Skin Flashcards
Key ideas about the skin
- largest organ (12-15%
- barrier to external environment
- insight to internal health, even in adulthood
what are the layers of the skin
Epidermis (uppermost layer)
Dermis
Is hypodermis a layer of the skin? why?
No as it is a layer of tissue that binds skin to underlying tissue
Is the dermis thicker or the epidermis?
Dermis
what are fibroblasts?
Cells that produce the extracellular matrix proteins in the dermis
(main ECM protein is collagen)
What other ECM proteins are produced?
Laminin and fibronectin
What do these ECM proteins do?
they form elastic and reticular fibres
what are the 2 zones within in the dermis?
papillary layer- thin loose connective tissue, movement of leukocytes, mast and macrophage cells
reticular layer- thick dense irregular connective tissue layer, less cells + adipocyte clusters
what are adipocyte clusters?
They are fat cells that cluster together in the reticular layer
*These can cause stretching of skin in individuals with lots of fat
what accessory organs pass through the dermis?
nails, hair, oil + sweat glands
The skin has a rich layer of blood + lymphatic vessels as well as a specialised vessel know as?
arteriovenous anastomoses
Why are arteriovenous anastomoses vessels important?
they are important for thermoregulation
what causes sensitivity within the dermis layer?
nerve endings
what is the structure of the epidermis made of?
keratinised stratified squamous epithelium
what are the 5 layers of the epidermis?
- Stratum Basale
- Stratum spinosum
- Stratum granulosum
- Stratum corneum
5- stratum lucidum (TRANSLUCENT LAYER ONLY IN THICK SKIN THAT PROTECTS FROM MECHANICAL STRESS)
What are the 2 types of skin and how are they different?
Thick- 5 layers, smooth + no hair (palms, feet and fingertips)
Thin- 4 layers
Does the epidermis have any blood vessels?
No
What are the properties of Stratum Basale?
They have:
- keratinocytes- stem cells constantly dividing to replenish the skin (mitotically active)
- Melanocytes- give skin colour
- Tactile/Merkel cells- connected to sensory nerves
Other than melanin, what else gives skin pigmentation?
Blood perfusion
Carotene pigments
what are the 2 types of melanin?
pheomelanin- red/ yellow pigment
eumelanin- brown/ black pigment
What are Melanocytes and how do they work?
They are cells that release Melanin
Melanin is a UV absorbent, antioxidant –> protects skin form UV damage
Melanosomes produced by melanocytes are phagocytosed by Keratinocytes –> these then surround the nucleus on the sun side for protection
What are the types of wavy boundry in the skin?
- Dermal papillae - raised areas eg fingerprint (the ones going up)
- Epidermal (rete) ridges (the ones going down)
- These prevent the sliding of layers - providing high degree of mechanical stress
What are the properties of the Stratum Spinosum?
-Several keratinocyte layers
-Usually thickest layer (except in thick skin = stratum corneum)
-Deepest cells are mitotic - and they are pushed upwards –> cease to divide (stops dividing)
-As they go on this journey, they produce Keratin filaments –> flatten more in upper layers
-KERATINOCYTES ARE STRONGLY LINKED BY DESMOSOMES
-TIGHT JUNCTION ENSURE WATER RETENTION OF SKIN
-DENDRITIC CELLS PRESENT
What are the properties of Stratum Granulosum?
-3-5 layers o flat keratinocytes (more present in thick skin than thin skin)
-Post-mitotic, tight junction claudins - important barrier function
-contain dark-staining granules - bind to cytoskeleton
cells undergo apoptosis - programmed cell death
-produce glycolipid-filled vesicles - these spread over the surface of this layer and form a waterproof barrier between stratum spinosum
