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.
Composite or combination wound dressings, are multi-layer dressings that can be used as primary- or- secondary wound dressings. Most composite dressings have three layers. The inner contact layer is non-adherent, preventing trauma to the wound bed during dressing changes.