Dermis and Adnexal structures Flashcards
What structures are within the dermis?
- blood vessels
- nerves
- adnexal structures (hair, glands, etc.)
What are the two layers of the dermis?
- papillary dermis
2. reticular dermis
What is the purpose of the dermis?
Structural & physiologic support network
Provides major tensile strength of skin
Which layer is more superficial?
Papillary dermis
Which layer has thin collagen fibers? Which has thick?
Thin: papillary
Thick: reticular
Which layer has elastic fibers?
Reticular dermis
What are the three building blocks of the dermis? And what do they do?
- Collagen – forms the tensile strength
- Elastic fibers– allow for resilience
- Ground substance– facilitates diffusion
Which type of collagen is most prevalent in the dermis?
Collagen I: >85% weight of dermis
What are the steps of collagen production
- PROcollagen synthesized within fibroblasts
- Excreted extracellularly
- Cleaved enzymatically into TROPOcollagen
- Tropocollagen aggregates, becomes cross-linked
Why is vitamin C necessary for collagen production
Cross-linking (last step) is dependent upon the co-factor vitamin C
What causes scurvy?
Vitamin C deficiency resulting in decreased mature collagen
This can lead to hemorrhage because of decreased support of blood vessels
What is a congenital disorder of collagen production?
Ehlers-Danlos Syndrome= a family of disorders based on erroneous collagen synthesis
What are symptoms of Ehlers-Danlos syndrome?
• Mutations at various stages of collagen production yield findings such as: – hyperextensible skin – hyperextensible joints – fragile blood vessels – poor wound healing
What is solar elastosis?
An acquired disorder from sun damage to elastic fibers
What is a congenital disorder of elastic fibers?
Pseudoxanthoma Elasticum
• Caused by a mutation in MDR gene which causes calcified, brittle elastic fibers
“PLUCKED CHICKEN SKIN”
What is the ground substance?
The “pie filling”
- gelatinous substance that holds and absorbs 10,000x its weight in water
- held together by fibronectins
What are two GAGs (glycosaminoglycans) within the ground substance?
– hyaluronic acid
– dermatan sulphate
These were highlighted in the slides, so they may be important
What are the two important types of nerves?
• Type A- heavily myelinated, conduct rapidly
-carries touch, proprioception, muscle stretch receptors, pain
• Type C fibers- unmyelinated, slow-conducting
-convey sensation of diffuse, dull, non-localizing
– temperature and itching sensations
What are two disorders of capillary loops?
Psoriasis, verruca
What can cause an itch?
– dry skin (xerosis)
– infection (HIV)
– infestation (scabies or lice)
– metabolic disorders (renal failure)
What is vasculitis?
Inflammation of the capillaries and venules
“Palpable purpura” - combination of inflammation and hemorrhage
What’s the difference between Meissner’s and Pacinian corpuscles? Which one’s pine cone/ onion like?
They are both specialized skin receptors
Meissners: “pine- cone” like, involved in fine touch, highest density on pulps of digits, located in DEJ (dermis, epidermis junction
Pacinian: “onion” like, involved in pressure and vibration, highest density on genitals, located in the dermis,
What is the rule of three’s in hair? (hint: growth cycles)
Hairs randomly engaged in 1 of 3 cycles
– anagen (growth) – 85%
– telogen (rest) – 10-15%
– catagen (involution) – 1-5%
• Cycles follow a “basic rule of threes”
– anagen – 3 years
– telogen – 3 months
– catagen – 3 weeks (or less)
What is androgenic hair loss?
“male-pattern” baldness
Caused by conversion of testosterone to DHT
