Final answer:
The essential functions of the body cavity of the trunk, specifically the ventral cavity, include the protection and support of vital organs.
Step-by-step explanation:
The essential functions of the body cavity of the trunk, specifically the ventral cavity, include the protection and support of vital organs such as the lungs, heart, stomach, intestines, and reproductive organs. Additionally, the ventral cavity allows for changes in the size and shape of these organs as they perform their functions.