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.