Does blood have to be red? Why shouldn’t it, for example, be green or blue, or, in general, like in the movie “Predator,” glow in the dark? Do you remember the colorless blood-acid in Alien? Or the “blue blood” of Russian nobles? Isn't it cool? So, let's try to figure out what causes the color of blood:
All people have red blood. As you know, it gives color hemoglobin, which is the main component of the red blood cell, filling it by 1/3. It is formed as a result of the interaction of the globin protein with four iron atoms and a number of other elements. It is thanks to iron oxide (Fe 2+) that hemoglobin acquires red color. All vertebrates, some species of insects and mollusks have iron oxide in their blood protein, and therefore their blood has a scarlet color.
But it turns out that blood doesn’t have to be red at all. Some animals have blood of a completely different color. For example, in some invertebrates, oxygen is carried not by hemoglobin, but by another iron-containing protein - hemerythrin or chlorocruorin.
Hemerythrin, which is a respiratory pigment in the blood of brachiopods, contains five times more iron than hemoglobin. Oxygenated hemerythrin gives blood violet tint, and having given oxygen to the tissues, such blood becomes pink. Hemerythrin is localized in cells, which, unlike ordinary red blood cells, are called pink blood cells.
But in polychaete worms the respiratory pigment is another iron-containing protein - chlorocruorin, dissolved in blood plasma. Chlorocruorin is close to hemoglobin, but its basis is not oxide iron, but ferrous iron, which gives blood and tissue fluid green color.
However, nature is not limited to these options. It turns out that the transfer of oxygen and carbon dioxide can be carried out by respiratory pigments based on ions of other metals (besides iron).
For example, sea squirts have blood colorless, since it is based on - hemovanadium, containing vanadium ions.
Do you remember our nobles with blue blood? It turns out that this happens in nature, but the truth is only in octopuses, octopuses, spiders, crabs and scorpions. The reason for such a noble color lies in the fact that the respiratory pigment of their blood is not hemoglobin, but hemocyanin, in which copper (Cu 2+) is present instead of iron. Combining with atmospheric oxygen, hemocyanin turns blue, and, giving oxygen to tissues, it becomes somewhat discolored. As a result of this, these animals have blood flowing in their arteries. blue blood, and in the veins is blue. If hemoglobin is usually found both in plasma and in blood cells (most often in red blood cells), then hemocyanin is simply dissolved in blood plasma. Interestingly, there are organisms, for example, some mollusks, which can simultaneously contain hemoglobin and hemocyanin, and in some cases one of them acts as an oxygen carrier in the blood, and the other in the tissues.
By the way, there are still known cases when people had blue blood. True, not at all among the nobles. The Trud newspaper once published about one such case (dated March 17, 1992):
“Mikheev, a resident of Severodvinsk, decided to donate blood for noble reasons, as well as to receive a discounted lunch coupon. He passed. The doctors looked at it and gasped: the blood turned out to be a strange bluish color. They sent it for analysis to the Arkhangelsk Toxicology Laboratory. It turned out that unusual color caused by functional changes in the liver. And these changes are associated with Mikheev’s habit of drinking alcohol-containing liquids of ignoble, let’s say, origin. For example... stain..." Who knows, maybe our blue-blooded kings didn't disdain stain either... ;-)
Well, and finally, a tablet where all this completely useless knowledge about the color of blood is brought together:
Blood color |
Where is it contained? |
Main element |
Representatives |
|
Red, scarlet |
Hemoglobin |
Red blood cells, plasma |
All vertebrates, some invertebrate species |
|
Violet
|
Hemerythrin |
Pink blood cells |
Brachiopods, sipunculids, priapculids |
|
Green |
Chlorocruorin |
Polychaete worms (polychaetes) |
||
Colorless |
Hemovanadium |
Sea squirts |
||
Blue |
Hemocyanin |
Many molluscs and arthropods |
P.S. By the way, why did I get interested in this stupid question about the color of blood... The fact is that last week I had fun with the fact that, together with kpblca wrote a semi-fiction story. The beginning, but the unfinished “story” itself. By the way, maybe there will be people willing to write a sequel to it...
Update (14-Jun-2003): The story would be incomplete if, having talked about red, green, blue, blue and violet blood, I did not mention the yellow and orange blood, which is often found in insects.
