Absorption

Summary and Exam Tips for Absorption

Absorption is a subtopic of Human Nutrition, which falls under the subject Biology in the Cambridge IGCSE curriculum. The process of absorption involves the transport of molecules from digested food into the blood and lymph. The small intestine is the primary site for nutrient absorption, where glucose and amino acids enter the bloodstream, while fatty acids and glycerol are absorbed into the lymphatic system. Although both the small intestine and the colon absorb water, the small intestine accounts for approximately 80% of water absorption.

The small intestine is uniquely designed for efficient absorption due to its numerous villi and microvilli, which significantly increase the internal surface area. Each villus is microscopic and has a thin, one-cell-thick wall that facilitates easy diffusion of nutrients. Blood capillaries within the villi transport dissolved glucose and amino acids, while lacteals carry glycerol and fatty acids via the lymphatic system. The villi's structure, with its excellent blood supply and thin linings, is crucial for maximizing absorption efficiency.

Exam Tips

• Understand the Structure and Function: Be familiar with how the structure of a villus relates to its function in absorption. This is a common focus in exam questions.
• Key Areas of Absorption: Remember that the small intestine is the main site for nutrient and water absorption, with the colon also playing a role in water absorption.
• Villi and Microvilli: Highlight the importance of villi and microvilli in increasing the surface area for absorption. This is often tested in exams.
• Role of Capillaries and Lacteals: Know the roles of capillaries in transporting glucose and amino acids, and lacteals in carrying fatty acids and glycerol.
• Practice Questions: Regularly practice questions related to the structure and function of the small intestine to reinforce your understanding.