Dermis Structure

Question 1

Basic structure of the skin

Answer 1

-epidermis (superficial) adhered to dermis just below by the dermoepidermal junction

Question 2

Dermal matrix composition

Answer 2

• collagen fibers + elastin fibers + ground substance

- synthesized by fibroblasts w/in dermis

Question 3

Characteristics and purpose of dermoepidermal jucntion

Answer 3

• epidermal rete=downward projections of epidermis
• dermal papillae=upward projections of dermis
• interlocking pattern increases adherence strength and surface area (btwn epidermis and dermis) –> passage of nutrients
• pattern on hands and feet –> epidermal ridges (“fingerprints”)

Question 4

General characteristics and typesof collagen

Answer 4

• “building block” of dermis
• provides tensile strength of skin
• three proteins arranged in alpha-helical structure
• repeated strings of Gly-X-Y (usually Gly-Pro-hydroxyproline)
• Main types: Collagen I, III, IV, VII

Question 5

Type I Collagen characteristics

Answer 5

• > 85% of adult dermis

- major component of bone

Question 6

Type III Collagen characteristics

Answer 6

• fetal dermis component

- reason why fetal skin forms less scars

Question 7

Type IV Collagen characteristics

Answer 7

• high concentrations found in basement membrane zone (i.e. @ dermoepidermal jxn)
• prominent around vessels

Question 8

Type VII Collagen characteristics

Answer 8

• found anchoring fibrils

- used to to attach epidermis to dermis

Question 9

Sites of collagen synthesis and assembly

Answer 9

• synthesis=intracellular (fibroblasts)

- assemnly=extracellularly (w/cofactors –> vit C)

Question 10

Ehlers-Danlos syndrome (EDS) characteristics

Answer 10

• disordered collagen production due to genetic defects
• skin hyperextensibility, joint hyperextensibility
• tissue fragility
• poor wound healing

Question 11

Elastic fiber characteristics

Answer 11

• provide skin resiliency=ability to be distorted and return to orignal shape
• normally argyrophillic=”silver-loving” –> visible w/silver-based stains
• sun-damaged elastic fiber (e.g. in solar elastosis) =basophillic

Question 12

Pseudoxanthoma elasticum (PXE) characteristics

Answer 12

• mutation in gene encoding multidrug resistance complex
• elastic fibers–>enlarged, tangled, and calcified
• histologically blue-purple
• “plucked-chicken” skin

Question 13

Ground substance components

Answer 13

• gelatinous material between and amongst collagen bundles, elastic fibers, other structures of dermis
• glycosaminoglycans: hyaluronic acid and dermatan sulphate (can absorb water)
• fibronectins=”glue”
• helps facilitate nourishment of epidermis
• constantly being destroyed and renewed

Question 14

Functions of cutaneous vascular system

Answer 14

• wound healing
• control of homeostasis: via Sucquet-Hoyer canal (smooth muscle valve) blood directed towards or away from skin
• modulation of inflammation/leukocyte trafficking: express intracellular adhesion molecules (ICAMs) that allow adherence and rolling of WBCs

Question 15

Leukocytoclastic vasculitis characteristics

Answer 15

• immune complex formation within post-capillary venules in dermis
• often post-Strep infection
• palpable purpura

Question 16

Important nervous tissue structures in dermis

Answer 16

• meissner’s corpuscles
• free nerve endings
• pacinian corpuscle