PSP1- UNIT 9
INTEGUMENTARY &
MUSCULOSKELETAL
SYSTEMS
, Integumentary system
Structure and function of skin
Epidermis:
● Outermost layer
● Covers whole body
● Protects dermis
● 4 main layers:
1) Stratum basale
2) Stratum spinosum
3) Stratum granulosum
4) Stratum corneum
● Avascular
● Keratinocytes= develop from stem cells in basale which produces and stores
keratin
● Keratinocytes produce keratin and profilaggrin
● Profilaggrin breaks down filaggrin
● Filaggrin= further broken down into NMF
● Stratum corneum is water impermeable
● It is strengthened by corneodesmosomes
Extra layer:
● 5th epidermal layer called stratum lucidum.
, ● Located between granulosum and corneum
● It consists of 3 to 5 layers of dead cells
● Present in areas of thick skin such as the palms, soles and fingers
● cells are filled with eleidin
Cells present in the epidermis
● Melanocytes: dendritic cells in stratum basale
● Produce melanin which protects against UV radiation
● Melanocytes contain melanosomes where melanin is synthesised
● Pheomelanin: red to yellow colour
● Eumelanin: dark brown to black
● Langerhan cells: dendritic cells in stratum spinosum
● First line of immunological defense
● Merkel cells: non dendritic, non keratinocytic, found in stratum basale.
● Function as mechanoreceptors
Dermis:
● Contains blood vessels, sensory nerves, lymphatic vessels
● 2 layers:
- Papillary: blood vessels that supply nutrients and oxygen to cells of
epidermis
- Contains meissner's corpuscles which are responsible for sensing
touch, pain and temp
- Reticular: Deeper layer of dermis which is thicker
- Consists of collagen, elastin and glycosaminoglycans (GAGs)
● Collagen:
- Fibrous protein
- found in other tissues such as tendons, ligaments, bones and teeth
- provides tensile strength to the dermis
- Collagen production declines with age so that the wrinkling and
sagging observed in aged skin is partly due to both damaged collagen
and a slower rate of production of new collagen
● Elastin:
- Fibrous protein
- providing resilience and suppleness, restoring the skin to its initial
shape after stretching
● GAGs:
- polysaccharides containing sugar and protein
INTEGUMENTARY &
MUSCULOSKELETAL
SYSTEMS
, Integumentary system
Structure and function of skin
Epidermis:
● Outermost layer
● Covers whole body
● Protects dermis
● 4 main layers:
1) Stratum basale
2) Stratum spinosum
3) Stratum granulosum
4) Stratum corneum
● Avascular
● Keratinocytes= develop from stem cells in basale which produces and stores
keratin
● Keratinocytes produce keratin and profilaggrin
● Profilaggrin breaks down filaggrin
● Filaggrin= further broken down into NMF
● Stratum corneum is water impermeable
● It is strengthened by corneodesmosomes
Extra layer:
● 5th epidermal layer called stratum lucidum.
, ● Located between granulosum and corneum
● It consists of 3 to 5 layers of dead cells
● Present in areas of thick skin such as the palms, soles and fingers
● cells are filled with eleidin
Cells present in the epidermis
● Melanocytes: dendritic cells in stratum basale
● Produce melanin which protects against UV radiation
● Melanocytes contain melanosomes where melanin is synthesised
● Pheomelanin: red to yellow colour
● Eumelanin: dark brown to black
● Langerhan cells: dendritic cells in stratum spinosum
● First line of immunological defense
● Merkel cells: non dendritic, non keratinocytic, found in stratum basale.
● Function as mechanoreceptors
Dermis:
● Contains blood vessels, sensory nerves, lymphatic vessels
● 2 layers:
- Papillary: blood vessels that supply nutrients and oxygen to cells of
epidermis
- Contains meissner's corpuscles which are responsible for sensing
touch, pain and temp
- Reticular: Deeper layer of dermis which is thicker
- Consists of collagen, elastin and glycosaminoglycans (GAGs)
● Collagen:
- Fibrous protein
- found in other tissues such as tendons, ligaments, bones and teeth
- provides tensile strength to the dermis
- Collagen production declines with age so that the wrinkling and
sagging observed in aged skin is partly due to both damaged collagen
and a slower rate of production of new collagen
● Elastin:
- Fibrous protein
- providing resilience and suppleness, restoring the skin to its initial
shape after stretching
● GAGs:
- polysaccharides containing sugar and protein
