The Skin
Know Your Skin
The skin has two main layers, the epidermis and dermis.
Below these is a layer of subcutaneous (under the skin) fat.
The epidermis
The outer surface of the skin is the epidermis, which itself contains
several layers the basal cell layer, the spinous cell layer, the
granular cell layer, and the stratum corneum. The cells in the
epidermis are called keratinocytes.
The deepest layer of the epidermis is the basal cell
layer. Here cells are continually dividing to produce
plump new skin cells (millions daily). These cells move
towards the skin surface, pushed upward by the
dividing cells below them.
Blood vessels in the dermis which is below the basal
cell layer supply nutrients to support this active growth
of new skin cells. As the basal cells move upwards and
away from their blood supply, their cell content and shape
change, as follows.
Cells above the basal cell layer become more irregular in
shape and form the spinous layer. Above this, cells move into the
granular layer. Being distant from the blood supply in the dermis, the cells begin to flatten and die and accumulate a substance called keratin. Keratin is a protein that is also found in hair and nails.
Below these is a layer of subcutaneous (under the skin) fat.
The epidermis
The outer surface of the skin is the epidermis, which itself contains
several layers the basal cell layer, the spinous cell layer, the
granular cell layer, and the stratum corneum. The cells in the
epidermis are called keratinocytes.
The deepest layer of the epidermis is the basal cell
layer. Here cells are continually dividing to produce
plump new skin cells (millions daily). These cells move
towards the skin surface, pushed upward by the
dividing cells below them.
Blood vessels in the dermis which is below the basal
cell layer supply nutrients to support this active growth
of new skin cells. As the basal cells move upwards and
away from their blood supply, their cell content and shape
change, as follows.
Cells above the basal cell layer become more irregular in
shape and form the spinous layer. Above this, cells move into the
granular layer. Being distant from the blood supply in the dermis, the cells begin to flatten and die and accumulate a substance called keratin. Keratin is a protein that is also found in hair and nails.
skin
(skin) n 1.a. the tissue forming the outer covering of the
vertebrate body: it consists of two layers.
The
stratum corneum (horny layer) is the top layer of the epidermis it is the layer
of the skin that we see from the outside. Cells here are flat and scale-like
(squamous) in shape. These cells are dead, contain a lot of keratin and are
arranged in overlapping layers that impart a tough and waterproof character to
the skins surface.
Dead skin cells are continually shed from the skins surface. This is balanced by the dividing cells in the basal cell layer to produce a state of constant renewal. Also in the basal cell layer are cells called melanocytes that produce melanin. Melanin is a pigment that is absorbed into the dividing skin cells to help protect them against damage from sunlight (ultraviolet light). The amount of melanin in your skin is determined by your genes and by how much exposure to sunlight you have. The more melanin pigment present, the darker the colour of your skin.
The epidermis also contains dendritic (Langerhans) cells, which are part of the immune system and help protect the body from foreign substances.
The dermis
Below the epidermis is the layer called the dermis. The top layer of the dermis the one directly below the epidermis has many ridges called papillae. On the fingertips, the skins surface follows this pattern of ridges to create our individual fingerprints. So the ridges are not on the outermost layer of skin, as it might appear.
The dermis contains a variable amount of fat, and also collagen and elastin fibres which provide strength and flexibility to the skin. In an older person the elastin fibres fragment and much of the skins elastic quality is lost. This, along with the loss of subcutaneous fat, results in wrinkles.
When the skin is exposed to sunlight, modified cholesterol in the dermis produces vitamin D, which helps the body to absorb calcium for healthy bones.
Here are some of the other structures within the dermis that enhance the skins function.
Dead skin cells are continually shed from the skins surface. This is balanced by the dividing cells in the basal cell layer to produce a state of constant renewal. Also in the basal cell layer are cells called melanocytes that produce melanin. Melanin is a pigment that is absorbed into the dividing skin cells to help protect them against damage from sunlight (ultraviolet light). The amount of melanin in your skin is determined by your genes and by how much exposure to sunlight you have. The more melanin pigment present, the darker the colour of your skin.
The epidermis also contains dendritic (Langerhans) cells, which are part of the immune system and help protect the body from foreign substances.
