Week 1 - Structure and function of the skin Flashcards
What are the 3 main functions of the skin
Protection (both physically and immunologically)
Physiological regulation (body temperature, fluid balance, vitamin D production)
Sensation
What are the 3 main layers of the skin
Epidermis
Dermis
Hypodermis
What is the name of the muscle which attaches to the hair follicle
Arrector pilli
Describe the mechanism by which the arrestor pili warms the body in response to being cold
The muscle contracts to cause the hair to stand on end which traps air and warms the body
Describe the structure of the epidermal epithelial cells
Keratinised stratified squamous epithelium
What are the epithelial cells that make up the epidermis
Keratinocytes
How is the stratum basale layer connected to the basement membrane
By hemidesmosomes (intermediate filament –>extracellular matrix)
How are the epithelial cells joined together in the epidermis
Joined together by desmosome cell–>cell junctions
Name all the layers of epidermis from top to bottom
Stratum Corneum
Stratum Lucidum (areas of thick skin)
Stratum Granulosum
Stratum Spinosum
Stratum basale
What type of cells make up the epidermis
Keratinocytes
What do keratinocytes sit on
The basement membrane
What type of cells do you find in the stratum basale
Stem cells
What is the cell junction between the stem cells and the basement membrane
Hemi-desmasomes
What joins together the epithelial cells
Desmosome cell junctions
Describe the cells in the stratum corneum
Flat, anucleate cells, filled with keratin and lipids, producing a hydrophobic barrier for the skin
What is the extra layer of skin cells found in the epidermis and what is it’s function
The stratum lucidum and it’s role is to reduce abrasion between the stratum corneum and stratum granulosum
Describe the way in which the daughter cells move up the layers of skin
The daughter cells move up from the basale layer and differentiate on their way upwards. 2 weeks to get to the stratum granulosin and 2 weeks to make it up to the top of the stratum corneum?
What type of epithelial tissue is epidermis tissue
Keratinised stratified squamous epithelium
What is the function of the keratinocyte and where found
Provides protection, a barrier and is the site of vitamin D production. Found in the epidermis
What is the function of the stem cells in epidermis and where found
Self renewal and repopulation of epidermal layers
Found in the stratum basale
Function and location of Merkel cell
Found in epidermis and involved in sensation
Function and location of Langerhans cell
Dendritic cell
Antigen presentation phagocytosis. Mainly found in the stratum spinosum
Function and location of the melanocyte
Protection from radiation
Found in the basal layer
Where is melanin made
In melanocyte cells in the melanosomes
How does melanin protect cell from UV
They form a protective layer over the nucleus, thus protecting DNA from damage
Function and location of keratins
Major structural protein and a type of intermediate filament. Found in all epidermal layers
Function and location of profilaggrin granules
Converted to filaggrin which aggregrates keratin filaments into tight bundles. Found in keratohyalin granules
Function and location of involucrin
formation of cell envelope around cells in stratum corneum. Found in keratohyalin granules
Function and location of Loricrin
Cross links to involucrin
Found in keratohylin granules
Function and location of polysaccharides, glycoproteins and lipids
Extrude into intercellular space, form the ‘cement’ that holds together the stratum corneum cells
What type of tissue is the dermis
Connective tissue
What are the main 4 components found in the dermis
Fibroblasts
Collagen type 1
Elastin
Ground substance tissue
What allows the strength in the dermis
Collagen
What allows the stretch in the dermis
Elastin
As you go further down the epidermis, what happens to the strength of collagen and elastin
Collagen gets stronger
Elastin gets less stretchy
Which portion of the dermis has most blood vessels
Outer layer
What do you call the region between the epidermis and the dermis
The dermo-epidermal junction
Function of fibroblast cells
Involved in the synthesis of collagen, elastin and other extracellular matrix components
Function of lymphocytes
immunosurveillance
Function of dermal dendritic cells (langerhan’s cells)
Phagocytosis
Antigen presentation
Functions of mast cells and give examples of substances produced
Produce inflammatory mediators (e.g histamine and heparin)
Produce chemotactic factors for eosinophils and neutrophils
What is the hypodermis composed of
Adipose tissue
What are the 3 main functions of the hypodermis
Energy source
Shock absorption
Insulation
Where do most nerve endings finish
The dermis
When nerve endings finish in the epidermis, into what cells do they extend into
Merkel cells
What are Meissner’s corpuscles
Dermal mechanoreceptors responsible for touch
What are pacinian corpuscles
Hypo-dermal receptor that detects deep pressure and vibration
What are nails composed of
Plates of heavily compacted, heavily keratinised epithelial cells
Name 3 glands found in the skin and describe where they are mainly found
Eccrine glands - found almost everywhere and they excrete sweat
Apocrine gland - armpit sweat?
Sebaceous gland - secrete sebum and are formed from a hair follicle
What are the 3 stages of wound healing
Inflammation
Proliferation
Remodelling
Describe the inflammation stage and for how long this happens
Platelets initiate the blood clot and healing cascade
Neutrophils and basophils are recruited towards the site of injury - red swelling
Neurtophils and macrophages phagocytose the dead tissues and organsims
For 24-48 hours
Describe the proliferative stage
Re-epithelialisation occurs
Within 1/2 days, cell to cell adhesions are loosened and epithelial cells cover the granulation tissue. Granulation tissue forms, mainly made up from type 3 collagen.
Neovascularisation occurs where endothelial cells proliferate
Describe the remodelling phase
- The new granulation tissue becomes mature scar tissue through collagen organising itself into extensively cross-linked bundles
- Collagen type 3 turns into collagen type I
- Final skin strength 70-80% at 1 year
