Intro to Skin

Question 1

What are the main skin cells invovled in immune regulation?

Answer 1

Langerhans cells in epidermis, lymphocytes and dermal dendritic cells in dermis

Question 2

What are the main cells involved in damage repair of the skin? Thermo-reg? Photoprotection?

Answer 2

keratinocyte proliferate in epidemis in response to injury or inflammation, fibroblasts in dermis

Theromreg: vasculature in dermis

Photoprotection: melanocytes

Question 3

What is this?

Answer 3

Atophic dermatitis

Question 4

Why is intact skin a poor host for infection?

Answer 4

Skin sheds, the epidermis does not have vessels, and is dry

Question 5

Skin response to acute sunburn

Question 6

What is Hypohidrotic ectodermal dysplasia?

Answer 6

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

Question 7

Answer 7

Question 8

What are the main cells of the epidermis?

Answer 8

• keratinocytes
• melanocytes,

Langerhans cells,

Merkel cells

Question 9

What are the main cells of the dermis?

Answer 9

• fibroblasts, collagen, elastic
• blood vessels, nerve endings

Question 10

What are the main cells of the subcutis?

Answer 10

• fat
• blood vessels, fibrous septae

Question 11

How does the epidermis re-new itself?

Answer 11

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

Question 12

What are the four layers of the epidermis?

Answer 12

Question 13

What is the function of the basal layer of the epidermis?

Answer 13

It is the source of stem cells

Question 14

Basal cells adhere to dermis (basement membrane zone) through ___________.

Answer 14

hemidesmosomes

Question 15

Types of cell junctions in the skin

Answer 15

• desmosomes: KC-KC adhesion
• hemidesmosomes: epidermis-dermis adhesion
• adherens junctions: links actin filaments KC-KC
• gap junctions: connexin proteins, important in cell-cell communication `

Question 16

What happens in the spinous layer of the skin?

Answer 16

• Cells stop dividing and start terminal differentiation
• Develop lipids (lamellar granules) important in barrier function

Question 17

What is being shown here (in the spinous layer of the epidermis)?

Answer 17

“spiny” due to visible desmosomes with which one KC adheres to another

Question 18

What layer of the epidermis is this?

Answer 18

Granular cell layer

Question 19

What happens in the granular layer of the epidermis?

Answer 19

• Intracellular keratohyaline granules synthesized (including profilaggrin)
• Lipids in lamellar granules secreted into intercellular space to form water barrier to keep water in skin

Question 20

What happens in the stratum corneum layer of the epidermis?

Answer 20

• 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

Question 21

What is keratin?

Answer 21

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)

Question 22

Stratum corneum from different sites

Left: trunk

Right: palm

Question 23

What cell is this?

Answer 23

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

Question 24

Where do melanocytes come from?

Answer 24

Derived from neural crest and migrate during embryonic development

Question 25

Answer 25

Question 26

What cell is this? Function?

Answer 26

Langerhans cell- antigen presenting

Question 27

What are Merkel cells?

Answer 27

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.

Question 28

The main function of the dermis is support. How does it accomplish this?

Answer 28

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

Question 29

What are these?

Answer 29

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”

Question 30

What are eccrine sweat glands?

Answer 30

“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

Question 31

Describe the subcutis and its functions

Answer 31

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

Question 32

How does sunburn affect the epidermis?

Answer 32

Damaged keratinocytes

• “sunburn cells”

Failure to “delete” damaged cells can result in skin cancer

Question 33