Lecture 2 - derm

Question 1

What does the dermis contain?

Answer 1

• It’s got the goods!

blood vessels, nerves, and cutaneous appendages (hairs, sweat glands/ducts, etc.)

• needs a way to share it

Question 2

Where is the dermis located?

Answer 2

Beneath the epidermis and above the subcutaneous tissue

Question 3

How is the vascular supply of the dermis broken up?

Answer 3

○ Vascular supply is broken into 2 plexus:

• Superficial horizontal plexus
• Deep horizontal plexus

Question 4

adnexal (appendageal) structures: examples

Answer 4

– hair follicles 
– eccrine glands 
– apocrine glands 
– apoeccrine glands 
– sebaceous glands 
– n/v

Question 5

Which one has thin collagen bundles: papillary dermis of reticular dermis?

Answer 5

papillary dermis

reticular has thick collagen bundles with visible elastic fibers

Question 6

• Building blocks of the dermis:

Answer 6

1) Collagen – forms the tensile strength
2) Elastic fibers – allow for resilience
3) Ground substance – facilitates diffusion

*note: elastic fibers need a special silver stain to be visualized

Question 7

How does the dermis control hemostasis?

Q

Answer 7

via structure called Sucquet-Hoyer canal:
a smooth muscle derived valve-like structure, blood may be directed toward the skin during overheating, or away from the skin in hypothermia.

Question 8

How does the dermis modulate inflammation/leukocyte trafficking?

Answer 8

via the expression of intracellular adhesion molecules (ICAMs):
white blood cells begin the process of first adherence and rolling, and second diapedesis, so that they may exit the vasculature to fight infection in the skin and soft tissue

Question 9

Types of Collagen relevant to the skin

Answer 9

I, III, IV, VII

Trick on how to learn this:
I+ 3 = 4
3+4 = 7

Question 10

Collagen I

Answer 10

> 85 wt. % of the adult dermis. ○ Major component of bone.

Question 11

Collagen III

Answer 11

Q

○ Large part of the fetal dermis but is not a major portion of the adult dermis.

Question 12

Collagen IV

Answer 12

○ Found in high concentration in the “basement membrane zone” which is present in the dermoepidermal junction.

More prominent around vessels and this explains the vascular fragility in some forms of Ehlers-Danlos syndrome

Question 13

Collagen VII

Answer 13

Found in the anchoring fibrils which are used by the body to attach the epidermis to the dermis.

Question 14

Synthesis of Collagen mechanism:

Answer 14

1. . Large precursor, PROcollagen, is synthesized within fibroblasts (intracellularly)
   ○ Procollagen consists of 3 separate chains of proteins arranged in α-helical structure
   ○ Consists of repeating glycine residues
2. . Excreted extracellularly
3. Cleaved enzymatically into TROPOcollagen
4. . Tropocollagen aggregates,becomes cross-linked
5. . Cross-linking dependent upon vitamin C (co-factor)

Question 15

List the components and describe the function of the ground substance of the dermis.

Answer 15

Ground substance: “Pie filling” of the dermis
- Protein-Sugar moieties of two glycosaminoglycans: hyaluronic acid and dermatan sulphate.
- “Glued” together with fibronectins
○ Fibronectins also renew the ground substance which is constantly being destroyed by hyaluronidase
- Gel-like mass that functions like sponge:
○ Intercalates between and amongst the collagen bundles, elastic fibers, and appendageal structures of the dermis.

Question 16

Scurvy vs Ehlers-Danlos syndrome (EDS)

Answer 16

Scurvy is an acquired disease of collagen production.

Ehlers-Danlos syndrome (EDS): a group of related congenital disorders of collagen synthesis

Question 17

Ehlers-Danlos syndrome (EDS): symptoms

Answer 17

• skin hyperextensibility
• joint hypermobility
• tissue fragility
• poor wound healing
• It is tempting to want to believe that EDS is due to a disorder in elastic fibers, but this is not the case; the disorder is due to abnormally formed collagen. .

Question 18

Corkscrew hairs and perifollicular hemorrhage is found in what disease?

Answer 18

Scurrrrvy

Question 19

leukocytoclastic vasculitis:

Answer 19

○ common disease involving the post-capillary venules
- Type III hypersensitivity:

The deposition of immune complexes leads to inflammation.
Neutrophils attach to the vessel wall and degranulate yielding damage and the extravasation of red blood cells into the dermis. This process of fibrinoid deposition in the vessel walls, with infiltrating neutrophils and neutrophil debris is called leukocytoclasia.

Question 20

Vasculitis manifesting as “palpable purpura”

Answer 20

○ Combination of inflammation and hemorrhage

○ It is palpable because of the inflammation, and it is purpuric due to the extravasation of RBCs.

Question 21

Congenital insensitivity to pain

Answer 21

○ Mutation in NTRK1

○ They cannot feel the common danger signs which normally lead to protective responses.

Question 22

Two types of hair:

Answer 22

1) Terminal hair (eg. scalp) 
• dark 
• thick 
• coarse
2) Vellus hair (eg. Ears) 
• fine 
• thin 
• apigmented

Question 23

Eccrine glands

• what is it?
• Fxn?

Answer 23

• General sweat glands
• Primary fxn: thermoregulation (cooling effects of evaporation)
○ Forehead, upper cutaneous lip, and palms/soles.

Question 24

What part of the nervous system is sweating controlled by?

Answer 24

• Sweating controlled by sympathetic portion of ANS (triggered via acetylcholine secretion)
○ More people sweat in stress!
○ IT IS CRITICAL TO RECOGNIZE that even though sweating is mediated by the sympathetic portion of the ANS it is triggered via acetylcholine secretion. Acetylcholine is a chemical otherwise associated with the parasympathetic nervous system.

Question 25

Apocrine glands

• location?
• what is it?
• Aprocine gland sweat vs the sweat from eccrine glands?

Answer 25

-Located only in the axillary and anogenital area.
- Consist of a coiled portion deep in the dermis, and a straight duct which traverses the dermis and empties into the hair follicle
○ Structure similar to eccrine glands:
- Sweat is stickier, odorless (initially), then smells upon contact with skin flora

Question 26

Apoeccrine glands

• what is it?
• where is it located?
• role?
• Apoeccrine gland vs eccrine?

Answer 26

• Hybrid sweat glands
• Located mainly in axilla
• Likely play a role in axillary hyperhidrosis

Apoeccrine glands secrete nearly ten times as much sweat as eccrine glands

Question 27

Sebaceous glands are the classic example of a _________________

Answer 27

holocrine gland

Question 28

“Prickly heat”

Answer 28

Miliaria
• Blocked sweat ducts
• Acquired disorder of eccrine function

Question 29

“Anhidrotic Ectodermal Dysplasia”

Answer 29

• Mutation in EDA gene

* Abnormal eccrine development

Question 30

Solar Elastosis

Answer 30

Acquired disorder of elastic fibers
• Sun-damaged elastic fibers
• Basophilic within superficial dermis
• Indicates tissue is from older person in a sun-exposed site

Question 31

Pseudoxanthoma Elasticum (PXE)

Answer 31

caused by a mutation in MDR gene
• Net result - calcified, brittle elastic fibers
• Assoc with “plucked chicken” skin