Intestinal macrophages are critical in maintaining gut homeostasis. The small intestine develops from the midgut of the primitive gut tube. Altering diet may lead to changes in gut microbiota composition and diversity. Antibiotic usage reduces the diversity of gut microbiota. Abnormal proliferation of the candida in the gut may lead to dysbiosis. The change in gut flora causes no ill effects. The spleen is unique in respect to its development within the gut. Pharmacomicrobiomics is concerned with the interaction between drugs and the gut microbiome. This leads to inflammation of the gut and disease symptoms of IBD. The gallbladder develops from an endodermal outpouching of the embryonic gut tube. Hedgehog also participates in the coordination of eye, brain, gonad, gut and tracheal development. Dermatitis herpetiformis may be characterised based on inflammation in the skin and gut. Platelets in the veins draining the gut collect excess serotonin. There is very delicate balance between physiological role of gut serotonin and its pathology. Malabsorption occurs because of the destruction of gut cells called enterocytes.