MODULE SUPPLEMENT: IMMUNE SYSTEM
The Physical Barriers

The physical barriers include the skin and mucous membranes. In another module the changes that occur with age in the skin will be discussed. However, these changes alter this barrier and include thinning, which increases the vulnerability to tearing/trauma, and less vascularity. Decreased vascularity inhibits the clearing of substances to which we are exposed.

The skin also has other more specific immune functions. Langerhan cells, which are immunocompetent cells, are involved in recognizing and processing foreign substances. These decrease with age, altering immune function (Gilchrest, 1999).

Mucous membranes, covering our eyes, alimentary canal, and genito-urinary tracts, play a protective role through providing a barrier and differential absorption. The mucosa of the GI tract is increasingly of interest (Hall, 1999) given lymphocyte production of IgA and other immunologically active substances that will be discussed. Alterations in this component of the immune system may predispose older adults to infections.