American Academy of Professional Coders (AAPC) 2025 – 400 Free Practice Questions to Pass the Exam

The correct answer is based on the classification of membranes in the human body, which are categorized into various types based on their structure and function. The key types of membranes include:

1. **Mucous membranes** (mucosa) – These line body cavities that open to the outside, such as the respiratory, digestive, and urogenital tracts. They produce mucus, which keeps these surfaces moist and helps trap pathogens.

2. **Serous membranes** (serosa) – These line closed cavities and cover organs. They consist of a layer of simple squamous epithelium called mesothelium and underlying connective tissue, producing serous fluid to reduce friction between moving organs.

3. **Cutaneous membrane** (skin) – This is the largest membrane and serves as the outer protective layer of the body, composed of the epidermis and dermis.

4. **Synovial membranes** – These line the synovial joints and secrete synovial fluid, facilitating smooth movement between the articular cartilages.

Each of these four types plays a critical role in the body's homeostasis and protection, making the total number of distinct membrane types in the human body four. Understanding these membrane types is essential for studying