The reason that I forgot about this blood is that I was looking for information about respiratory pigments, and in insects, the blood (or more precisely, the hemolymph) is devoid of these pigments and does not participate in the transfer of oxygen at all. Respiration in insects is carried out using tracheas - branching tubes that directly connect the cells of the internal organs with the air environment. The air inside the tracheal tube is motionless. There is no forced ventilation, and the influx of oxygen into the body (as well as the outflow of carbon dioxide) occurs due to diffusion due to the difference in the partial pressures of these gases at the inner and outer ends of the tube.
This oxygen supply mechanism strictly limits the length of the tracheal tube, the maximum length of which is quite simply calculated, so the maximum size of the body of the insect itself (in cross-section) cannot exceed the size chicken egg. However, if there were higher pressure on our planet, insects could reach gigantic size(like in science fiction horror films).
The color of hemolymph in insects can be almost any color, because... it contains many different substances, including poisons and acids. Thus, the blister family got its name precisely because of the ability of its representatives (for example, the Spanish fly) to secrete drops from the joints of the thighs and legs yellow blood, which when it comes into contact with human skin causes burns and abscess-like watery blisters.
The hemolymph of representatives of many families contains very toxic substances, in particular cantharidin. If such poisonous hemolymph enters the mouth, it can cause serious poisoning and even death. The blood of ladybugs is especially poisonous - it has a specific smell, is cloudy, yellow-orange the liquid that they secrete in case of danger.
Blood forms the basis of the life of a living organism. Circulating through the system of blood vessels, veins and arteries, it transports oxygen and substances necessary for metabolism or resulting from it to various organs. metabolic processes.
But transportation nutrients and metabolic products, blood functions are not limited. Blood regulates body temperature and transports hormones responsible for vital processes; protects the body from infections and damage.
What is blood for: basic functions
Almost all processes in the body related to respiration and digestion are associated with blood supply. It is the blood that transports oxygen from the lungs to the tissues, and carbon dioxide from the tissues and organs to the lungs. The secretion products of endocrine glands - hormones - are transported throughout the body with the blood, and this ensures coordination between various organs.
Nutrients from small intestine Through capillaries, thanks to the blood, they travel from the digestive tract to the liver. This is where the modification happens fatty acids, glucose, amino acids and regulation of their quantity, depending on what the body needs for this moment to a greater extent. 
Further, the transported substances reach their “destination points” through tissue capillaries. End products enter the blood from tissues, which are then excreted from the body, for example, in urine.
In warm-blooded organisms, blood plays a primary role in the process of maintaining optimal body temperature, or thermoregulation. In different parts of the body, the absorption and release of heat must be balanced, and this balance is made possible precisely because the blood carries heat.
The main center of thermoregulatory processes is located in the brain - the hypothalamus, which is sensitive to changes in the temperature of the blood passing through it. The hypothalamus regulates the processes by which heat is released or absorbed.
For example, heat loss can be regulated by changing the diameter of the skin's blood vessels, which in turn changes the volume of blood flowing near the surface of the body (which is where heat is lost most easily).
About the color of blood
Blood is a liquid, the fluidity of which is determined by its viscosity and the nature of the movement of its components. Blood viscosity depends on the number of red blood cells and proteins it contains, and affects the speed of blood movement and blood pressure.
Blood consists of pale yellow plasma, which contains three types of cellular elements: red blood cells (erythrocytes), white cells (leukocytes), and platelets (platelets). The total volume of blood in the body of an adult male is about five liters, with most of it being plasma and the rest mostly red blood cells. Red blood cells contain the pigment hemoglobin, which gives blood its red color.
The main function of red blood cells is to transport oxygen, and hemoglobin plays a key role in this process. Hemoglobin is an organic pigment that contains a compound of porphyrin with iron (heme) and the protein globin.
It is known that the blood in the arteries and veins has different shades: venous blood is dark, arterial blood is bright scarlet. This happens because the arteries carry blood from the heart and lungs and are saturated with oxygen. And through the veins, blood from tissues and organs flows to the heart, the hemoglobin in this blood is almost devoid of oxygen, which is why it has dark color.
Can blood be a different color?
Of course it can. For example, the blood of octopuses, scorpions, crayfish, spiders are blue, because instead of hemoglobin it contains hemocyanin, and in it the metal is not iron, but copper. 
If iron colors human blood red, copper gives the blood of octopuses and other organisms a blue or blue tint. By the way, when octopus blood is saturated with oxygen, it darkens, and in the veins, on the contrary, it turns pale.
