Final answer:
The small intestine is the key part of the digestive tract for chemical digestion and nutrient absorption, consisting of the duodenum where digestion begins, and the jejunum where most nutrient absorption occurs.
Step-by-step explanation:
The part of the digestive tract that plays the primary role in chemical digestion and nutrient absorption is the small intestine. The small intestine is a long, tube-like organ that begins at the stomach and ends at the large intestine. Its inner surface is covered with tiny projections known as villi and microvilli, which greatly increase its surface area, aiding in the efficient absorption of nutrients into the blood.
The small intestine is divided into three segments: the duodenum, jejunum, and ileum. The duodenum is the first part where most chemical digestion occurs, with many enzymes and chemicals being secreted here. The jejunum is the second part and the primary site where the hydrolysis of nutrients continues, and most of the carbohydrates and amino acids are absorbed. Lastly, the ileum is involved in the absorption of bile salts and vitamins. Overall, the small intestine's intricate structure with villi contributes to its enormous surface area comparable to the size of a basketball court, making it remarkably efficient for absorption.