Question

A young infant may be feeding entirely on mother's milk which is white in colour but the stools which the infant passes out is quite yellowish. The yellow colour of stool is due to (a) bile pigments passed through bile juice (b) undgested milk protein casein (d) pancreatic juice poured into duodenum (c) intestinal juice

Short answer

The yellow color of the stool is due to bile pigments passed through bile juice.

Step-by-step solution

Understanding the Digestive Process

Recognize that the color of stool is affected by various components that are either digested or excreted during the digestive process. This process begins in the mouth and ends in the intestine, where waste products are formed into stool.

Identifying the Source of Yellow Color

Note that the yellow color in the stool is unlikely to be caused by undigested food or color of the food itself as mother's milk is white. Bile pigments, which are produced by the liver and stored in the gallbladder, are known to change color as they are broken down in the digestive process, often giving stool a yellow or brown color.

Understanding the Role of Bile Pigments

Recognize that bile pigments, such as bilirubin, are by-products of the breakdown of red blood cells and are present in bile juice. These pigments travel through the digestive tract, being chemically altered along the way, resulting in a characteristic yellow color in infants' stool.

Eliminating Other Options

Understand that while pancreatic and intestinal juices contribute to digestion, they do not impart a yellow color to the stool. Undigested milk protein casein is also not responsible for the stool color, as casein does not have a yellow pigment.

Arriving at the Correct Answer

Conclude that the yellow color of an infant's stool is due to the presence of bile pigments that are passed with the bile juice during digestion.

Key concepts

Understanding the Digestive Process

The human digestive process is a complex and fascinating journey that breaks down food into nutrients the body can absorb and use. Imagine your digestive system as a highly efficient processing plant, beginning in the mouth, where chewing and enzymes in saliva start the breakdown of food. As the food makes its way down to the stomach, more enzymes and acids continue the breakdown process in a highly acidic environment.

The journey doesn't end there—the partially digested food moves to the small intestine, where a cocktail of digestive juices from the liver, gallbladder, and pancreas play a pivotal role. Here, nutrients are absorbed into the bloodstream, and whatever remains, the non-absorbable parts, head towards the large intestine. This is where water is absorbed, and the leftover material is turned into stool, ready to be excreted. Certain components, like bile pigments, contribute to the stool's color, oftentimes providing that yellowish hue seen in infants.

The Role of Bilirubin

Bilirubin is a key player when it comes to understanding stool color. This yellow compound is a by-product of the normal breakdown of red blood cells in the body. The liver performs the critical function of processing bilirubin extracted from the bloodstream and then secreting it as bile.

Once in the digestive tract, bilirubin doesn't stay yellow. Through a chemical transformation journey, it changes from a yellow to a brownish-color (like that typical brown we associate with adult stool), which is usually the case once the stool has been exposed to the bacteria in the intestines.

Breaking Down Bilirubin

Enzymes in the intestine convert bilirubin into urobilinogen, and further degradation leads to a compound called stercobilin, which gives stool its brown color. In infants, however, the process isn't yet fully mature, leading to the lighter yellow-colored stools, particularly when breastfeeding, as seen in the initial exercise.

Liver Function in Digestion

The liver's function in digestion is both critical and multifaceted. It acts like a chemical processing plant, performing over 500 different functions, but regarding digestion, it processes nutrients, detoxifies harmful substances, and produces bile. Bile is essential—it's stored in the gallbladder and released into the small intestine to help digest fats and carry away waste, including those transformed bile pigments.

Processing and Detoxification

The liver is constantly at work. After we've absorbed nutrients from our digested food, the liver ensures these nutrients are safe for the body's use, remove toxins, and help balance our metabolism. Without the efficient work of the liver, including its role in the excretion of bilirubin, our digestive processes, and even overall health, could be compromised, exemplifying the necessity of proper liver function for healthy digestion and waste elimination.