And in nature there are sea worms whose blood is green. It gets this color thanks to the ferrous iron it contains.
If appeared fair blood If you have your period, but previously your menstruation was of a different nature (color, consistency, smell), you should immediately visit a gynecologist. Often such discharge is a sign serious illness. You may need to consult a neurologist and endocrinologist.
In the absence of deviations, the color of the secreted fluid may be scarlet, dark red or brown in the first and last days (daub). It also contains inclusions of mucus, fragments of rejected endometrium
Menstruation should be without the presence of an unpleasant (fetid) odor, itching, burning, severe pain, . This is considered normal if menstruation began on time, no less than 21 days from the previous critical days, the blood does not clot, overall volume discharge on average does not exceed 80-100 ml for the entire period, and their duration ranges from 3 to 7 days.
If women of reproductive age have periods like water with blood throughout the entire period, then at the end of it it will be necessary to seek advice from a gynecologist. It is recommended to be examined using an ultrasound (transvaginal), video colposcope (extensive colposcopy), and donate blood to determine the level of hemoglobin and hormones.
In girls for a year or 2 years after menarche and in women during premenopause, the preservation of scarlet (light) color of menstrual blood is not a pathology. However, a doctor's examination is recommended to rule out diseases.
Light, not abundant bleeding 2-2.5 weeks after menstruation may be due to ovulation (when the egg is released, the hormonal levels change, the follicle membrane is damaged). May be implantation bleeding, when the embryo implants into the endometrial tissue, rupturing the vessels. Normally, such red discharge lasts from several hours to 3-5 days, which is why women perceive it either as menstruation or as a deviation.
Pathology during light menstruation
There are several reasons why the discharge remains bright red, pink or faintly colored (beige), or critical days appear ahead of schedule. These are endocrine, gynecological and venereal diseases, spontaneous abortions early stage pregnancy, trauma to the mucous membranes with an intrauterine device, the consequence of unsuccessful curettage, cancer.
Symptoms of pathological abnormalities:
- less than 3 weeks or more than 35 days have passed between menstruation;
- scanty or heavy periods or they last longer than 7 days;
- there are clots larger than 2-2.5 cm;
- systematic cycle failures;
- light remains throughout the entire period of critical days;
- unpleasant odor reminiscent of rotten fish;
- itching, dryness;
- body temperature is higher than normal;
- cutting or other pain in the area genitourinary organs, paths;
- scanty discharge becomes more abundant over time, without signs of completion;
- bleeding systematically resumes every few days.
If there is at least one symptom, a diagnosis should be carried out immediately to find the cause of the deviation. Gynecological examination is required even if the color of menstruation is normal (dark red, not bright), but there are other symptoms of pathology. Early diagnosis will avoid complications, one of which is iron deficiency anemia. 
Reasons for the appearance of light-colored blood:
- criminal abortion;
- miscarriage;
- bacterial infections acquired through sexual contact (STDs);
- damage to the mucous membranes or endometrium by a medical instrument;
- incorrectly selected hormonal drugs, including contraception;
- low hemoglobin level.
With the help of a gynecologist, laboratory and hardware diagnostics, it is easier to identify the causes that provoked bleeding or eliminate factors that contribute to its reoccurrence. For example, they select adequate hormonal contraception, remove the intrauterine device, eliminate the consequences of abortion, and use other treatment methods.
Bacterial vaginosis
The vaginal microflora of women contains lactobacilli, which maintain optimal acidity of the reproductive tract environment and suppress pathogenic infections streptococcus, coli, staphylococcus and other agents. If they are violated natural level a woman may develop gardnerellosis (synonyms: dysbiosis of the vaginal environment, bacterial vaginosis).
Usually, the number of lactobacilli changes due to excessive douching, the use of low-quality products for intimate hygiene, after sexual intercourse (unprotected sex) or drug treatment (by-effect drugs). Pathology does not apply to venereology.
Symptoms of the disease: rotten fish (the aroma intensifies after sex), light blood, a lot of mucus, itching. For diagnosis, additional smears are taken from which pathogenic microflora will be inoculated.
If vaginosis is confirmed, therapy is prescribed using antibacterial drugs and other drugs appropriate for the treatment of the specific stage of the disease. It is necessary to eliminate gardnerellosis to avoid inflammatory processes.
