Which of the following structures are fingerlike extensions of the intestinal mucosa that increase the surface area for absorption?

• A. Cristae
• B. Microtubules
• C. Cilia
• D. Villi

Answer: (D)

Verified step by step guidance

1. Understand the function of the intestinal mucosa: The intestinal mucosa is the innermost layer of the gastrointestinal tract and is specialized for nutrient absorption. To maximize absorption, it has structures that increase its surface area.
2. Review the term 'villi': Villi are small, fingerlike projections of the intestinal mucosa. They are covered with epithelial cells and contain blood vessels and lymphatic vessels to transport absorbed nutrients.
3. Eliminate incorrect options: Cristae are folds in the inner membrane of mitochondria, not related to the intestinal mucosa. Microtubules are components of the cytoskeleton, involved in cell structure and transport, not absorption. Cilia are hairlike structures on the surface of some cells, but they are not involved in increasing the surface area of the intestinal mucosa.
4. Connect the structure to its function: Villi increase the surface area of the intestinal mucosa, allowing for more efficient absorption of nutrients from digested food.
5. Conclude that the correct answer is 'villi' based on their structure and function in the intestinal mucosa.