Which component is part of the wall of the GI tract?

The mucous membranes are an integral part of the wall of the gastrointestinal (GI) tract. These membranes line the lumen of the GI tract from the mouth to the anus and are composed of epithelial tissue that secretes mucus, which plays several key roles. The mucus serves as a lubricant, facilitates the movement of food through the digestive system, and protects the underlying tissues from the abrasive nature of food and from digestive enzymes. Additionally, the mucous membranes are involved in the absorption of nutrients.

In contrast, the other options do not form part of the GI tract wall. The subcutaneous layer is a layer of connective tissue that primarily supports skin and is not found in the walls of the GI tract. The serous membrane, while associated with body cavities and organs, does not directly make up the wall of the GI tract; instead, it provides a protective outer lining to some abdominal organs. The dermal layer refers specifically to skin structure and is not relevant to the internal architecture of the GI tract.