why does blood turn dark red when dead or old?

Question

Im writing a fictional book and would like to explain in medical terms why the blood is dark and syrup like.

Answer 1

Firstly, there is a wide variation in the exact hue of blood from person to person. But, oxygenated blood is brighter in colour than deoxygenated. When blood is old, the haemoglobin gives up it's oxygen as the red cells die. So it goes darker.
The blood goes syrupy because the blood clots. When in the blood vessels, coagulation is prevented by a number of factors within the blood itself and from the vessel wall. When exposed to the air, and not inhibited from doing so, the blood begins to coagulate. Various proteins are crosslinked and joined together, increasing the viscosity of the fluid. This makes the blood go syrupy.

Answer 2

Blood, hemoglobin changes color dependent on it's oxygen content. Oxygenated blood fresh from the lungs is light red. Oxygen poor blood just before it enters the lungs is dark red.

The other factor is clotting, coagulation. This is a complex set up steps which slows the flow of blood and eventually thickens the blood.

Answer 3

because... when dead or old.. there is not too much oxygen in the body to supply the blood with oxygen.. so it turns dark red since some of the Hemoglobin, White blood cells and platelets would die

Answer 4

dark or brown blood is just not oxygenised enough and need getting air from the alviolies and diffused in to plasma in the blood cell which will got to the blood

Answer 5

It turns brownish because hemoglobin can't survive outside the body for that long, hemoglobin keeps oxygen in the blood to sevice the body.

Answer 6

okay, first of all, it's the lack of oxygen: oxyhemoglobin is lighter in color, carboxyhemoglobin is darker in color, so if the blood is not well oxygenated you have more carboxyhemoglobin. and an old person's hear and lungs do not function all that well and not that much oxygen is put into the system...
and when dead, the blood coagulates and particles separate, heavyer particles, which are darker in color end up clotting

Answer 7

DARK RED BLOOD MEANS IT'S DEOXYGENATED BLOOD THIS USUALLY IS RUNNING THROUGH THE MAIN VEIN THE VENA CAVA THAT RETURNS TO THE HEART ONCE IT'S SUPPLIED ENOUGH OXYGEN AROUND THE BODY! EVEN WHEN UR ALIVE

Answer 8

Because the oxygen is leaving the blood.

Answer 9

It is because of coagulation. The corpuscles get entangled in the mesh(fibrin) of the clot and its fluid part called serum separates out. Since the corpuscles become dead, they lose their physical and chemical properties in cluding colour etc.

Answer 10

Because that is what CSI tells us happens. But really, it is the lack of fresh oxygen, plus time, so you bleed red but clean up dark red dried blood. Pretty simple.