|
adventitial dermis: combined anatomic unit of papillary and peri-adnexal dermis; thin, haphazardly arranged collagen fibers
| fibers: | can be seen with naked eye |
| fibrils: | can be seen with light microscope |
| microfibrils: | can be seen with EM only |
elastic fibers:
| • | composed of elastin core wrapped by microfibrils composed of fibrillin |
| • | Marfan’s syndrome = any one of a variety of defects in the fibrillin gene |
| • | in papillary dermis: thin and perpendicular to epidermis |
| • | in reticular dermis: thicker and mostly parallel to epidermis |
fibroblast:
| • | builder cell of the dermis |
| • | produces all of the fibrillar components as well as the ground substance |
ground substance of the dermis:
| • | mostly acid mucopolysaccharides: hyaluronic acid, chondroitin sulfate, dermatan sulfate |
| • | in certain pathologic states, the amount of acid mucopolysaccharides in the dermis increases |
| • | this deposit is widespread in myxedema |
| • | localized in focal mucinosis |
collagen
type I = reticular dermis
type II = cartilage only
type III = papillary dermis, fetal skin, blood vessels
type IV = basal lamina
type VII = anchoring fibrils
type III collagen:
| • | most of the collagen in the fetal dermis is type III (reticulum fibers) (vs. type I in adults) |
| • | reticulum fibers are the first seen in fetal development, and are found also in healing wounds, granulomas, and fibroblastic tumors |
| • | type III collagen is defective in type IV Ehlers-Danlos, which is characterized by a thin dermis and arterial rupture |
|
|