If the surface barriers of innate immunity, such as the skin or mucous membranes are breached, the second line of defense in innate immunity is (are) the:

If the surface barriers of innate immunity, such as the skin or mucous membranes are breached, the second line of defense in innate immunity is (are) the:  lymphocytes

Explanation:

The lymphocytes direct and regulate immune responses. Specifically, B lymphocytes produce antibodies to fight against bacteria, viruses and invading toxins. T lymphocytes destroy the body's own cells that have been infected by viruses or that are cancerous.

unicellular organisms, like bacteria, are able to perform all life functions within one single cell. multicellular organisms need many different types of cells to carry out the same life processes. each of these special types of cells has a different structure that it perform a specific function.