Final answer:
The small intestine is situated in the abdominopelvic cavity, which is part of the anterior cavity of the human body and is found beneath the thoracic cavity, separated by the diaphragm.
Step-by-step explanation:
The small intestine is located in the abdominopelvic cavity. The anterior (ventral) cavity of the human body has two main subdivisions: the thoracic cavity, which is superior and encloses the lungs and heart, and the abdominopelvic cavity. This latter cavity is divided into two parts, the abdominal cavity where the digestive organs including the small intestine are found, and the pelvic cavity that houses the reproductive organs. The abdominopelvic cavity is separated from the thoracic cavity by the diaphragm.