Blood vessels include a network of arteries, arterioles, capillaries, venules, and veins, carrying blood cells, water and chemicals throughout the body and can be referred to as organs. They are made from extracellular matrix proteins which form their basic structure. Haemoglobin (or Hemoglobin) in red blood cells is made up of two parts; haem/heme, which is an iron-containing compound responsible for oxygen binding in the lungs and globin, an iron-rich protein that carries oxygen throughout the body.
Dinosaur soft tissue blood clots discovered from three geological periods. How are they preserved? Images provided courtesy of Mark Armitage
A crucial question here is whether these dino circulatory components are found intact enough to represent the relatively short half-lives they are thought to have. One theory suggests components may have degraded to the point that their structures had become ‘unbound’ then rebinding into more stable matrices.
There are now more than 120 papers in peer-reviewed journal articles reporting soft tissues in dinosaur and other deep-time organic remains. These scientific papers describe biological material, including tissue and DNA, remaining inside fossils. A full list, which is being continually updated, is provided here: *List of Biomaterial Fossil Papers
Example papers for this topic:
(25) Heme in Tyrannosaurus rex bone 1997
(112) T. rex cortical bone blood vessel structures 2019
*This list of biomaterial papers can provide useful information for research and posting on topics within the Dinosaur Project Community. Thanks to researchgate.net for making this list freely available.