Membranes
Membranes are thin, flat, flexible sheets of tissue that line body surfaces. There are 2 main categories of membranes, each containing epithelial and/or connective tissues.
A. Epithelial Membranes
Epithelial membranes are composed of thin layers of epithelial and connective tissue.
i) Mucous membranes Mucous membranes line cavities that open to the exterior. These include the digestive, respiratory, urinary and reproductive tracts. They consist of a lining layer of epithelium and an underlying layer of connective tissue. The lining layer is important for the body’s defense as microbes and other pathogens cannot easily penetrate it. Tight junctions connect the cells, and goblet cells secrete mucus to keep the cavities from drying out and to trap particles. In addition, the lining secretes some of the digestive enzymes needed to aid the digestion process. The CT portion is Areolar CT called Lamina Propria. It functions as support and binds to the underlying structures. It also holds blood vessels in place.
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