2025 Key Stage 3 (KS3) Biology Practice Test – The Complete Guide to Mastering Your Exam Success!

The digestive system is the organ system specifically designed to break down food into smaller molecules that the body can absorb and use for energy, growth, and cellular repair. It includes several key organs such as the mouth, esophagus, stomach, intestines, liver, pancreas, and gallbladder, each playing a vital role in the digestion process. For example, the mouth begins digestion with chewing and saliva, the stomach further breaks it down with acids and enzymes, and the intestines absorb the nutrients into the bloodstream.

In contrast, the circulatory system is responsible for transporting blood, nutrients, gases, and waste products throughout the body. The respiratory system is focused on gas exchange, primarily oxygen intake and carbon dioxide expulsion, which are crucial for cellular respiration but do not digest food. Lastly, the nervous system manages signals from the body and coordinates actions but does not directly partake in the process of digestion. Thus, the digestive system is the specialized system for this essential function.