Intro to biology of the skin Flashcards
What is the epidermis comprised of?
primarily keratinocytes melanocytes, Langerhans cells, Merkel cells
What is the dermis comprised of?
Fibroblasts, collagen, elastic (fibers?), blood vessels, nerve endings
What is the subcutis comprised of?
Fat, blood vessels, fibrous septae
Function of epidermis?
barrier function, protection, wound healing
Function of dermis?
structural support, vascular support and innervation
How does the epidermis replace itself?
Every 28+ days: 1. cells grow from stem cells in the basal layer 2. terminally differentiate as they move upwards 3. shed from the surface
4 layers of epidermis? (top to bottom)
- stratum corneum
- stratum granulosum
- stratum spinosum
- stratum basale
What is produced in the basal layer?
stem cells
How do basal cells adhere to dermis?
hemidesmosomes
What occurs in the spinous layer?
cells stop dividing and commence terminal differentation
What are produced in the spinous layer?
lipids (lamellar granules) which are important in barrier function
What makes the spinous layer “spiny”?
visible desmosomes with which one KC adheres to another
How do keratinocytes adhere to one another?
desmosomes in the spinous layer
What is synthesized in the granular cell layer?
Intracellular keratohyaline granules containing profilagrin
Desmosomes are located in the _____ layer.
Hemidesmosomes are located in the _____ layer.
Spinous
Basal
What forms the water barrier within the granular layer to keep water in skin?
Lipids in lamellar granules (formed in spinous layer) secreted into intercellular space
Where is profilaggrin synthesized? Where is it processed?
- granular layer
- stratum corneum (into flaggrin)
What makes the stratum corneum protective?
- keratinocytes (keratin + flaggrin combined to form microfibrils)
- lipid mixture surrounding keratinocytes, which provide water barrier
What is the stratum corneum comprised of?
- flattened cells with degenerated nuclei/organelles
- flattened keratinocytes(filled with keratin and flaggrin)
- lipid mixture surrounding keratinocytes
Over 40+ different keratins combine to form…
intermediate filaments, whose pairs differ by location
Keratin is comprised of large amounts of what amino acid?
cysteine (especially hair/nails)
What is the function of keratin?
Mechanically stabilize cell against physical stress
What’s this?
melanocyte
What is the function of melanocytes?
trasfer pigment (malanin) to keratinocytes via dendritic processes
What is the embryonic origin of melanocytes?
neural crest, migrated during development
Where are melanocytes located?
along the basal layer, surrounded by keratinocytes
melanocyte
What are Langerhans cells?
Dendritic cells in mid-epidermis with immunologic function
What is the function of Langerhans cells?
Recognize abnormal antigens in skin; take them up, process, and present to lymphocytes in regional lymph nodes
Langerhans cells are important in: (2)
- allergic reactions
- tumor surveillance
Langerhans cell
Where are Merkel cells located? What is their function?
mechanoreceptor cells located in the basal layer
Dermis functions primarily in:
support
Dermis contains:
- blood vessels
- lymphatics
- Nerves
- Sweat/oil glands
- Hair follicles
Important CT proteins in the dermis
collagen, elastin, glycosminoglycans
Injury to skin triggers:
mitosis of fibroblasts in dermis, which are responsible for wound healing and scar formation
Important cells in dermis:
mast
fibroblast (MOST important)
Hair follicles extend:
through dermis into the subcutis
The pilosebaceous unit consists of:
- Hair follicle
- Associated sebaceous (oil) gland
- Apocrine sweat glands (in axilla and anogenital skin)
- Arrector pili muscle
What are the “true” sweat glands, and what is their function?
eccrine sweat glands, which are not associated with a hair follicle
Open directly onto the skin, and function to regulate temperature by evaporative cooling of sweat
Subcutis serves as:
- insulation
- a source of energy
- protection from injury
What is the subcutis?
Fat layer that separates dermis from underlying structures including fascia, muscle, organs
What happens to “sunburn cells”?
Damaged keratinocytes (“sunburn cells”) apoptose, which is the normal response to damage
Failure to “delete” damaged cells can result in what?
skin cancer
Pemphigus vulgaris results from dysfunction of the ____ layer
spinous
Bullous Pemphigoid results from dysfunction of the ____ layer
basal layer of the epidermis
Genetic defects in filaggrin is associated with:
Atopic dermatitis
What causes blister formation in Epidermolysis Bullosa?
genetic mutations in keratin 5/14 results in keratinocytes which break apart
benign collection of melanocytes
Nevus (mole)
What tissue layer functions as a permeability barrier?
epidermis
Which tissue layers protect against pathogens?
epidermis
dermis
Which tissue layers function in thermoregulation?
epidermis
dermis
subcutis
Which tissue layer functions in UV protection?
epidermis
Which tissue layers function in sensation?
epidermis
dermis
subcutis
Which tissue layers function in wound repair and regeneration?
epidermis
dermis
Which tissue layers function in physical appearance?
epidermis
dermis
subcutis
