OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What are tiny projections on the surface of the small intestine called?

1. Microvilli

2. Glycocalyx

3. Villi

4. Filaments

The correct answer is: Villi

The tiny projections on the surface of the small intestine are called villi. These finger-like structures significantly increase the surface area available for absorption of nutrients from digested food. Each villus contains a network of blood vessels and lymphatic vessels, allowing for efficient transport of nutrients into the bloodstream and lymphatic system. This design enhances the digestive efficiency of the small intestine, making it possible for the body to absorb more nutrients effectively. Microvilli are even smaller projections found on the epithelial cells of the villi, further increasing the surface area, but they are not the primary structures referred to in this question. The glycocalyx is a carbohydrate-rich zone on the cell surface involved in protection and recognition processes, not specifically in nutrient absorption. Filaments typically refer to thin, thread-like structures and do not describe the anatomical features of the small intestine. Thus, the term that best describes the tiny projections on the surface of the small intestine is villi.