Structure and function of Skin Flashcards
What does integument or integumentary system refer to?
Refers to the skin and it’s appendages including hair, nails and glands
Skin is the LARGEST and HEAVIEST organ in the body
What are the main function of skin?
1) Barrier against:
- Dehydration
- Infection
- Injury
- Solar radiation
2) Thermoregulation
3) Sensation
4) Repair
5) Vitamin D production
What are the 3 layers of skin?
- Epidermis
- Dermis
- Hypodermis
Where does the thickness of the epidermis vary?
Thickness varies around the body e.g thin skin on the abdomen and thick skin on the heel of the foot
What are the 4 main layers of the epidermis?
- Stratum basale (basal layer)
- Stratum spinosum (spiny layer)
- Stratum granulosum (granular layer)
- Stratum corneum (cornified layer)
What does the basal layer contain?
Contain the stem cells of skin that constantly proliferate
This layer is attached to the dermis
What does the stratum spinosum have many of?
The cells have many desmosomes visible as spines between cells
What is the stratum granulosum?
1-4 layers of cells containing prominent granules of keratinohyalin (precursor of keratin)
Also contain lamellar bodies which are high in lipids
What do the cell of the stratum granulosum do?
The cells are differentiating to form the outer most protective layer called the stratum corneum
What is the stratum corneum?
It is the outer protective layer of the epidermis
What is the stratum corneum made up of?
Are squamous cells which have lost their nucleus
What does it mean by the stratum corneum being cornified?
Are ‘cornified‘ full of horny keratin (from keratinohyalin granules) that are tough and resistant to injury
What are between the cells in the stratum corneum layer?
Non-polar lipids are between the cells
What are the other epidermal cell types?
- Melanocytes
- Langerhans cells
- Merkel cells
What do melanocytes synthesise?
Synthesise melanosomes and transfer them to basal keratinocytes through long dendrites
How do keratinocytes arrange melanin pigments?
Keratinocytes arrange melanin pigments in a cap distal to the nucleus
What are langerhans cells involved in?
Involved in the immune system as antigen presenting cells
What type of cells are langerhans cells?
Are dendritic cells
Where does vitamin D production occur?
Made in the epidermis, mostly in the basal cells and also stratum spinosum
What does vitamin D production require?
Requires UV light
Where is vitamin D converted into the active form?
Converted to active form in liver and kidney:
-1,25 dihydroxyvitamin D3
What is the dermis?
Is dense, irregular connective tissue
What does collagen in the dermis provide?
Collagen in the dermis provides tensile strength hence protection against abrasion and impact
What does the dermis contain giving its elasticity?
Contains elastin
