Vessels, Nerves, and Psychodermatology

Question 1

Where is the itch sensation limited to?

Answer 1

Skin, mucosa, and cornea

Question 2

Describe Merkel cells

Answer 2

Light touch
Slow-adapting Aβ sensory fiber
Located along the stratum basale between keratinocytes

Question 3

Answer 3

Meissner’s corpuscle

Question 4

Describe Messiner’s corpuscle

Answer 4

Touch (dynamic skin deformation)
Rapidly-adapting Aβ sensory fiber

Question 5

Answer 5

Merklel cell

Question 6

Describe Ruffini corpuscle

Answer 6

Stretch
Slow-adapting Aβ sensory fiber

Question 7

Answer 7

Pacinian corpuscle

Question 8

Answer 8

Pacinian corpuscle

Question 9

Describe Pacinian corpuscles

Answer 9

High pressure, vibration
Rapidly-adapting Aβ sensory fiber

Question 10

Describe the sensation of hair follicles

Answer 10

Light touch, low-requency vibration
All types of sensory fibers

Question 11

What are the three intercommunicating plexuses of arteries and veins?

Answer 11

1) Deep plexus (interface of dermis and subcutis - some branches supply lower hair follicle and epitrichial sweat glands)
2) Middle plexus (level of the sebaceous gland and supplies arrector pili, middle hair follicle, and sebaceous glands)
3) Superficial plexus (capillary loops just below the epidermis - supplies upper hair follicle and epidermis)

Question 12

Describe arterioles

Answer 12

endothelial cells surrounded by smooth muscle cells, most likely function as part of the resistance vessels in skin

Question 13

How do capillaries differ from arterioles?

Answer 13

Smaller and lack surrounding smooth muscle cells

Question 14

Describe venules

Answer 14

A majority of dermal vessels are post-capillary venules
Most physiologically reactive segment of the microcirculation, are where inflammatory cells migrate from the vasculature to the tissue and where endothelial cells develop gaps due to inflammation which increases vascular permeability

Question 15

What are the three sections of the microcirculatory bed?

Answer 15

Arterioles, capillaries, and venules

Question 16

What IHC stain is useful for diagnosis of vascular neoplasms and for identification of vascular invasion by neoplasms?

Answer 16

Factor VIII-related antigen

Question 17

What happens to selectins and members of the immunoglobulin superfamily on endothelial cells with inflammation?

Answer 17

E- and P-selectin as well as ICAM-1/VCAM-1 are upregulated and mediate rolling, adhesion, and transmigration of leukocytes (ex. neutrophils) from the blood

Question 18

What are the 3 main functions of the endothelium?

Answer 18

1) maintain homeostasis of the blood
2) separate blood from tissues
3) regulate blood flow

Question 19

Name 3 signaling molecules that regulate dermal angiogenesis.

Answer 19

1) Mast cells (histamine)
2) Macrophages (TNF-α)
3) TGF-β

Question 20

Describe pericytes

Answer 20

• Aligned parallel to the blood vessels and vary in appearance from club-like to fusiform
• Contractile cells that contain actin-like and myosin-like filaments and regulate capillary flow
• Unknown origin
• Integral part of vessel wall and enmeshed in mural basement membrane material

Question 21

Describe veil cells

Answer 21

• Flat, advential, fibroblast-like cells that surround all dermal microvessels
• exact function and nature are undetermined
• entirely external to vessel wall and demarcates it from the surrounding dermis
• perivascular mast cells are usually present in the space between the walls and the veil cells

Question 22

What IHC stain would you use to identify veil cells?

Answer 22

Factor XIIIa (indicates that it is part of the dermal dendrocyte system)

Question 23

Describe arteriovenous anastomoses

Answer 23

Normal connections between arteries and veins that allow arterial blood to enter the veins and bypass the capillaries
- associated with thermoregulation (ex. waterbird feet)
- occur in all areas but more common in extremities
- occur at all layers of the dermis but especially the deep dermis
- vary in structure from simple to the glomus
- can be pathologic

Question 24

What causes dilation of arteriovenous anastomoses?

Answer 24

Acetylcholine and histamine

Question 25

What causes constriction of arteriovenous anastomoses?

Answer 25

Epinephrine and norepinephrine

Question 26

What is a glomus?

Answer 26

• A special AV shunt located in the deep dermis
• Consists of an arterial section (Sucquet-Hoyer canal) which branches from an arteriole and a venous section that is thin-walled with a wide lumen
• Has a tunica media that is densley packed with 4-6 layers of golmus cells that are large and pump, have clear cytoplasm, and resemble epithelial cells
• the glomus cells are generally regard as modified smooth muscle cells

Question 27

Describe pathologic AV anastomoses/fistulae

Answer 27

• Can be congenital or acquired through trauma
• Hard to treat, surgery is frequently recommended
• Frequently in legs/limbs
• Arteriography can visualize them

Question 28

Where do the cutaneous lymphatics arise from?

Answer 28

Capillary networks in the superficial dermis (though not usually seen in routine histopath preparations above the mid-dermis)

Question 29

What are the functions of the dermal lymphatics?

Answer 29

• Control movement of interstitial tissue fluid so are essential for nutrition and control the true microcirculation of the skin
• Drain and take away material that arises through daily wear and tear so are important for the recycling of protein and cellular debris as well as removing topical medications/toxins, injected medications, etc
• Link skin to lymph nodes for immune regulation

Question 30

Describe lymph formation and the removal via contractions

Answer 30

• Initial collector system is non-contractile, have an attenuated endothelial layer, discontinuous BMZ, and non-continuous cell junctions
• Lymph formation depends on periodic expansion of the lymphatics and compression (caused muscle contractions and physical motion) which causes emptying of the initial lymphatics to contractile lymphatics that have smooth muscle and exhibit peristalsis

Question 31

How do you distinguish lymphatics from capillaries on H&E?

Answer 31

• Lymphatics have a wider/more angular lumen, more attenuated and flattened endothelial cells, no pericytes, shouldn’t have blood (but might with injury or inflammation)

Question 32

What are Voight lines?

Answer 32

Boundaries of areas of distribution of the main cutaneous nerve stems

Question 33

What are Langers lines?

Answer 33

Reflect the course of blood vessels or lymphatics

Question 34

What are Blaschko’s lines?

Answer 34

• Lines follow a V-shape over the spine, S-shape on the abdomen, axial distribution on limbs, wavy on the face
• Reflect a mosaic condition

Question 35

What are cleavage lines?

Answer 35

Same as tension lines