Mucous Membranes
Mucous Membranes
Mucous membranes play a key role in sexual activities. These membranes line body canals that open to the outside environment, including the mouth, lips, nose, the inside of the eyelids, the lungs and windpipe, the digestive tract, the vagina, the inside of the vulva, the glans and foreskin of the penis, the urethra, and the rectum. Mucous membranes are comprised of epithelial tissue, or the cells that layer to form a protective covering. Skin has several layers of epithelial cells. Mucous membranes are made up of three layers of tissue: a layer of epithelial cells, which also contains blood vessels, lymph vessels, and goblet cells that secret mucus; a layer of lamina, or connective tissue; and a layer of muscle cells. The presence of blood vessels makes mucous membranes pink in color. Some mucous membranes also contain pigments that hide the blood vessels.
Mucous membranes protect the surfaces of the canals and organs they cover. The mucus secreted by the goblet cells is a thick fluid that shields surfaces and organs, lubricates passages, traps foreign particles, and absorbs water-soluble substances such as salts. Not all mucous membranes secrete mucus—the name of the membrane refers to where the membranes are located rather than to their secretion of mucus.
The color of mucous membranes, especially in the eyelid, reflects the number of red blood cells flowing through membrane blood vessels. For this reason, the mucous membranes of the eyelid provide some indication of relative health. If the mucous membranes are pale, this indicates a decreased number of red blood cells, which may indicate a number of problems such as shock, bleeding, or poisoning. Yellow membranes indicate jaundice, which may be caused by liver diseases such as hepatitis.
Not only are mucous membranes sensitive to the touch, they respond to touch and other stimuli by producing mucus. In addition, sexual stimulation in other regions such as the lips and nipples increases the flow of mucus in areas such as the genitals, which are lined with mucous membranes. Increased mucus makes touching more pleasurable by providing a layer of protection against irritation and making passage over surfaces easier. Males who have been circumcised have had a portion of this mucous membrane removed and may experience more irritation in the less protected glans. Increased mucus in the vulva and vagina not only indicates sexual arousal, but also facilitates penetration and the movement of sperm. Postmenopausal women often experience a decrease in mucus secretions, which makes sexual intercourse more difficult and uncomfortable. Commercial lubricants can be used to substitute for the decrease in mucus. Because the mucous membranes are sensitive and absorb water-soluble chemicals with which they come into contact, it is necessary to choose such lubricants with care to avoid damaging the membranes.
BIBLIOGRAPHY
Marieb, Elaine N., and Katja Hoehn. 2006. Human Anatomy and Physiology. 7th edition. San Francisco: Pearson/Benjamin Cummings.
Marieb, Elaine N. 2006. Essentials of Human Anatomy and Physiology. 8th edition. San Francisco: Pearson/Benjamin Cummings.
Netter, Frank H. 2006. Atlas of Human Anatomy. 4th edition. New York: Saunders/Elsevier.
Judith Roof