During menstruation, the blood may appear pink, bright red, or like slightly colored water (ichor). If a test confirmation of pregnancy has already been received (standard or hCG), then such menstruation is a sign spontaneous abortion. A situation like this requires medical supervision with possible hormonal adjustments to preserve the fetus.
However, there are often cases when menstrual cycle operates according to schedule throughout the first trimester and is light. A doctor's consultation is advisable.
Conclusion
A woman is recommended to undergo regular general routine medical examinations to protect yourself from complications various diseases. After all, light menstrual blood occurs when there is a malfunction thyroid gland(hormonal imbalances), due to overwork, chronic fatigue, poor nutrition (strict diets), diseases nervous system and for many other reasons.
Blood performs many vital functions in our body. It is no coincidence that large blood loss, as well as poor circulation, can be disastrous for us. We suggest that you familiarize yourself with the list of functions that are “assigned” to blood:
- Transport function. Blood is “responsible” for transporting various substances. It is thanks to her that cells and internal organs receive oxygen and nutrients, the blood removes carbon dioxide and metabolic end products from them. In this regard, three subfunctions are distinguished: respiratory, trophic and excretory.
- Thermoregulatory function. Blood, in addition to oxygen and nutrients, transfers heat from more heated organs to less heated ones.
- Protective function. Implementation of non-specific and specific immunity: Blood clotting prevents blood loss during injury.
- Regulatory, or humoral function. This refers to the delivery of hormones, peptides, ions and other physiological active substances from the places of their synthesis to the cells of the body, which allows for the regulation of many physiological functions.
- Homeostatic function. Blood ensures the maintenance of constancy internal environment body (acid-base balance, water-electrolyte balance and other parameters).
Blood composition
The liquid component of blood can be distinguished - blood plasma and blood cells. Shaped elements- these are erythrocytes, leukocytes and platelets. The share of formed elements accounts for 40–45%, the share of plasma – 55–60% of blood volume.
Blood plasma
From 90 to 92% of blood plasma is water, and the remaining 8–10% is dry residue, which consists of organic and inorganic substances. Plasma constantly contains all vitamins, microelements, as well as intermediate metabolic products.
Formed elements of blood
Red blood cells. They contain hemoglobin, which makes our blood red. Perform the following functions:
- respiratory;
- regulation of blood pH;
- nutritious;
- protective;
- participate in the process of blood clotting;
- are carriers of various enzymes and vitamins (B1, B2, B6, ascorbic acid);
- are carriers of group blood characteristics.
Leukocytes. They are also white blood cells - colorless cells ranging in size from 8 to 20 microns. Perform in the body protective function. White blood cells are produced in red bone marrow from a single stem cell.
Platelets, or blood platelets - flat cells of irregular round shape with a diameter of 2–5 microns. The main function of platelets is to participate in hemostasis (stopping bleeding in case of damage to the walls of blood vessels and maintaining the liquid state of the blood). Platelets “produce” and secrete a number of biologically active substances: serotonin, adrenaline, norepinephrine and substances called lamellar coagulation factors.
Hemoglobin and red color of blood
As already mentioned, it is hemoglobin that colors our blood red. It is also the basis of the red blood cell, filling it by 1/3. It is formed as a result of the interaction of a protein called globin with four heme molecules.
Heme, which contains a divalent iron atom that can attach or donate an oxygen molecule. In this case, the valence of iron, to which oxygen is attached, does not change.
It is thanks to this divalent iron oxide (Fe2+) that hemoglobin acquires its red color. All vertebrates, some species of insects and mollusks have iron oxide in their blood protein, and therefore their blood is red.
Blood of a different color
Red is not the only blood color possible in nature. And this is due to the fact that some living beings’ red blood cells contain not hemoglobin, but other iron-containing proteins. This is observed in some species of invertebrates, in particular mollusks.
Their blood contains the protein hemerythrin, which is a respiratory pigment in the blood and contains five times more iron than hemoglobin. Hemerythrin, saturated with oxygen, gives the blood a purple tint, and when it gives oxygen to the tissues, such blood becomes pink.
Another iron-containing protein - chlorocruorin - gives blood and tissue fluid green color. This protein is dissolved in the blood plasma and is close in composition to hemoglobin, but the iron in it is not oxide, as in the blood of mammals, but ferrous. That's why the color turns out green.
