L12- Skin renewal and aging

Question 1

What is the structure of the skin?

Answer 1

Epidermis
Dermis
Hypodermis

Question 2

What is the function of the skin?

Answer 2

1. Protection (from radiation, dehydration, microoorganisms, trauma)
2. Regulation (of body temperature, circulation, excretion)
3. Sensation (pressure, heat, pain)

Question 3

What are the layers of the epidermis (top to bottom)?

Answer 3

• S corneum- protection via corneocytes
• S. granulosum- waterproof barrier (keratin granules)
• S. spinosum- immunity, endocrine
• S. basale- UV protection, sensation, homeostasis (nerve endings)

Question 4

What does the dermis do?

Answer 4

• Immunity
• Sensation
• Movement and growth

Question 5

How does epidermal homeostasis occur?

Answer 5

• Ongoing renewal through tissue turnover or following injury
• Different resident stem cell pools contribute to the maintenance/repair of different epidermal tissues of the skin

Question 6

How is circadian rhythm involved in epidermal regeneration?

Answer 6

• Differentiation in the morning
• DNA damage by UV rays in the day
• Proliferation in the evening

Question 7

What are the major ECM components of the dermis?

Answer 7

• Collagen
• Elastin
• Proteoglycans
• Glycosaminoglycans

Question 8

What is collagen?

Answer 8

• Main structural body for the skin
• In relaxed state fibres arrange randomly and in stretching they align parallel to eachother
• Collagen has high tensile strength and is stiff and lacks extensibility
• Structural support but no recoiling abilities

Question 9

What is elastin?

Answer 9

• Long range extensibility, even after maximal strain it returns to its original shape
• Promotes return of collagen to its wavy posture at rest
• Recoils skin after stretch

Question 10

What is glycosaminoglycan?

Answer 10

Name used for six different types of long linear polysaccharide chains

Question 11

What is hyaluronic acid?

Answer 11

Simplest GAG
Forms large complexes of HA and HA binding proteoglycan aggregates
Crosslinking to collagent networks increases tissue stiffness

Question 12

What are basement membranes made up of?

Answer 12

Condensed networks of ECM proteins
• Laminins
• Collagen IV
• Collagen VII
• Nidogens and perlecan

Question 13

What is the main mechanism of skin aging?

Answer 13

• Loss of mature collagen and increase matrix metalloproteinase expression (increases collagen fragmentation and degradation)
• Impaired TGF-b signalling causes reduction of collagen synthesis