gastrointestinal « Back to Glossary IndexReferring to the digestive tract. Related Articles: 14 – 3 Microbes face many challenges when associating with a host14 – 8 The human microbiome15 – 4 The Immune System Is a Complex Collection of Organs, Tissues, and Cells15 – 5 The Innate Immune System17 – 2 The beginnings of disease and efforts to combat them« Back to Glossary Index