Final answer:
The lower layer of mucus in the nasal cavity is known as the respiratory epithelium, which is part of the mucous membranes lined with cilia and goblet cells, playing a critical role in trapping debris and harboring immune defenses.
Step-by-step explanation:
The mucus secreted by the mucous membranes of the nose is part of the body’s defense system against pathogens. The mucous membranes are coated with secretions from mucous glands, with a specialized structure to optimize their defensive role. The lower layer of the mucus in the nose, responsible for trapping microbes and debris, is known as the respiratory epithelium. This epithelium contains goblet cells that produce mucus and is lined with cilia that sweep the mucus and debris towards the throat to be swallowed. This process is part of the mucociliary escalator effect which is essential in preventing inhaled microorganisms from entering the lower respiratory tract.
Furthermore, the mucous layer is also equipped with immune defenses such as lysozyme enzymes and defensins with antibacterial properties, and immune cells that patrol the area. The moist nature of the epithelium also functions to warm and humidify incoming air. Overall, the mucous membrane's lower layer, the respiratory epithelium, plays an important role in maintaining respiratory health.