DD Dermis and adnexal structures Flashcards
What does the dermis contain?
- It’s got the goods!
blood vessels, nerves, and cutaneous appendages (hairs, sweat glands/ducts, etc.)
- needs a way to share it
Where is the dermis located?
Beneath the epidermis and above the subcutaneous tissue
How is the vascular supply of the dermis broken up?
○ Vascular supply is broken into 2 plexus:
- Superficial horizontal plexus - Deep horizontal plexus
adnexal (appendageal) structures: examples
– hair follicles – eccrine glands – apocrine glands – apoeccrine glands – sebaceous glands – n/v
Which one has thin collagen bundles: papillary dermis of reticular dermis?
papillary dermis
reticular has thick collagen bundles with visible elastic fibers
- Building blocks of the dermis:
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
How does the dermis control hemostasis?
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.
How does the dermis modulate inflammation/leukocyte trafficking?
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
Types of Collagen relevant to the skin
I, III, IV, VII
Trick on how to learn this:
I+ 3 = 4
3+4 = 7
Collagen I
> 85 wt. % of the adult dermis. ○ Major component of bone.
Collagen III
○ Large part of the fetal dermis but is not a major portion of the adult dermis.
Collagen IV
○ 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
Collagen VII
Found in the anchoring fibrils which are used by the body to attach the epidermis to the dermis.
Synthesis of Collagen mechanism:
- . 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 - . Excreted extracellularly
- Cleaved enzymatically into TROPOcollagen
- . Tropocollagen aggregates,becomes cross-linked
- . Cross-linking dependent upon vitamin C (co-factor)
List the components and describe the function of the ground substance of the dermis.
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.
Scurvy vs Ehlers-Danlos syndrome (EDS)
Scurvy is an acquired disease of collagen production.
Ehlers-Danlos syndrome (EDS): a group of related congenital disorders of collagen synthesis
Ehlers-Danlos syndrome (EDS): symptoms
- 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. .
Corkscrew hairs and perifollicular hemorrhage is found in what disease?
Scurrrrvy
leukocytoclastic vasculitis:
- involves what type of vessels?
- type of hypersensititivity?
- process
○ 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.
Vasculitis manifesting as “palpable purpura”
○ Combination of inflammation and hemorrhage
○ It is palpable because of the inflammation, and it is purpuric due to the extravasation of RBCs.
Congenital insensitivity to pain
○ Mutation in NTRK1
○ They cannot feel the common danger signs which normally lead to protective responses.
Two types of hair:
1) Terminal hair (eg. scalp)
• dark
• thick
• coarse
2) Vellus hair (eg. Ears)
• fine
• thin
• apigmented
Eccrine glands
- what is it?
- Fxn?
• General sweat glands
• Primary fxn: thermoregulation (cooling effects of evaporation)
○ Forehead, upper cutaneous lip, and palms/soles.
What part of the nervous system is sweating controlled by?
• 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.
