ISSA Nutritionist Practice Exam 2025 – Comprehensive All-In-One Guide to Exam Mastery!

Most nutrient absorption occurs in the small intestine due to its unique structure and function. The small intestine is composed of three segments: the duodenum, jejunum, and ileum. This organ has a large surface area because it is lined with villi and microvilli, which are tiny, finger-like projections that increase the absorptive surface.

As chyme enters the small intestine from the stomach, it is mixed with digestive juices that help break down food into smaller molecules. Nutrients such as carbohydrates, proteins, and fats are then absorbed through the walls of the small intestine into the bloodstream. This allows the nutrients to be transported to various tissues and organs throughout the body where they can be utilized for energy, growth, and repair.

The stomach primarily focuses on breaking down food through acid and enzymes, while the large intestine's main role is to absorb water and electrolytes and to prepare waste for elimination. The esophagus serves only as a passageway for food to travel from the mouth to the stomach and is not involved in absorption. Thus, it is clear that the small intestine is the primary site for nutrient absorption in the digestive system.