Skin
Structure of the skin
Epidermis (top layer)
- Stratified epithelium tissue
- 5 layers
1. Stratum corneum- surface layer
- Cells are dead at this stage, they have completely undergone the keratinisation process
- The protoplasm in the cells have completely changes into keratin
- Friction will eventually discard the dead skin cells and they will fall of (desquamation)
2. Stratum lucidum- clear layer
- Water barrier layer, cells have no nucleus
- Cells only have protoplasm in them, making them transparent
- Cells have almost completed the keratinisation process
3. Stratum granulosum- granular layer
- Composed of several layers
- Cells start to undergo major change
- Cells contain keratin
4. Stratum spinosum- prickle cell layer
- Cells are still lobing and contain a nucleus
- Cells are cylindrical/spindle shaped and join to the next cell with a thorn-like process, giving cells a
prickly appearance
5. Stratum germinativum- basal layer
- Primary site of mitosis
- Melanin produced by cells called melanocytes
- Receives nutrients from the papillary layer of the dermis
Melanocytes
- The stratum germinativum layer is a melanocyte, the cells produce pigment granules called melanin
and pass the pigment out through these processes.
- Melanin is made from a protein substance called tyrosine
- Melanin protects the underlying tissues from U.V light and burning, it’s also responsible for the
colour of the skin and any pigment marks
Keratin
- Hard horny substance, which is insoluble in water
- Contains sulphur, this contributes towards the acidic nature of the skin
- It contains two types of protecting coverings for the surface of the skin
1. Hard: found in nails and hair, doesn’t desquamate
2. Soft: found in the epidermis, does desquamate daily
Dermis (middle layer)
- A vascular layer of connective tissue
- Tough elastic layer composed of white fibrous collagen, interlocked with yellow elastic elastin
- Has two layers: Papillary layer and Reticular layer
Papillary layer
- Surface of the dermis layer, interlocks with the stratum germinativum by a series of ridges of
capillary loops.
- These ridges are called papillae, and this is how the stratum germinative receives its blood supply
and gets rid of cellular waste.
- Papillae contains never fibres so allows the sense of touch.
- The papillary layer also contains venous capillaries and lymph vessels
, Reticular layer
- Forms the bulk of the dermis, is tough elastic layer composed of coarse dense fibres, mainly
collagen and elastic fibres.
4 types of cells
Fibroblasts form the production of 3 types of tissue:
1. Areolar tissue: needed for the ground substances of the dermis
2. Collagen
3. Elastin
Mast cells
- Produce histamine as an allergic reaction to heparin
Histiocytes
- Produce histamine as well
Leucocytes
- White blood cells which help fight infection and diseases
Other parts of the skin
Blood supply
- A system of blood vessels including microscopic capillaries which are one cell thick
Lymphatic vessels
- Works in conjunction with the blood supply to carry waste products away from the area
Nerve endings
- Alert the brain and thus the body to heat, cold, pressure and pain
- Part of the defence system of the body
Sweat gland: it contains mainly water, urea and salts. Has two glands:
1. Eccrine
- Excrete watery sweat and control body temperature
- Found in the palms of hands and soles of feet
2. Apocrine
- Excrete milky fluid which when mixed with bacteria on the surface of the skin, produces body odour
- Found in the groin and armpits
Hair follicle
- Travels through the dermis and epidermis
Erector pili muscle
- Are attached to each hair and help with the temperature control of the body pulling the hair
upright, trapping a layer of air causing goosebumps on the skin.
