Which organs are part of the digestive system?

The selection of liver, stomach, mouth, and pancreas as part of the digestive system is accurate because each of these organs plays a critical role in the overall process of digestion and nutrient absorption.

The mouth is the first organ involved in digestion, where mechanical breakdown of food occurs through chewing, and enzymes in saliva begin the chemical breakdown of carbohydrates. The stomach further processes food by mixing it with gastric juices, which contain acids and enzymes that break down proteins. The pancreas is essential for digestion as it produces digestive enzymes that are secreted into the small intestine, aiding in the breakdown of carbohydrates, proteins, and fats. Lastly, the liver produces bile, which is stored in the gallbladder and released into the small intestine to help emulsify fats for easier absorption.

The other options represent organs or systems that do not have a direct role in digestion, such as the lungs and heart, which are involved in the respiratory and circulatory systems, and the kidneys and bladder, which are part of the urinary system. Skin and nails are also not associated with the digestive process. Thus, the choice of liver, stomach, mouth, and pancreas is correctly identified as integral components of the digestive system.