Answer to Question 1
A vitamin A deficiency causes a decline in the integrity of the skin, lessoning its ability to serve as a barrier to pathogenic, disease-causing microbes. Vitamin A deficiency can also impair the membranes that protect the body's passages from infectious pathogens. Vitamin A helps cells, including the antibody-producing cells as well as the T lymphocytes and phagocytes, to develop normally and function fully.
Table 11-3 describes the impact of protein-energy malnutrition on the body's defenses. The immune system needs an adequate amount of protein to produce antibodies and white blood cells to protect the body against pathogens that cause infectious diseases. Proteins are not stored in the body and must be supplied by the diet each day.
Answer to Question 2
b