List 6 important functions of skin
- barrier function
- immune recognition and surveillance
- damage repair
- protection from UV radiation
List common functions of skin as a barrier
Regulates water loss
Protect against mechanical, chemical and microbial insults from outside world
Skin deals with innate or adapative immunologic processes?
Fun fact: skin has more lymphocytes than inside the body
Autoimmune bullous diseases are blistering skin diseases mediated by autoantibodies towards what?
skin adhesion molecules (desmosomes, hemidesmosomes)
Characteristic features of autoimmune bulous diseases?
erosions or blisters in skin, often in mucosa
Autoantibodies to hemidesmosomes. Name this skin condition?
Autoantibodies to desmosomes. Name this condition?
Bullous pemphigoid vs Pemphigus vulgaris. Which is which?
Top = Pemphigus vulgaris
Bottom - Bullous pemphigoid
Immunofluorescence. Which is which
Bullous pemphigoid vs pemphigus
Top - Bullous Pempighoid
Bottom - Pemphigus Vulgaris
Impaired wound healing can lead to ?
chronic skin ulcers, risk of infection
Patients can also develop skin lesions bc they become ____ to injury? List 2 examples
Neuropathic ulcers, trigeminal trophic syndrome
Melanin is found where in skin (epidermis/dermis). Purpose of it?
Found in epidermis, protect against UV radiation
Loss of photoprotection increases what 2 OBVIOUS risks?
risk of burning (duh), and skin cancer (duh)
Condition where person has abnormal pigment at birth?
Condition where you lose your pigment as you get older?
Acute effects of UV radiation on skin?
Vitamin D photosynthesis
DNA damage (apoptosis, cell cycle arrest to repair)
What are the 2 chronic effects of UVR on skin?
Photocarcinogenesis (basal cell and squamous cell carcinomas, melanomas)
Term for histologic change that occurs due to chronic UV radiation
Solar elastosis (right picture)
Normal skin (left picture)
Incidence of melanoma in US?
1 in 50
Melanoma more commonly associated with chronic low exposure or acute intense exposure?
Acute intense exposure
Disease of skin that deals with inability to repair DNA?
Xeroderma pigmentosum, DNA excision abnormal
What condition does he have?
Mutation in what gene? Consequence of this?
Hypohidrotic ectodermal dysplasia
Mutation in EDAR (Ectodyplasin A receptor) gene. Protein is critical for proper interaction between developing ectoderm and mesorderm.
Results in abnormal hair follicles, sweat glands, and teeth. Unable to regulate temperature, overheat easily
3 layers of skin?
Epidermis, dermis, subcutis
Cells of epidermis? Which makes up the majority
Keratinocytes (90% of cells), melanocytes, langerhans cells, merkel cells
What cells of epidermis are important when they become malignant?
if you cut your skin, and bleed, what layer of the skin have you at least affected?
Dermis, epidermis has no blood vessels
Dermis or epidermis?
Primarily barrier function, protection, wound healing?
Epidermis sheds itself every ___ days?
14 days to reach stratum corneum
14 days to desquamate
4 Layers of Epidermis?
Stratum corneum, granulosum, spinosum, basale
Function of hemidesmosome?
Connect epidermis to dermis
Epidermis (pink in picture), dermis (blue)
Function of desmosomes?
Keratinocyte to keratinocyte adhesion
What epidermal layer is the source of stem cells?
Division of cells starts in what epidermal layer?
Basal cells (of basal layer) adhere to basement membrane via what?
Cells stop dividing and start terminal differentiation in what epidermal layer?
Lipids begin to develop in what epidermal layer?
Why is the stratum spinosum "spiny"
Due to visible desmosomes with which one KC adheres to another
Profilaggrin synthesis occurs in what epidermal cell layer?
Profilaggrin makes up part of the intracellular keratohyaline granules that are produced in this layer
What layer of the epidermis plays a key role in maintaining a water barrier? How?
- Lipids in lamellar granules secreted into intercellular space to form water barrier to keep water in skin
Nuclei and organelle should degenerate by the time they reach what layer?
Profilaggrin is processed into ____ in the stratum ____? Purpose of this?
filaggrin, stratum corneum
- helps keep water in cells
Stratum corneum creates a protective layer via a combination of what 2 components?
Keratin + filaggrin = macrofibrils (creates protective layer)
Keratin combines to form _____?
