Membranes

What is Human Membrane?

A membrane is a sheet of tissue which covers or lines a surface, or divides an organ into lobes. There are two types of membrane, epithelial and fibrous. Epithelial membranes include mucous membranes and serous membrane.

Mucous membranes consist of epithelial tissue with underlying connective tissue called the lamina propria. These membranes are wet and slippery, and are found lining the various tracts of the body which open on to the body surface.

Serous membranes are thin, transparent membranes that line closed cavities of the body. They consist of two walls, the parietal layer and the visceral layer, with a potential cavity between the walls which contains some fluid. Each wall consists of a thin layer of either loose connective tissue or fibro-elastic tissue, covered with a layer of mesothelium (a kind of epithelium). Nerves, blood and lymph vessels are abundant in serous membranes.

Fibrous membranes are composed of connective tissue only. The superficial fascia (subcutaneous tissue), for example, is a combination of loose connective tissue and adipose tissue. It forms a continuous sheet under the skin to deeper tissues. Periosteum is composed of an outer layer of dense connective tissue containing many blood vessels and a deeper layer adjacent to the bone which it surrounds composed of loose connective tissue containing bundles of collagenous fibers and a network of thin elastic fibers.