and keratin develops in the cells. The different types of cell for cuticle, cortex and medulla of the hair and the cells of the inner root sheath develop. By the time they are about one third of the way up the follicle cells are dead and fully keratinised. Between the cells surrounding the papilla are melanocytes producing melanin, the Colour of the hair, most of which passes into the cortex of the hair.
