Structure & Function Of The Skin - Dermis

Question 1

Where do hair follicles & sweat glands originate

Answer 1

Subcutaneous fat, below dermis

Question 2

Where does the epidermis get its blood & lymph supply

Answer 2

The dermis

Question 3

What is the dermo-epidermal junction

Answer 3

Interface between epidermis and dermis where the epidermal basal cells bind to the connective tissue basement membrane via hemidesmosomes

Question 4

What is the function of the dermo-epidermal junction

Answer 4

• Support, adhesion, growth and differentiation of basal cells
• Semi-permeable membrane acting as barrier and filter

Question 5

How are epidermal basal cell keratinocytes anchored to the basement membrane vs each other

Answer 5

To basement membrane - Hemidesmosomes
To each other - Desmosomes

Question 6

Describe the structure of the dermis, including the cellular components

Answer 6

• Mainly composed of ground substance of connective tissue
• Fibroblasts
• Macrophages, mast cells, lymphocytes, langerhans cells
• Fibres - collagen (main) & some elastin
• blood vessels, lymphatics, nerves, muscles

Question 7

How is the dermis different in different skin types

Answer 7

Black/ Asian skin type
- thicker dermis
- smaller, more closely stacked collagen fibres
- more macrophages & fibroblasts

Question 8

What happens to the dermis during photoaging

Answer 8

• Collagen loss: Photoaging causes a loss of collagen, which is a structural protein in the dermis. This makes skin weaker and more likely to wrinkle.
• Elastin damage: Photoaging causes a buildup of disorganised elastin fibers in the deep dermis, and a loss of small elastin fibers in the upper dermis.
• DNA changes: UV light damages the DNA in skin cells, which can lead to skin cancer.

Question 9

Describe the blood supply in the dermis & subcutaneous tissue

Answer 9

Horizontal plexuses within the dermis
AV anastomoses (shunts) in subcutaneous tissue to enable bypass of superficial capillaries when cold

Question 10

Describe the lymphatic supply of the dermis

Answer 10

Superficial, smaller, non contractile vessels (drain to…)
Deep, larger, contractile lymphatic trunks

Question 11

Describe the function of lymphatic vessels in the dermis

Answer 11

• allow passage of Langerhans cells to lymph nodes
• channelling of micro-organisms / toxins

Question 12

Describe the nerves within the dermis

Answer 12

Free nerve endings
- non-capsulated nerve endings
- serve a general sensory function
- can serve a specialised function e.g. itch or pain

Meissner’s corpuscles
- encapsulated nerve endings
- highly sensitive to light touch & detect vibrations

Pacinian corpuscles
- encapsulated nerve endings
- detect pressure

Question 13

What is the role of the fibroblasts in the dermis

Answer 13

Maintain ground substance, produce collagen

Question 14

What is the role of macrophages in the dermis

Answer 14

Part of the skin’s innate immune system
- Phagocytosis
- Antigen presentation
- Cytokine release
- Can form granulomas