Intro to Skin Flashcards
What are the main skin cells invovled in immune regulation?
Langerhans cells in epidermis, lymphocytes and dermal dendritic cells in dermis
What are the main cells involved in damage repair of the skin? Thermo-reg? Photoprotection?
keratinocyte proliferate in epidemis in response to injury or inflammation, fibroblasts in dermis
Theromreg: vasculature in dermis
Photoprotection: melanocytes
What is this?
Atophic dermatitis
Why is intact skin a poor host for infection?
Skin sheds, the epidermis does not have vessels, and is dry
Skin response to acute sunburn
What is Hypohidrotic ectodermal dysplasia?
This is a genetic condition due to mutations in EDAR gene coding for “ectodyplasin A receptor”, a protein critical for proper interaction between developing ectoderm and mesoderm that results in abnormal hair follicles, sweat glands and teeth and makes one unable to regulate temperature: overheat easily
What are the main cells of the epidermis?
- keratinocytes
- melanocytes,
Langerhans cells,
Merkel cells
What are the main cells of the dermis?
- fibroblasts, collagen, elastic
- blood vessels, nerve endings
What are the main cells of the subcutis?
- fat
- blood vessels, fibrous septae
How does the epidermis re-new itself?
Cells grow from stem cells in the basal layer and are shed from the surface and “sheds” itself on average every 28+ days
- 14 days to reach stratum corneum
- 14 days to desquamate
NOTE: cells terminally differentiate as they move upwards
What are the four layers of the epidermis?
What is the function of the basal layer of the epidermis?
It is the source of stem cells
Basal cells adhere to dermis (basement membrane zone) through ___________.
hemidesmosomes
Types of cell junctions in the skin
- desmosomes: KC-KC adhesion
- hemidesmosomes: epidermis-dermis adhesion
- adherens junctions: links actin filaments KC-KC
- gap junctions: connexin proteins, important in cell-cell communication `
What happens in the spinous layer of the skin?
- Cells stop dividing and start terminal differentiation
- Develop lipids (lamellar granules) important in barrier function
What is being shown here (in the spinous layer of the epidermis)?
“spiny” due to visible desmosomes with which one KC adheres to another
What layer of the epidermis is this?
Granular cell layer
What happens in the granular layer of the epidermis?
- Intracellular keratohyaline granules synthesized (including profilaggrin)
- Lipids in lamellar granules secreted into intercellular space to form water barrier to keep water in skin
What happens in the stratum corneum layer of the epidermis?
- Nuclei and organelles degenerate, cells flatten
- Profilaggrin processed into filaggrin, which help keep water in cells
- Keratins (structural cytoskeletal proteins) combine with filaggrin into macrofibrils that create protective layer
What is keratin?
The major fibrous structural proteins in hair and nails that combine to form intermediate filaments
Mechanically stabilize cell against physical stress
Have large amounts of sulfur-containing amino acid cysteine (esp hair and nails)
Stratum corneum from different sites
Left: trunk
Right: palm
What cell is this?
melanocyte (“live” along basal cells with about one per 10 keratinocytes)
produce pigment and live in the basal layer but processes extend into the stratum spinosum
Where do melanocytes come from?
Derived from neural crest and migrate during embryonic development
What cell is this? Function?
Langerhans cell- antigen presenting
What are Merkel cells?
They are associated with the sense of light touch discrimination of shapes and textures. They can turn malignant and form the skin tumor known as Merkel cell carcinoma.
The main function of the dermis is support. How does it accomplish this?
The primary cell in dermis is fibroblast (mesenchymal origin) and these fibroblasts are responsible for synthesis and degradation of connective tissue proteins, including collagen, elastin, glycosminoglycans and other glycoproteins
- Injury to skin triggers fibroblast mitosis
- Responsible for wound healing and scar formation
What are these?
Specialized tissue cells in the dermis rich in histamine and heparin granules that can release their granules when triggered by injury or when they bind IgE antibodies during allergic reactions
•Cause characteristic “wheal and flare”
What are eccrine sweat glands?
“true” sweat glands
- Present throughout the body
- Open directly onto the skin (not associated with hair follicle)
- Function to regulate temperature by evaporative cooling of sweat
Describe the subcutis and its functions
This is the fat layer that separates the dermis from underlying structures including fascia, muscle, organs
It provides:
- insulation
- a source of energy
- protection from injury
How does sunburn affect the epidermis?
Damaged keratinocytes
- “sunburn cells”
Failure to “delete” damaged cells can result in skin cancer
