Biology of Skin and Wound Healing

Question 1

Layers of the Epidermis

Answer 1

1. Stratum Corneum
2. Stratum Lucidium (only in thick skin)
3. Stratum Granulosum
4. Stratum Spinosum
5. Stratum Basale

Question 2

Keratinocytes

Answer 2

Most abundant cell in the epidermis
Stem cells reside in the stratum basale
Produce keratin filaments that disulfide bond together
Migrate apically and die at the surface

Question 3

Melanocytes

Answer 3

Responsible for production of melanin
All humans have the same # of melanocytes
Lack desmosomes
Tyrosinase and oxidation of tyrosine cause pigmentation
Derived from neural crest cells

Question 4

Langherhan Cells

Answer 4

Immune cell responsible for trapping antigens and initiating immune response
Found in stratum spinosum
Derived from bone marrow

Question 5

Merkel Cells

Answer 5

Found in the stratum basale
Tactile and mechanorececptor cells
Differentiate from epithelial cells

Question 6

Stratum Basale

Answer 6

Home of the epidermal stem cell

Daughter cells differentiate and migrate apicaly

Question 7

How do keratinocytes obtain melanine?

Answer 7

Cytocrine Secretion by melanocytes

Question 8

Stratum Spinosum

Answer 8

Keratinocytes containing increased number of tonofilaments

Numerous desmosomes

Question 9

Stratum Granulosum

Answer 9

Basophilic Keratohyalin granules
Composed of Filaggrin and Trichohyalin
Region of vitamin D synthesis

Question 10

Stratum Lucidum

Answer 10

Present only in thick skin

Cells lack nuclei and typical organelles

Question 11

Stratum Corneum

Answer 11

Outermost layer of epidermis
Composed of dead keratinocytes
Cells attached via desmosomes

Question 12

Epidermis Junction to Dermis

Answer 12

Rete Ridges of epidermis attach to Papillary ridges of the dermis via hemidesmosomes

Question 13

Papillary Layer

Answer 13

Loose CT
Contains capillaries and nerves
Encapsulated nerve endings Meissner Corpuslces

Question 14

Reticular Layer

Answer 14

Made up of dense-irregular CT
Thick bundles of collagne
Large blood vessels
Nerves and encapsulated nerve endings - Paccininan corpuscles

Question 15

What is found only in thin skin

Answer 15

Sebaceous Glands and Hair Follicles

Question 16

What is found both in thin and thick skin

Answer 16

Sweat Glands

Question 17

Stages of Wound Healing

Answer 17

1. Hemostasis
2. Inflamation
3. Proliferation
4. Remodeling

Question 18

Hemostasis Phase of WH

Answer 18

Platelets cause clotting and stop bleeding
Clot contains fibrin, fibronectin and collagen
Clot acts as a reservoir to help trap growth factors

Question 19

Inflammatory Phase of WH

Answer 19

Early
Platelets release PDGF and TGF B to attract PMN
PMN releaes colagenase and elastase
PMNs eat bacteria and foreign stuff
PMNs are replaced by macrophages :)
Late
Macrophages eat everything including PMNs
Mphages release cytokines
Cytokines recruit fibroblasts

Question 20

Proliferative Phase of WH

Answer 20

3-4 days after injury
Fibroblasts secrete new collagen, elastin and proteoglycans
secrete VEGF

Question 21

Remodeling Phase of WH

Answer 21

TGF-B converts fibroblasts to myofibrobasts leads to wound contraction
Replace type III colagen with type I
Tissue is about 80% as strong as normal tissue