Page 21 - APPENDIX B: Trials Investigating the Management of Acute Radiation-Induced Skin Reactions Reading Qualitative Research

21
WOUND CARE

The epidermis is the outermost superficial layer of skin. It includes the outer cornified

layer and the deeper basal layer that is constantly being renewed in response to the normal

shedding of the cornified layer through a balanced production of new cells from the basal layer.

The basal layer of the epidermis encompasses germinal or stem cells that divide and differentiate

into mature skin cells. About 10% of basal cells undergo mitosis each day as outer cells of the

cornified layer are shed; they are substituted by newly differentiated cells from the basal layer.

This normal course comprises of both the proliferation and differentiation or maturation of skin

cells to entirely replace epidermal layer approximately every four weeks (McQuestion, 2011;

Sparks, 2007).

The dermis underlying the epidermis is the thickest part of the skin (1-3mm). The

dermis contains the support structures including blood vessels, nerves, glands and hair follicles

(Sparks, 2007). The dermis is responsible for the nutrition of the epidermis via a dense network

of arterial and venous capillaries and some larger vessels (Nouri, 2008). The dermis provides the

skin with its elasticity and strength; it also plays a role in thermoregulation, sensory perception

and defense against injury and disease. The epidermis and the dermis rest on the hypodermis

that is the fatty subcutaneous layer which provides insulation for the body (Nouri, 2008; Sparks,

2007).

The pathophysiology of radiation induced dermatitis is a sequence of radiation injury and

resulting inflammatory response that can occur at both the entrance and exit site of the irradiation

(Hymes, Strom, & Fife, 2006). Ionizing radiation damages the mitotic capability of stem cells

within the basal layer preventing the process of repopulation and weakening the integrity of the

skin (Hymes, Strom, & Fife). The skin is very sensitive to radiotherapy with basal layer damage

occurring, when the cumulative dose reaches 20 Gy and it becomes more noticeable by week two