Adipocytes (fat cells)
- Mainly found in the sub-cutis, but some do extend to the dermis
Sebaceous gland
- Connected with hair follicle
- Produces sebum, a fatty acid which keeps the skin moist as it lubricates the hair shaft
- Sweat and sebum forms the acid mantle, this is a protective shield which helps control bacteria
levels and prevents infections and diseases
Subcutaneous layer or Hypodermis (final layer)
Dermal papilla
- Small conical projections at the base of the hair
- Contains blood vessels and nerves which supplies the hair with nutrients
Structure of the skin
Epidermis (top layer)
- Stratified epithelium tissue
- 5 layers
1. Stratum corneum- surface layer
- Cells are dead at this stage, they have completely undergone the keratinisation process
- The protoplasm in the cells have completely changes into keratin
- Friction will eventually discard the dead skin cells and they will fall of (desquamation)
2. Stratum lucidum- clear layer
- Water barrier layer, cells have no nucleus
- Cells only have protoplasm in them, making them transparent
- Cells have almost completed the keratinisation process
3. Stratum granulosum- granular layer
- Composed of several layers
- Cells start to undergo major change
- Cells contain keratin
4. Stratum spinosum- prickle cell layer
- Cells are still lobing and contain a nucleus
- Cells are cylindrical/spindle shaped and join to the next cell with a thorn-like process, giving cells a
prickly appearance
5. Stratum germinativum- basal layer
- Primary site of mitosis
- Melanin produced by cells called melanocytes
- Receives nutrients from the papillary layer of the dermis
Melanocytes
- The stratum germinativum layer is a melanocyte, the cells produce pigment granules called melanin
and pass the pigment out through these processes.
- Melanin is made from a protein substance called tyrosine
- Melanin protects the underlying tissues from U.V light and burning, it’s also responsible for the
colour of the skin and any pigment marks
Keratin
- Hard horny substance, which is insoluble in water
- Contains sulphur, this contributes towards the acidic nature of the skin
- It contains two types of protecting coverings for the surface of the skin
1. Hard: found in nails and hair, doesn’t desquamate
2. Soft: found in the epidermis, does desquamate daily
Dermis (middle layer)
- A vascular layer of connective tissue
- Tough elastic layer composed of white fibrous collagen, interlocked with yellow elastic elastin
- Has two layers: Papillary layer and Reticular layer
Papillary layer
- Surface of the dermis layer, interlocks with the stratum germinativum by a series of ridges of
capillary loops.
- These ridges are called papillae, and this is how the stratum germinative receives its blood supply
and gets rid of cellular waste.
- Papillae contains never fibres so allows the sense of touch.
- The papillary layer also contains venous capillaries and lymph vessels
, Reticular layer
- Forms the bulk of the dermis, is tough elastic layer composed of coarse dense fibres, mainly
collagen and elastic fibres.
4 types of cells
Fibroblasts form the production of 3 types of tissue:
1. Areolar tissue: needed for the ground substances of the dermis
2. Collagen
3. Elastin
Mast cells
- Produce histamine as an allergic reaction to heparin
Histiocytes
- Produce histamine as well
Leucocytes
- White blood cells which help fight infection and diseases
Other parts of the skin
Blood supply
- A system of blood vessels including microscopic capillaries which are one cell thick
Lymphatic vessels
- Works in conjunction with the blood supply to carry waste products away from the area
Nerve endings
- Alert the brain and thus the body to heat, cold, pressure and pain
- Part of the defence system of the body
Sweat gland: it contains mainly water, urea and salts. Has two glands:
1. Eccrine
- Excrete watery sweat and control body temperature
- Found in the palms of hands and soles of feet
2. Apocrine
- Excrete milky fluid which when mixed with bacteria on the surface of the skin, produces body odour
- Found in the groin and armpits
Hair follicle
- Travels through the dermis and epidermis
Erector pili muscle
- Are attached to each hair and help with the temperature control of the body pulling the hair
upright, trapping a layer of air causing goosebumps on the skin.
Adipocytes (fat cells)
- Mainly found in the sub-cutis, but some do extend to the dermis
Sebaceous gland
- Connected with hair follicle
- Produces sebum, a fatty acid which keeps the skin moist as it lubricates the hair shaft
- Sweat and sebum forms the acid mantle, this is a protective shield which helps control bacteria
levels and prevents infections and diseases
Subcutaneous layer or Hypodermis (final layer)
Dermal papilla
- Small conical projections at the base of the hair
- Contains blood vessels and nerves which supplies the hair with nutrients
