Only dermis is vascularized. Nutrients reach epidermis by diffusing through the tissue from the blood vessels. Underneath dermis is hypodermis (superficial fascia), also called subcutaneous tissue which is composed of loose connective tissue (mostly areolar and adipose).
A collagen dressing is a type of wound dressing that is made with a form of collagen to aid in the body's healing processes. Collagen is a category of structural proteins that are naturally present in almost every part of the human body and are especially common in connective tissue.
There are a number of different collagen dressings available that use a variety of carriers and combining agents such as gels, pastes, polymers and oxidised regenerated cellulose (Brett, 2008). The collagen contained in these products also varies in type and source.