Final answer:
The two major classes of body membranes are cutaneous and serous membranes. The cutaneous membrane is the skin, while the serous membranes line body cavities that are closed to the exterior of the body.
Step-by-step explanation:
The two major classes of body membranes are a. cutaneous and serous. The cutaneous membrane refers to the skin, which is the largest organ of the body and protects the internal organs from the external environment. The serous membranes line body cavities that are closed to the exterior of the body, such as the peritoneal, pleural, and pericardial cavities.