Collagen is an important protein that can be found throughout your body. In fact, it is found in all the connective tissues in your body ranging from your skin and bones, all the way down to your organs and blood vessels. Collagen functions several different ways in your body.
Upper gastrointestinal bleeding. Upper gastrointestinal bleeding (sometimes upper GI, UGI bleed, Upper gastrointestinal hemorrhage, gastrorrhagia) is gastrointestinal bleeding in the upper gastrointestinal tract, commonly defined as bleeding arising from the esophagus, stomach, or duodenum. Blood may be observed in vomit (hematemesis) or in altered form in the stool (melena).
Bilirubin (formerly referred to as haematoidin) is a yellow compound that occurs in the normal catabolic pathway that breaks down heme in vertebrates. This catabolism is a necessary process in the body's clearance of waste products that arise from the destruction of aged red blood cells.