The dermis
Below the epidermis is the layer called the dermis. The top layer of the dermis the one directly below the epidermis has many ridges called papillae. On the fingertips, the skins surface follows this pattern of ridges to create our individual fingerprints. So the ridges are not on the outermost layer of skin, as it might appear.
The dermis contains a variable amount of fat, and also collagen and elastin fibres which provide strength and flexibility to the skin. In an older person the elastin fibres fragment and much of the skins elastic quality is lost. This, along with the loss of subcutaneous fat, results in wrinkles.
When the skin is exposed to sunlight, modified cholesterol in the dermis produces vitamin D, which helps the body to absorb calcium for healthy bones.
Here are some of the other structures within the dermis that enhance the skins function.
•
WHERE ARE THE NERVE ENDINGS SITUATED?
• NAME THE 5 LAYERS OF THE EPIDERMIS.
1. The Stratum Corneum (Horny Layer).
• This layer consists of tightly packed scale like cells continually shedding and replaced.
These cells develop from underneath layers, they form keratin which acts as a waterproof covering for the skin.
2. The Stratum Lucidum (Clear Layer).
• Consists of small transparent cells through which light can pass.
3. The Stratum Mucosum ( Pricle Cell Layer).
• Tissue fluid is stored in this layer.
4. The Stratum Granulosum (Granular Layer).
• Consists of cells that look like distinct granules. These cells undergo a change into a horny substance (keratin).
5. The Stratum Germinativium ( Basal or Mother Cell Layer).
• These cells are responsible for the growth of the epidermis.
It also contains a dark pigment called melanin, which protects the sensitive cells below the dermis
from the destructive effect of excessive ultra violet rays of the sun.
• WHAT CELL IS RESPONSIBLE FOR THE BROWN PIGMENT?
The cell is Melanocyte (in the Epidermis). This is the cell that contains melanin or colour pigment.
• HOW LONG DOES IT TAKE FOR BASAL CELL TO REACH THE KERATIN STAGE?
From the time that the basal cell is formed to the stage of being keratin is approximately 28 days,
• WHAT ARE THE FUNCTIONS OF THE SKIN?
1. Protection
2. Perception
3. Excretion
• NAME THE THREE GLANDS SITUATED IN THE DERMIS?
Skin Types and Typical Elements of the Skin
DRY SKIN
1. THE LINES – The normal lines of the skin are numerous and form a rather dense network.
Some of these lines have irregular edges and begin to look like feathers which are a sign of
superficial dehydration often due to exterior agents ( central heating, wind).
2. THE SKIN – The thin skin is normally puffy. In some places it shows small cracks and tiny lines
which are always a sign of dehydration.
3. THE TINY WRINKLES – Following this slight dehydration, the skin retracts and strial crossing of lines
give the appearance of a feather. They are forming lines. These strial some times cross.
4. THE PORES – The pores are usually rather small.
5. THE BLACK SPOTS – are usually due to flakes of dry cells.
EXPRESSION LINES
• Expression lines visible to the naked eye appear on the imprint like many deep strial.
OILY SKIN
• Is usually shiny, thick and show blackheads. Also has a tendency to acne. The pores are usually open and full.
NORMAL SKIN
• Is neither too dry nor to oily; is well hydrated and has a tendency to go dry or oily.
DEHYDRATED SKIN
• Has the same type as oily skin. Only the pores are opened and empty. When you look at the skin there are holes.
THERE ARE 3 DEGREES OF DEHYDRATION.
1. CRISS CROSS – Lines going horizontal and vertical over the face
2. VERTICAL – Lines going down the face when smiling
3. HORIZONTAL - Placing your finger lightly on the face and pushing up slightly, there are fine lines going across.
DRY DEHYDRATED SKIN
• Is the same as the dry skin; it is fine, the pores are invisible, its not shiny and has exactly the same 3 degrees as oily dehydrated.
HYDRATED SKIN
• The skin is round and taut and holds water inside the skin.
When a person with this skin is 30 years old, she will have hardly any wrinkles.
• NAME THE 5 LAYERS OF THE EPIDERMIS.
1. The Stratum Corneum (Horny Layer).
• This layer consists of tightly packed scale like cells continually shedding and replaced.
These cells develop from underneath layers, they form keratin which acts as a waterproof covering for the skin.
