First Digit: Solids. The first digit indicates the level of protection that the enclosure provides against access to hazardous parts (e.g., electrical conductors, moving parts) and the ingress of solid foreign objects.s defined in international standard IEC 60529, it classifies the degrees of protection provided against the intrusion of solid objects (including body parts like hands and fingers), dust, accidental contact, and water in electrical enclosures.
The mucosa is composed of three components (inner to outer): a non-keratinizing stratified squamous epithelium, a lamina propria and the muscularis muscosa. The submucosa is composed of loose connective tissue, blood vessels, lymphatics, lymphoid follicles, the meissner plexus of nerves and submucosal glands.
This is the underlying layer of areolar connective tissue. It contains blood vessels, nerve endings, lymphatic vessels, and cells of the immune system. It provides mechanical and metabolic support for the epithelium and protection as part of the immune system.he outer boundary of the mucosa is often marked by a band of smooth muscle arranged in two thin concentric layers, an inner circular layer and outer longitudinal layer. Contraction of the muscularis mucosae agitates the epithelium and alters its shape.