However, the color range of the blood of living beings is not limited to red, purple and green. For example, octopuses, octopuses, spiders, crabs and scorpions are blue bloods in the most literal sense. The reason is that in these animals and insects the respiratory pigment of the blood is not hemoglobin, but hemocyanin, which contains copper (Cu2+) instead of iron.
By the way, recently, as a result of one of the studies, a discovery was made regarding the ancient Egyptians, more precisely, the color of their blood: it is quite possible that they also had blue.
Science knows that different living organisms on the planet have different blood colors.
However, in humans it is red. Why is blood red? This question is asked by both children and adults.
The answer is quite simple: the red color is due to hemoglobin, which contains iron atoms in its structure.
What makes blood red is hemoglobin, which consists of:
- From a protein called globin;
- The non-protein element heme, which contains the ferrous ion.
It was possible to find out what gives the red color, but its elements turn out to be no less interesting. What elements give it this color is an equally interesting aspect.
Blood contains:
- Plasma. The liquid is light yellow in color, with its help the cells in its composition can move. It is composed of 90 percent water, with the remaining 10 percent made up of organic and inorganic components. Plasma also contains vitamins and microelements. The light yellow liquid contains many useful substances.
- The formed elements are blood cells. There are three types of cells: white blood cells, platelets and red blood cells. Each type of cell has certain functions and characteristics.
These are white cells that protect the human body. They protect him from internal diseases and foreign microorganisms penetrating from outside.
This is a white element in color. Its white hue is impossible not to notice during laboratory research, so such cells are determined quite simply.
White blood cells recognize foreign cells that can cause harm and destroy them.
These are very small colored plates whose main function- folding.
These cells are responsible for ensuring that the blood:
- It coagulated and did not flow out of the body;
- Coagulates quite quickly on the surface of the wound.
More than 90 percent of these cells are in the blood. It is also red because red blood cells have this hue.
They carry oxygen from the lungs to peripheral tissues and are continuously produced in the bone marrow. They live for about four months, then are destroyed in the liver and spleen.
It is very important for red blood cells to carry oxygen to various tissues of the human body.
Few people know that immature red blood cells are blue, then acquire a gray tint and only then become red.
There are quite a lot of human red blood cells, which is why oxygen reaches peripheral tissues so quickly.
It is difficult to say which element is more significant. Each of them has important function affecting human health.
Children often ask questions regarding the components of the human body. Blood is one of the most popular topics of discussion.
Explanations for children should be extremely simple, but at the same time informative. Blood contains many substances that differ in function.
Consists of plasma and special cells:
- Plasma is a liquid that contains useful substances. It has a light yellow tint.
- The formed elements are erythrocytes, leukocytes and platelets.
The presence of red cells - erythrocytes - explains its color. Red blood cells are red by nature, and their accumulation leads to the fact that a person’s blood is exactly this color.
There are about thirty-five billion red cells that move throughout the human body in the blood vessels.
Why are veins blue
The veins carry burgundy blood. They are red, like the color of the blood that flows through them, but not blue. The veins only appear blue.
This can be explained by the law of physics about the reflection of light and perception:
When a ray of light hits the body, the skin reflects some of the waves and looks light. However, it transmits the blue spectrum much worse.
The blood itself absorbs light of all wavelengths. Skin gives for visibility Blue colour, and the vein is red.
Human brain compares color blood vessel against warm skin tone, resulting in blue.
Blood of a different color in various living creatures
Not all living organisms have red blood.
The protein that gives this color in humans is hemoglobin, contained in hemoglobin. Other living beings have other fat-containing proteins instead of hemoglobin.
The most common shades besides red are:
- Blue. Crustaceans, spiders, mollusks, octopuses and squids boast this color. And blue blood has great value for these creatures, as it is filled important elements. Instead of hemoglobin, it contains hemocyanin, which contains copper.
- Violet. This color is found in marine invertebrates and some mollusks. Typically, such blood is not only purple, but also slightly pink. Color pink blood in young invertebrate organisms. IN in this case protein - hemerythrin.
- Green. Found in annelids and leeches. The protein is chlorocruorin, close to hemoglobin. However, iron in this case is not oxide, but ferrous.
The color of blood varies depending on the protein it contains. Whatever color the blood is, it has a huge amount useful substances necessary for a living organism. Pigment is important for every organism, despite its diversity.
Video - Secrets and mysteries of our blood