2. The Stratum Lucidum (Clear Layer).
• Consists of small transparent cells through which light can pass.
3. The Stratum Mucosum ( Pricle Cell Layer).
• Tissue fluid is stored in this layer.
4. The Stratum Granulosum (Granular Layer).
• Consists of cells that look like distinct granules. These cells undergo a change into a horny substance (keratin).
5. The Stratum Germinativium ( Basal or Mother Cell Layer).
• These cells are responsible for the growth of the epidermis.
It also contains a dark pigment called melanin, which protects the sensitive cells below the dermis
from the destructive effect of excessive ultra violet rays of the sun.
• WHAT CELL IS RESPONSIBLE FOR THE BROWN PIGMENT?
The cell is Melanocyte (in the Epidermis). This is the cell that contains melanin or colour pigment.
• HOW LONG DOES IT TAKE FOR BASAL CELL TO REACH THE KERATIN STAGE?
From the time that the basal cell is formed to the stage of being keratin is approximately 28 days,
• WHAT ARE THE FUNCTIONS OF THE SKIN?
1. Protection
2. Perception
3. Excretion
• NAME THE THREE GLANDS SITUATED IN THE DERMIS?
Skin Types and Typical Elements of the Skin
DRY SKIN
1. THE LINES – The normal lines of the skin are numerous and form a rather dense network.
Some of these lines have irregular edges and begin to look like feathers which are a sign of
superficial dehydration often due to exterior agents ( central heating, wind).
2. THE SKIN – The thin skin is normally puffy. In some places it shows small cracks and tiny lines
which are always a sign of dehydration.
3. THE TINY WRINKLES – Following this slight dehydration, the skin retracts and strial crossing of lines
give the appearance of a feather. They are forming lines. These strial some times cross.
4. THE PORES – The pores are usually rather small.
5. THE BLACK SPOTS – are usually due to flakes of dry cells.
EXPRESSION LINES
• Expression lines visible to the naked eye appear on the imprint like many deep strial.
OILY SKIN
• Is usually shiny, thick and show blackheads. Also has a tendency to acne. The pores are usually open and full.
NORMAL SKIN
• Is neither too dry nor to oily; is well hydrated and has a tendency to go dry or oily.
DEHYDRATED SKIN
• Has the same type as oily skin. Only the pores are opened and empty. When you look at the skin there are holes.
THERE ARE 3 DEGREES OF DEHYDRATION.
1. CRISS CROSS – Lines going horizontal and vertical over the face
2. VERTICAL – Lines going down the face when smiling
3. HORIZONTAL - Placing your finger lightly on the face and pushing up slightly, there are fine lines going across.
DRY DEHYDRATED SKIN
• Is the same as the dry skin; it is fine, the pores are invisible, its not shiny and has exactly the same 3 degrees as oily dehydrated.
HYDRATED SKIN
• The skin is round and taut and holds water inside the skin.
When a person with this skin is 30 years old, she will have hardly any wrinkles.
•
Blood vessels supply nutrients to the dividing cells in the basal layer and
remove any waste products. They also help maintain body temperature by dilating
and carrying more blood when the body needs to lose heat from its surface; they
narrow and carry less blood when the body needs to limit the amount of heat
lost at its surface.
• Specialised nerves in the dermis detect heat, cold, pain, pressure and touch and relay this information to the brain. In this way the body senses changes in the environment that may potentially harm the body.
• Hair follicles are embedded in the dermis and occur all over the body, except on the soles, palms and lips. Each hair follicle has a layer of cells at its base that continually divides, pushing overlying cells upwards inside the follicle. These cells become keratinised and die, like the cells in the epidermis, but here form the hair shaft that is visible above the skin. The colour of the hair is determined by the amount and type of melanin in the outer layer of the hair shaft.
• A sebaceous (oil) gland opens into each hair follicle and produces sebum, a lubricant for the hair and skin that helps repel water, damaging chemicals and microorganisms (germs).
• Attached to each hair follicle are small erector pili muscle fibres. These muscle fibres contract in cold weather and sometimes in fright this pulls the hair up which pulls on the skin with the result being goosebumps.
