Dermis and Adnexal Structures Flashcards
Does the epidermis contain blood vessels?
No. Only the dermis
What two zones make up the dermis?
Which one is more superficial?
- Papillary dermis & Reticular dermis
- Papillary dermis is more superficial
What is the dermal matrix composed of?
Collagen fibers, elastic fibers and ground substance
What is the major function of the epidermis?
Protection
The dermoepidermal junction consists of interlocking projections. What are their names?
Downward projections of the epidermis = epidermal rete
Upward projections of the dermis = dermal papillae
What are the two functions of the dermoepidermal junction?
- Strength of adherence
2. Increases the surface area
Dermoepidermal junctions are responsible for what feature on the hands and feet?
Fingerprints
What is the function of collagen?
Provides essentially all the tensile strength of the skin
What is the role of Collage I?
Comprises >85% of adult dermis
Major component of bone
What is the role of Collagen III?
Fetal dermis- Why fetal skin doesn’t tend to scar
What is the role of Collagen IV?
Found in the basement membrane zone (present in the dermoepidermal junction)
More prominent around vessels
What is the role of Collagen VII?
Found in anchoring fibrils which are used by the body to attach the epidermis to the dermis
Where is procollagen synthesized?
INTRACELLULARLY in fibroblasts
What consists of three separate chains of proteins arranged in an alpha-helical structure?
Procollagen
Chains consists of three repeating chains what are they?
GLY-X-Y
X= Proline
Y= Hydroxyproline
Where is collagen assembled?
Extracellularly
Name one cofactor needed for assembly of collagen fibrils
Absorbic acid (Vitamin C)
A patient comes in with a chief complaint of:
-Inadequate wound healing
-Abnormal hair growth
-Fragile blood vessels
-Teeth falling out
What should be on you differential diagnosis?
Scurvy! This is caused by vitamin C deficiency»_space;>abnormal collagen production
Name one congenital abnormality that effects collagen synthesis.
Ehlers-Danlow Syndrome
Name 4 major clinical features of Ehlers-Danlos Syndrome.
- Skin hyperextensiblity
- Joint hypermobility
- Tissue fragility
- Poor wound healing
What is the function of elastic fibers?
Provide resiliency
Are collagen fibers eosinophilic or basophilic?
Eosinophilic
What stain must you use to visualize elastic fibers?
Silver stain because elastic fibers are argyrophilic and appear black
What is one acquired disorder associated with elastin?
Solar elastosis- accumulates significant sunlight exposure»> degradation of elastic fibers
How does solar elastosis change the microscopic appearance of elastin?
Argyrophilic»_space; Basophilic
What causes pseudoxanthoma elasticum (PXE)?
Inherited elastic disorder caused by mutation in gene encoding part of “multidrug resistance complex”
Elastic fibers become enlarged, tangled, and calcified
What is the role of “multidrug resistance complex”?
Pump compounds out of the cells (resistance to certain chemotherapy)
A patient comes in with the skin of the flexural areas of the body having a plucked chicken appearance, hypertension and bleeding disorders. What should be on the DDX?
PXE
Ground substance consists principally of two glycosaminoglycans. What are they?
Hyaluronic acid & Dermatan sulphate
What are fibronectins?
gel-like mass functions like a sponge.
Helps facilitate nourishment
What is the role of fibroblasts in ground substance?
What is the role of hyaluronidase in ground substance?
Fibroblasts- Produce ground substances
Hyaluronidase- destroys ground substances
What two vascular structures are found in the dermis?
Superficial and deep vascular plexi
What are the three roles of the dermal vascular supply?
- Wound healing
- Homeostasis
- Modulation of inflammation/leukocyte trafficking
What is Sucquet-Hoyer canal?
Smooth muscle derived valve-like structure, blood may be directed towards skin during overheating or away during hypothermia
What is Auspitz sign?
Pinpoint bleeding after the forceful removal of psoriasis plaque
What is a verruca?
Benign, virally induced neoplasms that require an increased blood supply
Leukocytoclastic vasculitis is caused by immune complexes depositing in post-capillary venules. What Gell and Coombs reaaction pattern is that?
Type III- immune complex mediated
What is the pathogenesis of leukocytoclastic vasculitis?
- Immune complexes deposit in the post-capillary venule
- Neutrophils attach to vessel and degranulate
- Yielding damage and extravasation of red blood cells
What is the manifestation of leukocytoclastic vasculitis?
Palpable purpura which is not blanchable
What is the function of the nervous system in the dermis?
Protect and inform
Free nerves are responsible for what two sensations?
Pain and itch
What are the physical characteristic of afferent pruritus nerves?
Unmyelinated C fibers with a slow conduction rate
True or False:
Itch and pain are different and independent sensory modalities.
True
What is the function of Pacinian corpuscles?
They are onion shaped nerves involved in pressure and vibratory sensations
What is the function of Meissner’s corpuscles?
They are pine-cone shaped nerves involved in fine touch and tactile discrimination
Where is the highest concentration of Meissner’s corpuscles?
Distal aspects of the digits
Mutations in the neurotrophic tyrosine recetor kinase I (NTRK1) gene results in what condition?
Congenital insensitivity to pain + co-existing anhidrosis (inability to sweat)
What are the two types of hair?
Terminal and Vellus
Where are terminal hairs found?
Scalp, a man’s beard area and possibly chest/back, and pubic area
What is an arrector pili muscle?
Small, smooth-muscle which, when activated by the autonomic nervous system, brings the hair into a more erect position
What are the three parts of the hair follicle?
Infundibulum- Upper third
Isthmus- Middle third
Matrical area- Lower third
the primitive ectodermal germ (PEG) consists of three bulges. What are they and what do they encode for?
Lower bulge- attachment for arrector pili
Middle bulge- sebaceous gland
Upper bulge- apocrine gland
What are the three phases of hair growth?
Anagen-growth phase
Telogen- resting phase
Catagen- transition phase
What promotes alopecia?
The conversion of testosterone to 5-dihydrotestosterone
What blocks the conversion of testosterone to 5-dihydrotestosterone?
finasterride, a 5-alpha-reductase inhibitor
What type of gland are sebaceous glands?
Holocrine
Where does a sebaceous gland release its sebum?
Hair follicle
What is the function of eccrine glands?
Thermoregulation
Are eccrine glands derived from primitive ectodermal germ?
No
Sweating is mediated by the sympathetic portion of the autonomic nervous system, but triggered by what?
Acetylcholine
Where are apocrine glands located?
Axillary and anogenital area
Name three specialized variants of apocrine glands.
- Moll’s glands on the eyelids
- Cerumen (ear wax) glands
- Lactation glands of the breast
What secretion occurs through decapitation?
Apocrine
What is chromohidrosis?
Colored sweat
Where are the appoeccrine glands primarity found?
Axilla. Cholinergic stimuli
How can you treat hyperhidrosis?
Botulinum toxin A (Botox) which blocks the release of acetylcholine
