1. The epidermis consists of five layers. The two most superficial
layers (the stratum corneum and lucidum) contain nonviable keratinocytes.
2. Collagen III provides tensile strength to the dermis and epidermis.
3. Adult dermis contains a 4:1 ratio of type I:type III collagen.
4. Of the congenital skin disorders, only pseudoxanthoma elasticum
and cutis laxia are responsive to surgical rejuvenation.
5. Hemangioma is the most common cutaneous lesion of infancy and
a large majority spontaneously involute (resolve) past the first
year of patient age.
6. Basal cell carcinoma (BCC) is the most common form of skin cancer
and nodular BCC is the most frequent form of this tumor.
7. Breslow thickness is the most important prognostic variable predicting
survival in those with cutaneous melanoma.
As the largest human organ, the skin is one of the most complex and
physiologically underappreciated elements of our bodies. Beneath
its uniform appearance, the skin demonstrates profound regional
variation due to the highly structured organization of many different
cell types and dermal elements. Although primarily valued as a protective
barrier allowing interface with our surroundings, the structure
and physiology of the skin is complex and fascinating. As an environmental
buffer, the skin protects against a vast array of destructive forces:
The structural integrity of the epidermis creates a semipermeable
barrier to chemical absorption, prevents fluid loss, protects against
penetration of solar radiation, rebuffs infectious agents, and dermal
durability resists physical forces. In addition, the skin’s
ability to regulate body heat makes it the body’s primary
thermoregulatory organ. The relative ease of analyzing skin specimens
has made the skin one of the best-studied tissues of the human body.
Not only does this fascinating organ form the primary focus of the
subspecialties of plastic surgery and dermatology, but it also has
driven research in a broad number of fields, including immunology,
transplantation, and would healing.
Anatomically, the skin may be divided into three layers: the epidermis,
basement membrane, and dermis.1–3 With
very little extracellular matrix (ECM), the epidermis is composed
primarily of specialized cells that perform vital functions. Sandwiched
between epidermal and dermal structures, the basement membrane anchors
these layers together.1–3 This membrane
fulfills many biologic functions, including tissue organization,
growth factor reservoir, support of cell monolayers during tissue
development, and semipermeable selective barrier. In addition to
its role in providing soft-tissue durability, the dermis is primarily
composed of a dense ECM that provides support for a complex network
of nerves, vasculature, and adnexal structures.3,4 The
ECM is a collection of fibrous proteins and associated glycoproteins
embedded in a hydrated ground substance of glycosaminoglycans and
proteoglycans. These distinct molecules are organized into a highly ordered
network that is closely associated with the cells that produce them.
In addition to providing the architectural framework that imparts
mechanical support and viscoelasticity, the ECM can regulate the ...