In the arteries and veins of the body, blood constantly flows, which carries nutrients and oxygen to its tissues. This is the most important body fluid, which, depending on the concentrations of the main components, changes its physical and chemical qualities. And if you figure out what color is venous blood and what is arterial blood, you can delve into the processes of gas exchange. However, the differences between these, at first glance, completely different liquids are minimal.
Color characteristics
There is no doubt about the fact that can be checked with the naked eye or measured with equipment. And to determine what color is venous blood, and what is arterial, you can use your eyes or after conducting a spectral analysis. Venous is distinguished by the presence of carboxyhemoglobin, which is why it acquires a cherry color. Arterialscarlet blood due to the predominance of oxyhemoglobin.
It is noteworthy that carbohemoglobin, which is found in the blood during carbon monoxide poisoning, also has a bright scarlet color. Their concentrations can be measured using spectral photometry, which will accurately determine which blood is venous and which is arterial. Also, based on the color, this method allows you to calculate the concentration of blood gases and indicators of their partial pressure.
Blood gases
Just understanding what color venous blood is is not enough to understand its differences from arterial blood. To do this, you should study biochemical indicators, especially considering how many misconceptions about their differences are described in materials on the Internet. In venous blood, the partial pressure of oxygen is almost 40 mmHg, which is more than two times lower than in arterial blood (96 mmHg). For carbon dioxide in connection with hemoglobin, the difference is approximately 14%: in the venous 46 mmHg, and in the arterial - 39 mmHg.
This means that in the veins hemoglobin is saturated with oxygen by 50%, and the proportion of carbon dioxide is not 100%. This also means that carbon dioxide is also present in the arterial blood. Its scarlet color is provided by the reflection spectrum of oxyhemoglobin, which is 2 times more here than in veins, and 3 times more than carboxyhemoglobin. In venous blood, the proportion of carbon dioxide is only 12% more than oxygen, although even this difference ensures its cherry color with a dark blue tint.
Biochemicalblood differences
As well as measuring the partial pressure of gases, biochemical parameters give a numerical idea of how venous blood differs from arterial blood. And first it should be explained that the veins collect it from the systemic circulation, including from the intestines. That is, the absorption of nutrients occurs in the veins, which is why the concentration of fatty acids, chylomicrons, low-density lipoproteins and glucose in them is 13-25% higher than in the arteries. Moreover, the content of fats decreases after passing through the lungs, where about 15% of their mass is withdrawn from the bloodstream for the synthesis of surfactant.
Through the veins, blood is removed from tissues that secrete their metabolites. They reach the liver, where they are eliminated from the bloodstream. Or after passing through the lungs, they are sent to the kidneys, where they are filtered into the primary urine. This feature of detoxification and excretion does not allow us to argue that the content of toxins in the veins is greater than in the arteries. This is a common illiterate misinformation, since the blood in the veins is “not dirtier” than the arterial one. It only has a slightly lower pH (7.35 instead of 7.4 for arterial), that is, it is less alkaline than arterial blood.
This is not observed due to metabolites, but due to carbon dioxide, which gives protons and acidifies the environment by 0.05 pH. Because, with the exception of the carbonate buffer capacity and the concentration of carbon dioxide, venous blood is identical to arterial blood. Differences in the amount of toxins and metabolites can be observed at different levelsvenous bed: before flowing into the hepatic pool or after renal filtration. But at the system level, their biochemical differences are minimal.
Bleeding
Determining the type of blood by its appearance is necessary for the primary differentiation of bleeding. The volume of blood loss and, accordingly, the development of symptoms of hemorrhagic shock depends on the speed of its correct determination. A correct assessment of the type of bleeding allows you to quickly take the necessary measures to stop it, saving the victim's life.
Signs of venous bleeding include a slow uniform outflow of dark red (cherry) blood from the wound, sometimes with minimal pulsation, but without the presence of a fountain. Arterial bleeding is the rhythmic ejection of a jet of scarlet blood from a wound. Damage to a vein with blood leakage is less dangerous, since the volume of blood loss increases slowly. Therefore, knowing what color venous blood is, you can quickly plan your care.
Hemorrhagic shock in case of damage to the veins occurs much later, which is easier to prevent by applying a pressure bandage to the wound area. Arterial bleeding is extremely dangerous due to the large blood loss and the rapid development of hemorrhagic shock. It requires a quick reaction - a temporary stop of bleeding by squeezing the artery with a tourniquet or a finger 15 cm above the wound.
Mixed bleeding
Wounds often show signs of both venous bleeding and arterial bleeding. Then from one damageat the same time, a pulsating saturated red scarlet jet is ejected and cherry-colored venous blood flows out evenly. Such an injury requires first stopping arterial bleeding by applying a tourniquet or pressing the artery to the bone 15 cm above the injury, and then venous bleeding by applying a pressure bandage to the wound itself.
