A Level Biology Practice Exam

What is the primary function of mucous membranes?

1. To provide structural support to organs

2. To secrete a sticky mucus that lines body tracts

3. To absorb nutrients from digested food

4. To initiate immune responses to pathogens

The correct answer is: To secrete a sticky mucus that lines body tracts

The primary function of mucous membranes is to secrete a sticky mucus that lines various body tracts. This mucus serves several essential roles, including providing lubrication and protection to the underlying tissues. In the respiratory system, for example, mucus traps dust, pathogens, and other foreign particles, preventing them from entering the lungs. In the digestive system, it facilitates the movement of food along the gastrointestinal tract and protects the lining of the intestines from abrasive materials and digestive enzymes. While mucous membranes can play roles in nutrient absorption and in initiating immune responses, these are not their primary functions. The secretion of mucus is crucial for maintaining the health and function of the epithelial surfaces they cover, contributing enormously to overall bodily protection and homeostasis.