Pairs of keratin differ based on what?
location in the body.
Dif keratin pairs in palms/soles vs elsewhere
What amino acid is found in keratin (esp hair and nails)?
Cysteine (which contains sulfur. why your hair smells like shit when it gets burned)
Based on location within body, what layer of the epidermis has different characteristics?
Stratum corneum varies based on different areas within body, such as trunk/back (thinner) vs palms/soles (thicker)
What layer of the epidermis is compared to a brick and mortar wall? What do #s 1 and 2 represent?
1 (bricks) = flattened keratinocytes filled with keratin and filaggrin
2 (mortar) = lipid mixture surrounding keratinocytes, providing water barrier
Name for "pigment producting dendritic cells?"
What pigment is produced?
- produce melanin (a radiation absorbing pigment)
Melanocytes are derived from what embryonic cell lineage?
Neural crest cells, migrat during embryonic development
Where are melanocytes located in the epidermis? What is their ratio to keratinocytes?
"live" along basal cell
1:10 ratio between melanocytes:keratinocytes
In addition to producing melanin, what else do melanocytes do with melanin?
transfers melanin to surrounding keratinocytes
What is classified as the primary defense against UV radiation?
What is this a picture of?
Notice the dendritic like appendages within this diagram, same as picture
Besides melanocytes, name another dendritic cell of the epidermis? Where is its location in the epidermis?
Langerhans cells, found in mid epidermis
Main purpose of Langerhans cells?
Recognize, take up, and present abnormal antigens in skin to lymphocytes in regional lymph nodes
- this abnormal antigen can be a cancerous cell, virally infected cell, chemical allergen (like a fragrance), etc
Name this cell:
Epidermal cell associated with light touch sensation
Merkel cells can develop into what pathologically?
Name 2 cells found in dermis
Fibroblasts, mast cells
Besides fibroblasts/mast cells, what other components are found in dermis?
blood vessels and lymphatics, nerves, sweat and oil glands, hair follicles
3 functions of dermis?
innervation (epidermis has NO innervation or vasculature)
What is considered the primary cell in the dermis? What origin do these cells come from?
Fibroblast, mesenchymal origin
Main purpose of fibroblasts?
- Synthesis and degradation of CT proteins, including collagen, elastin, glycosaminoglycans, and other glycoproteins
- Injury to skin triggers fibroblast mitosis
- Responsible for wound healing and scar formation
What cells in the dermis are rich in histamine and heparin granules?
- release their granules when triggered by injury or when they bind IgE antibodies during allergic reactions
- histamine and other mediators important in allergic reactions and wound healing
Hair follicles stop in dermis or continue into subcutis?
Extend through dermis into subcutis
Each hair follicle is associated with what gland?
sebaceous (oil) gland
What are the 4 components of a pilosebaceous unit?
- Hair follicle
- sebaceous (oil) gland
- apocrine sweat gland (in axilla and anogenital skin)
- arrector pili muscle
"True" sweat glands? Location in body?
Eccrine sweat glands, all over body (as opposed to apocrine found only in axilla/anogenital skin)
Are eccrine sweat glands associated with a hair follice?
Apocrine vs eccrine sweat glands?
- function to regulate temperature by evaporative cooling of sweat?
Eccrine sweat glands
Fat layer found in what layer of skin?
Function of this layer?
insulation, source of energy, protection from injury
Cells/components of subcutis?
fat, blood vessels, fibrous septae
Other than structure, why are fibrous septae important?
B/c the cause cellulite (Fibrous septae pull down in between fat lobules)
OMG I HAVE CELLULITE
Apoptosis is (high or low) in epidermis?
Apoptosis normally low in epidermis, but can increase in some situations
If you get sunburn, what cells in what layer become damaged? Relate this to apoptosis
Sun-damaged cells = damaged keratinocytes in epidermis
Apoptosis will increase (normal response to sun damaged cells)
What happens if apoptosis of sun-damaged cells (keratinocytes) doesnt occur?
Can progress to skin cancer
What disorder is shown in picture?
Associated with genetic defects in what protein?
Atopic dermatitis, defects in filaggrin
What disease is shown here? What mutation is occuring?
Epidermolysis Bullosa Simplex
genetic mutations in Keratin 5/14
Definition of nevus (mole)?
Benign collection of melanocytes
growth of malignant (cancerous) melanocytes