• Sweat glands occur on all skin areas each person has more than 2 million. When the body needs to lose heat these glands produce sweat (a mix of water, salts and some waste material such as urea). Sweat moves to the skins surface via the sweat duct, and evaporation of this water from the skin has a cooling effect on the body. The skin varies in thickness and the number of hair follicles, sebaceous glands and sweat glands in different areas of the body. The thickest skin is on the soles of the feet and the palms of the hands. A large number of hair follicles are on the top of the head.
• Specialised nerves in the dermis detect heat, cold, pain, pressure and touch and relay this information to the brain. In this way the body senses changes in the environment that may potentially harm the body.
• Hair follicles are embedded in the dermis and occur all over the body, except on the soles, palms and lips. Each hair follicle has a layer of cells at its base that continually divides, pushing overlying cells upwards inside the follicle. These cells become keratinised and die, like the cells in the epidermis, but here form the hair shaft that is visible above the skin. The colour of the hair is determined by the amount and type of melanin in the outer layer of the hair shaft.
• A sebaceous (oil) gland opens into each hair follicle and produces sebum, a lubricant for the hair and skin that helps repel water, damaging chemicals and microorganisms (germs).
• Attached to each hair follicle are small erector pili muscle fibres. These muscle fibres contract in cold weather and sometimes in fright this pulls the hair up which pulls on the skin with the result being goosebumps.
• Sweat glands occur on all skin areas each person has more than 2 million. When the body needs to lose heat these glands produce sweat (a mix of water, salts and some waste material such as urea). Sweat moves to the skins surface via the sweat duct, and evaporation of this water from the skin has a cooling effect on the body. The skin varies in thickness and the number of hair follicles, sebaceous glands and sweat glands in different areas of the body. The thickest skin is on the soles of the feet and the palms of the hands. A large number of hair follicles are on the top of the head.
Common
Questions
• WHAT IS THE SKIN?
It is the largest organ of the body, essential to health and life.
• NAME THE 3 LAYERS OF THE SKIN STRUCTURE.
1. Epidermis or Cuticle.
2. Dermis or True Skin.
3. Subcutaneous Tissue or Hypodermis.
• WHERE ARE THE SEBACIOUS GLANDS ( Oil Glands)?
The Dermis layer contains glands. The first of these is the Sebacious Glands which are situated at the side of the hair shaft. There is a greater percentage of oil glands on the forehead, nose and chin area, and behind the ear.
• WHERE ARE THE CAPILARIES?
In the Dermis layer, they are situated just beneath the Dermo-Epidermal junction.
• WHAT IS THE SKIN?
It is the largest organ of the body, essential to health and life.
• NAME THE 3 LAYERS OF THE SKIN STRUCTURE.
1. Epidermis or Cuticle.
2. Dermis or True Skin.
3. Subcutaneous Tissue or Hypodermis.
• WHERE ARE THE SEBACIOUS GLANDS ( Oil Glands)?
The Dermis layer contains glands. The first of these is the Sebacious Glands which are situated at the side of the hair shaft. There is a greater percentage of oil glands on the forehead, nose and chin area, and behind the ear.
• WHERE ARE THE CAPILARIES?
In the Dermis layer, they are situated just beneath the Dermo-Epidermal junction.
Subcutaneous
fat
The innermost layer of the skin is the layer of subcutaneous fat, and its thickness varies in different regions of the body. The fat stored in this layer represents an energy source for the body and helps to insulate the body against changes in the outside temperature.
Functions of the skin
As you can see, there are many different structures within the skin. Together these structures impart many protective properties to the skin that help avoid damage to the body from outside influences. In this way, the skin:
• protects the body from water loss and from injury due to bumps, chemicals, sunlight or microorganisms (germs); • helps to control body temperature;
• is a sensor to inform the brain of changes in the immediate environment; and
• synthesises vitamin D.
The innermost layer of the skin is the layer of subcutaneous fat, and its thickness varies in different regions of the body. The fat stored in this layer represents an energy source for the body and helps to insulate the body against changes in the outside temperature.
Functions of the skin
As you can see, there are many different structures within the skin. Together these structures impart many protective properties to the skin that help avoid damage to the body from outside influences. In this way, the skin:
• protects the body from water loss and from injury due to bumps, chemicals, sunlight or microorganisms (germs); • helps to control body temperature;
• is a sensor to inform the brain of changes in the immediate environment; and
• synthesises vitamin D.
