Skin

Question 1

How many layers are in the epidermis?

Answer 1

Thick skin: 5 epidermal

thin skin: 4 epidermal layers

Question 2

Stratum basale is also known as

Answer 2

Stratum germinativum

Question 3

Stratum germinativum (stratum basale) contains which cells?

Answer 3

1. melanocytes
2. Keratinocytes
3. Stem cells (5-10% of layer)

Question 4

What is synthesized in the stratum basale/Stratum germinativum?

Answer 4

K5 and k14 isoforms of keratin

Question 5

Characteristics of stratum basale/Stratum germinativum

Answer 5

• deepest layer
• cube to column-shaped keratinocytes

Question 6

Characteristics of the stratum spinosum

Answer 6

1. Second deepest layer
2. Thickest layer
3. Several rows of cube-shaped keratinocytes (post-mitotic)

(keratinocytes in the stratum basale are mitotically active)

Question 7

What is synthesized in the stratum spinosum layer of the epidermis?

Answer 7

1. K1 and K10 isoforms of keratin (called cytokeratin: keratin made by keratinocytes)
2. Membrane - coating granule that will release lipid contents secreted onto the surface of the skin

Question 8

Tonofilaments

Answer 8

1. Intermediate filaments used to connect the cells in the stratum spinosum
2. Made up of the Keratin isoforms made in the stratum spinosum

Question 9

Stratum spinosum is named due to

Answer 9

Spiny appearance of the keratinocytes during tissue preparation

Question 10

Describe the stratum granulosum

Answer 10

• 1 thin skin to 5 thick skin rows of flattened keratinocytes
• most superficial layer in which cells retain their nuclei

Question 11

Keratohyalin granules

Answer 11

deeply basophilic irregular granules located in stratum granulosum

Question 12

filaggrin precursor

Answer 12

• keratohyalin granule precursor
• histadine-rich protein
• leads to flattened shape of cells (complexes w/keratin forming a cement-like aggregate)

Question 13

Secretion of membrane-coating granules in the stratum granulosum are used to

Answer 13

• provide the waterproofing barrier along with involucrin
• Triggers apoptosis of keratinocytes

Question 14

stratum lucidum

Answer 14

• ONLY IN THICK SKIN
• Flat cells with a light, translucent appearance
• Packed with keratin filaments with degenerated nuclei and organelles

Question 15

Stratum corneum

Answer 15

• 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”

Question 16

What is the major cell type in the epidermis?

Answer 16

Keratinocytes

Question 17

Function of keratinocytes

Answer 17

• Keratin synthesis
• Formation of water barrier

Question 18

Location of melanocytes

Answer 18

Stratum basale

(also seen in hair follicles and dermis)

Question 19

Characteristics of melanocytes

Answer 19

• Round cell bodies with long cytoplasmic extensions between the stratum spinosum
• Clear cell body compared to keratinocytes