Certified Surgical Technologist (CST) Practice Exam

What layer of the gastrointestinal tract is primarily responsible for absorption and secretion?

1. Mucosa

2. Serosa

3. Muscularis

4. Submucosa

The correct answer is: Mucosa

The mucosa is the innermost layer of the gastrointestinal tract and plays a crucial role in digestion, absorption, and secretion. This layer contains epithelial cells that absorb nutrients and secrete digestive enzymes as well as mucus, which aids in the smooth passage of food. It provides a barrier against pathogens while facilitating the absorption of water, vitamins, and nutrients into the bloodstream. In contrast, the other layers serve different functions. The serosa is the outermost layer that provides protection and support to the digestive organs. The muscularis layer is responsible for the peristaltic movements that propel food through the gastrointestinal tract, while the submucosa contains blood vessels, nerves, and connective tissue, primarily providing support and nourishment to the mucosa and assisting in regulation but not directly involved in absorption or secretion. Thus, the mucosa is distinctively positioned as the primary layer dedicated to these critical functions.