Skin Flashcards
How many layers are in the epidermis?
Thick skin: 5 epidermal
thin skin: 4 epidermal layers
Stratum basale is also known as
Stratum germinativum
Stratum germinativum (stratum basale) contains which cells?
- melanocytes
- Keratinocytes
- Stem cells (5-10% of layer)
What is synthesized in the stratum basale/Stratum germinativum?
K5 and k14 isoforms of keratin
Characteristics of stratum basale/Stratum germinativum
- deepest layer
- cube to column-shaped keratinocytes
Characteristics of the stratum spinosum
- Second deepest layer
- Thickest layer
- Several rows of cube-shaped keratinocytes (post-mitotic)
(keratinocytes in the stratum basale are mitotically active)
What is synthesized in the stratum spinosum layer of the epidermis?
- K1 and K10 isoforms of keratin (called cytokeratin: keratin made by keratinocytes)
- Membrane - coating granule that will release lipid contents secreted onto the surface of the skin
Tonofilaments
- Intermediate filaments used to connect the cells in the stratum spinosum
- Made up of the Keratin isoforms made in the stratum spinosum
Stratum spinosum is named due to
Spiny appearance of the keratinocytes during tissue preparation
Describe the stratum granulosum
- 1 thin skin to 5 thick skin rows of flattened keratinocytes
- most superficial layer in which cells retain their nuclei
Keratohyalin granules
deeply basophilic irregular granules located in stratum granulosum
filaggrin precursor
- keratohyalin granule precursor
- histadine-rich protein
- leads to flattened shape of cells (complexes w/keratin forming a cement-like aggregate)
Secretion of membrane-coating granules in the stratum granulosum are used to
- provide the waterproofing barrier along with involucrin
- Triggers apoptosis of keratinocytes
stratum lucidum
- ONLY IN THICK SKIN
- Flat cells with a light, translucent appearance
- Packed with keratin filaments with degenerated nuclei and organelles
Stratum corneum
- Multiple layers of very flat, fully keratinized cells
- All the cells are dead in this layer and packed with keratin, surrounded by involucrin, other proteins, and a phospholipid coat
- This is all utilized to help shield the underlying soft tissues
- Sloughed off dead cells at the most superficial layer are called “squames”
What is the major cell type in the epidermis?
Keratinocytes
Function of keratinocytes
- Keratin synthesis
- Formation of water barrier
Location of melanocytes
Stratum basale
(also seen in hair follicles and dermis)
Characteristics of melanocytes
- Round cell bodies with long cytoplasmic extensions between the stratum spinosum
- Clear cell body compared to keratinocytes
