5. Skin Histology Flashcards
1
Q
- Identify and describe the characteristic histological and cytological features of cells from skin (objective)
A
Answer later
2
Q
- Describe the physiological roles of different cell types from the skin (objective)
A
Answer later
3
Q
Protective Function of Skin
A
- Physical barrier against thermal and mechanical insults and most potential pathogens
- Dark pigment melanin in epidermis protects cell nuclei from UV radiation
- Permeability barrier against excessive loss or uptake of water
- Selective permeability of some lipophillic drugs
4
Q
Sensory Function of Skin
A
- Sensory receptors allow skin to constantly monitor the environment
- Various skin mechanoreceptors help regular body’s interactions with physical objects
5
Q
Thermoregulatory Function of Skin
A
- Constant body temperature is normally easily maintained thanks to skin’s insulating components (ie fatty layer and hair on the head)
- Mechanisms for accelerating heat loss (sweat production and a dense superficial microvasculature), especially with fatty tissue
6
Q
Metabolic Function of Skin
A
- Cells of skin synthesize vitamin D3, needed in calcium metabolism and proper bone formation, through local action of UV light on the vitamin’s precursor
- Excess electrolytes can be removed in sweat, and the subcutaneous layer stores a significant amount of energy in the form of fat
7
Q
Other General Properties of Skin
A
- Elasticity
- Self-renewing throughout life (injured skin is repaired rapidly)
8
Q
General Layers of Skin
A
Epidermis, Dermis (papillary and reticular layer), Subcutaneous Layer
9
Q
Epidermis (general)
A
- Forms major distinction between thick skin (palms and soles, 400-1400um) and thin skin (75-150um)
- Lacks microvasculature but receives nutrients and oxygen by diffusion from dermis
10
Q
Epidermis is a stratified squamous keratinized epithelium
A
Cellular component:
-epithelial cells are called keratinocytes (squamous cells)
-pigment producing melanocytes
-antigen-presenting Langerhans cells
-Tactile Merkel cells
Layers:
-stratum basale, spinosum, granulosum, lucidum, corneum
11
Q
Stratum Basale
A
- Intense mitotic activity and contains (along with deepest part of next layer) all progenitor cells for all epidermal layers
- Single layer of basophilic cuboidal or columnar cells on the basement membrane at dermal-epidermal junction
- Hemidesmosomes in basal cell membranes join these cells to the basal lamina
- Desmosomes bind cells together in their lateral and upper surfaces
- During differentiation cells move upward
12
Q
Stratum Spinosum
A
- Just above basal layer
- Thickest layer, especially in epidermal ridges
- Consists of generally polyhedral cells with central nuclei
- Desmosomes holding cell layers together
- Thick skin subject to continuous friction and pressure (such as foot soles) has a thicker stratum spinosum
- Most basal layer can repair
13
Q
Stratum Granulosum
A
- 3-5 layers of flattened cells, undergoing terminal differentiation process of keratinization
- Cytoplasm is filled with intensely basophilic masses (called keratohyaline granules and lamellar granules)
- Lamellar granules undergo exocytosis, producing lipid-rich impermeable layer around the cells
14
Q
Stratum Lucidum
A
- Only in thick skin
- Consists of a thin, translucent layer of flattened eosinophilic keratinocytes held together by desmosomes
- Nuclei and organelles have been lost
- Cytoplasm consists almost exclusively of packed keratin filaments
15
Q
Stratum Corneum
A
- 15-20 layers of squamous, keratinized cells
- By end of keratinization, the cells only contain amorphous fibrillar proteins with plasma membranes surrounded by lipid-rich layer
- These fully keratinized or cornified cells called squames are continuously shed at epidermal surface as desmosomes and lipid-rich envelopes break down
