Blood flows in the arteries and veins of the body, 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 physicochemical qualities. And if you understand what color venous blood is and what 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 that fact that can be checked with the naked eye or measured using equipment. And it is possible to determine what color venous blood is, and what arterial blood, with your eyes or after spectral analysis. Venous is characterized by the presence of carboxyhemoglobin, which is why it acquires a cherry color. Arterial blood is scarlet due to the prevalence of oxyhemoglobin.
It is noteworthy that carbohemoglobin, which is found in the blood during carbon monoxide poisoning, also has a bright scarlet color. Their concentration can be measured using spectral photometry, which will accurately determine which venous blood and which arterial blood. Also, based on the color, this method allows you to calculate the concentration of blood gases and their partial pressure.
Blood gas composition
Just understanding what color venous blood is is not enough to understand its differences with arterial. To do this, you should study biochemical indicators, especially considering how many misconceptions regarding their differences are described in the materials on the Internet. The partial pressure of oxygen in venous blood is almost 40 mmHg, which is more than two times lower than in arterial (96 mmHg). The difference in carbon dioxide in connection with hemoglobin is approximately 14%: in the venous 46 mmHg, and in the arterial - 39 mmHg.
This means that hemoglobin in the veins is 50% saturated with oxygen, and the proportion of carbon dioxide is not 100%. This also means that carbon dioxide is also present in arterial blood. Its scarlet color is provided by the reflection spectrum of oxyhemoglobin, which is 2 times more here than in the veins, and 3 times more than carboxyhemoglobin. In venous blood, the proportion of carbon dioxide is only 12% greater than oxygen, although even such a difference provides its cherry color with a dark blue hue.
Biochemical blood differences
As well as the measurement of the partial pressure of gases, biochemical indicators give an expressed in figures idea of how venous blood differs from arterial blood. And first, it should be clarified that the veins collect it from a large circle of blood circulation, including from the intestines. That is, the absorption of nutrients occurs in the veins, which is why the concentration of fatty acids, chylomicron, low-density lipoproteins and glucose in them is 13-25% higher than in arteries. Moreover, the fat content decreases after the passage of the lungs, where about 15% of their mass is removed 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 the passage of the lungs, they are sent to the kidneys, where they are filtered into primary urine. This feature of detoxification and excretion does not allow us to state that veins contain more toxins than arteries. This is a common illiterate misinformation, since blood in the veins is “not dirtier” than arterial. 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 because of carbon dioxide, which gives protons and acidifies the medium 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. Differences in the amount of toxins and metabolites can be observed at different levels of the venous bed: before entering the hepatic pool or after renal filtration. But at the systemic level, their biochemical differences are minimal.
Bleeding
It is necessary to determine the type of blood by its appearance for the primary differentiation of bleeding. The volume of blood loss and, accordingly, the development of symptoms of hemorrhagic shock depend on the speed of its correct determination. The correct assessment of the type of bleeding allows you to quickly take the necessary measures to stop it, saving the life of the victim.
Signs of venous bleeding include slow uniform flow of dark red (cherry) blood from a wound, sometimes with minimal pulsation, but without a fountain. Arterial bleeding is the rhythmic ejection of a scarlet blood stream from a wound. Damage to the vein with the flow of blood is less dangerous, since the volume of blood loss increases slowly. Therefore, knowing what color venous blood is, you can quickly plan for assistance.
Hemorrhagic shock with 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 great 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 finger 15 cm above the wound.
Mixed bleeding
Often there are wounds in which there are signs of venous bleeding and arterial. Then a pulsating rich red scarlet stream is simultaneously ejected from one damage and venous blood of a cherry color flows evenly. Such an injury requires first stopping the arterial bleeding by applying a tourniquet or pressing the artery to the bone 15 cm above the damage, and then the venous one by applying a pressure bandage to the wound itself.