The ________ is the site of the complete digestion of carbohydrates, proteins and fats.

The correct answer is small intestine.Key Points

• The small intestine is the site of the complete digestion of carbohydrates, proteins and fats because it is the longest part of the digestive system and has specialized structures called villi and microvilli that increase its surface area for absorption.
• Carbohydrates are broken down into simple sugars like glucose, proteins are broken down into amino acids, and fats are broken down into fatty acids and glycerol in the small intestine.

Additional Information

• The small intestine is divided into three parts: duodenum, jejunum and ileum, with the duodenum being the first and shortest segment that receives digestive enzymes from the pancreas and bile from the liver.
• The liver is the largest gland in the body and performs many important functions, including detoxifying harmful substances, storing vitamins and minerals, and producing blood-clotting proteins.
• The large intestine is about 1.5 meters long and has four main regions: cecum, colon, rectum and anal canal, with the colon being the longest part that is further divided into ascending, transverse, descending and sigmoid segments.
• The food pipe is a muscular tube that is about 25 centimeters long and has two sphincters, one at the upper end near the throat and one at the lower end near the stomach, that prevent food and stomach acid from flowing back.