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
What are the properties of Stratum Corneum?
-Most superficial (on the surface) - 15-30 layers of dead cornified calls flattened on the surface
-lots of keratins
-enclosed within insoluble amalgam of cross-linked proteins
-surrounded by extracellular lipid envelope (fused lamellar bodies)
-especially resistant to abrasion, penetration and water loss
What are nails and how are they formed?
composed of dead scaly cells densely packed with hard keratin fibers
New cells added by mitosis in the nail matrix
Appearance can indicate underlying conditions - iron deficiency –> flat or concave - long term hypoxemia –> clubbed
What are the three types of barriers in skin protection?
- Physical barrier
- Biochemical barrier
- Immunological barrier
What are the five types of glands found in the skin?
- Eccrine/merocrine sweat glands
- Apocrine sweat glands
- Holocrine sebaceous glands
- Ceruminous glands
- Mammary glands
How do eccrine sweat glands function and what is their
Produce watery perspiration
Controlled by sympathetic nervous system via myoepithelial cells
Primary role in temperature regulation
Release secretions directly to skin surface
What are the characteristics of apocrine sweat glands?
Cells “pinch off” into ducts
Release secretions into hair follicles
Function as scent glands
Respond to stress and sexual stimulation
Located in armpits and genital regions
How do holocrine sebaceous glands work?
Entire cell disintegrates to release product
Produce oily sebum that lubricates skin and hair
Primarily located on face, chest, and back
Differentiated epithelial cells accumulate lipids before rupturing
What immune cells are present in the dermis?
Macrophages and monocytes
Mast cells
Eosinophils
Neutrophils
B and T lymphocytes
What is the role of dermal immune cells?
Tissue remodelling
Repair processes
Tissue proliferation
Release of cytokines and chemokines
Maintain balance in immune response
How does counter current heat exchange work in the skin?
Occurs between arterial and venous blood flow in extremities
Located in dermis
Minimizes heat loss
Important for maintaining core temperature
What is special about blood flow in apical skin?
Contains high density of arteriovenous anastomoses (AVA)
Rich sympathetic innervation using norepinephrine
Core temperature increase → decreased sympathetic tone → increased blood flow
Core temperature decrease → increased sympathetic tone → decreased blood flow
How does non-apical skin regulate temperature?
Uses sympathetic nervous system acetylcholine release
Activates eccrine sweat glands
Releases vasoactive molecules
These molecules relax vascular smooth muscle cells
Results in increased perfusion and heat loss
Which areas of the body are most important for heat exchange?
Areas with high surface area to volume ratio:
Ears
Finger pads
Toes
What characterizes the skin’s microflora?
Contains over 1,000 species
Includes harmless commensals
Contains opportunistic pathogens (e.g., S. aureus)
Plays role in skin defence
