What type of membranes do not open to the exterior, do not contain glands, but do secrete fluid?

Question

Quizplus · Accepted Answer

Serous membranes do not open to the exterior, do not contain glands, but do secrete fluid. They line body cavities and cover organs, and secrete a watery fluid that helps reduce friction and lubricate the movement of organs against one another. Mucous membranes contain glands and open to the exterior, synovial membranes line joints, and secrete synovial fluid, goblet cells are a type of cell found in mucous membranes that produce mucus, and cutaneous membranes are the skin and do not secrete fluid.

What Type of Membranes Do Not Open to the Exterior