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.
Mucous membrane (mucosa) Areolar connective tissue; interlaced with the muscular coat. This layer contains blood vessels, nerves, and in some regions, glands. A tumor, which has spread to this layer, can metastasize to the rest of the body via the lymphatics and blood vessels. Muscular coat (muscularis propria) Three layers: inner longitudinal, middle circular, and outer longitudinal. Serous coat (serosa)