Blood Function and Composition in the Human Body

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Some people may have phobias or fear of blood. But do you really know what is blood function and what they doing in human body?

Actually blood is one of the most important parts of our body. So important that if humans and animals lack blood, either because of injury or because of certain diseases, the body will become weak and then die.

Blood is a combination of plasma (fluid) and cells floating in it. Blood is a special fluid in the body that provides essential substances and nutrients, such as sugar, oxygen and hormones, for the body’s cells.

In addition, blood also brings waste out of these cells. The wastes are then discharged through urine, feces, sweat and breath (in the form of carbon dioxide).

Blood is a fluid in the body that consists of blood plasma, red and white blood cells that circulate in human or animal blood vessels.

Most of the composition of blood consists of red blood cells which have a function to transport oxygen throughout the body which is needed by humans. So that blood becomes one of the vital components in the body.

Then what happens if someone lacks blood? The person’s body will be weak because they do not have enough oxygen to be used to produce energy. If this is left unchecked, the worst possible cause can cause death.

Blood Composition

Normally, 7-8% of the weight of the human body comes from blood. In adults, there are 4-5 liters of blood. This important liquid has an important function in circulating oxygen and nutrients to all cells and removing carbon dioxide, ammonia and other waste products. In addition, blood plays a vital role in the immune system and keeps the body temperature constant.

Blood is a very special network made from more than 4000 different components. Four of these important components are red blood cells, white blood cells, platelets and plasma.

All humans produce these blood components, without exception.

Red Blood Cells

Red blood cells, also known as erythrocytes, are shaped like flat plates and slightly curved in the middle. This is the most abundant blood cell in the body. Approximately 40-50% of all blood volume is red blood cells.

Red blood cells contain hemoglobin (Hb or Hgb). Hemoglobin is a type of protein that contains iron, and serves to deliver oxygen from the lungs to all tissues and cells of the body. The protein fills 97% of the dry substance of red blood cells.

Every red blood cell has a life span of about four months. After that, the cells are removed by the spleen and Kupffer cells in the liver. Therefore, to meet their needs, the body continues to replace the dead red blood cells.

Functions of Red Blood Cells

The main job of red blood cells is to carry oxygen and circulate it throughout the body. If there are enough red blood cells, the oxygen needed by the body will be fulfilled. Conversely, if the number of red blood cells decreases, this can cause health problems, such as anemia.

White Blood Cell

White blood cells or leukocytes are part of the human immune system. This means
white blood cells are in charge of defending the body from infection and foreign material
from outside the body. Normally, there are about 4 x 1010 white blood cells in one liter of blood or about 1% of the total blood count of a healthy person.

Two types of white blood cells namely, lymphocytes and ganulocytes, move freely in the body. If on both trips ‘meet’ with bacteria, viruses, or germs, these cells will immediately work to attack the foreign material.

In addition, lymphocytes and ganulocytes can enter and exit the bloodstream and reach infected tissues or parts. White blood cells also work against abnormal cells, such as cancer cells.

Functions Of White Blood Cells

White blood cells function as antibiotics that will fight diseases that attack the body, white blood cells are usually used to maintain immunity, if a person is deficient in white blood cells it is not impossible that someone will easily feel tired, fatigued and lethargic because the immune system is not balanced.


Trombocyte, also known as platelets, play a role in the process of blood clotting (coagulation). If our body is injured and bleeding, platelets gather to form clots.

If exposed to air, platelets break down and release fibrinogen into the bloodstream. This triggers a series of reactions that produce blood clots. Soon the dried crust (sores) began to form.
Platelets have the most different forms than other blood component forms. The shape of the blood platter is irregular, even changing. Besides that the blood chips have the same color.

In the body of a healthy person, there are approximately 250,000 platelets in every cubic millimeter of blood.

The Function of Platelets

The role of platelets is to block damaged blood vessels to prevent blood loss. Under normal conditions, platelets move through the blood vessels in an inactive state. Inactive platelets have a distinctive shape like a plate. When in a blood vessel, platelets become active by the presence of certain molecules in the blood.

These molecules are secreted by vascular endothelial cells. Active platelets change shape and become more rounded elongated, like fingers stretching from cells.

They also become sticky and follow each other on the surface of blood vessels to repair damaged blood vessels.
Platelets actively release chemicals that cause blood protein fibrinogen to be converted to fibrin. Fibrin is a structural protein that is arranged into long, fibrous chains.

When fibrin molecules converge, they form long, fibrous and sticky nets that trap platelets, red blood cells, and white blood cells. Platelet activation and the blood clotting process work together to form clots.

Platelets also release signals that help to call more platelets to sites damage to blood vessels, and activate additional clotting factors in blood plasma

Blood Plasma

Blood plasma has a clear, clear and slightly yellowish color. Normally, 55% of the blood volume in the body is plasma. When the heart pumps blood throughout the body, blood plasma also carries nutrients to the cell. At the same time, plasma also secretes metabolic waste.
In blood plasma there is also a mineral salt content that works to regulate blood pH and also osmotic in the blood. Other ingredients carried by blood plasma include blood clotting factors, glucose, fat, vitamins, minerals, hormones, enzymes, antibodies, and other proteins.

These proteins function to regulate blood pressure, and also fight attacks of diseases such as white blood cells.

Functions of Blood Plasma

Naturally blood is not obtained from outside the body. The body forms its own blood components in the form of red blood cells, white blood cells, platelets, and blood plasma.

On average, each person has a blood content of 4-6 liters in his body, depending on body weight and age.

Although not so well known by the general public, blood plasma has an important role for the body. Protein in the blood plasma functions to help the blood clotting process and transport important substances through the blood throughout the body.

Blood plasma itself contains nutrients that dissolve in it, including blood sugar or glucose.

Blood plasma also contains salt and enzymes.

Then blood plasma is also in charge of helping the body’s cells get rid of the waste that is in the body. Body cells carry waste, then store it in the blood plasma. After that, the blood plasma removes the waste.

Blood Plasma Can Support Treatment

The above has been discussed about blood plasma which has an important function in the body, especially for blood clotting. Moreover, blood plasma has other benefits for the immune system. In blood plasma substances that are important for these functions are contained, such as:

• Antibodies / immunoglobulins,
• Fibrinogen,
• Albumin, and
• Blood clotting factors.

Blood plasma can also be donated through blood donors.

When the blood has been obtained, the medical officer will separate the blood plasma and the contents in it. These contents will then be given to patients in need, as treatment.

In patients with rare chronic diseases such as hemophilia and autoimmune diseases, therapy can be given using proteins and antibodies found in blood plasma, in order to live longer and be productive in carrying out daily activities.

General Blood Function

As a special liquid circulating in the body, blood becomes very important because it has many functions, namely:

Transport Oxygen

The oxygen we breathe from the air is flowed into the body through the nose, and then into the heart and blood vessels. Through this vessel, oxygen is transported by blood and circulated throughout the body.

Oxygen-containing air will enter the lungs.

Furthermore, oxygen will dissolve in the layer of water that is on the surface of the alveolar membrane. You need to know that the alveolar wall membrane consists of a flat epithelial layer that has a thickness of about 10 mm.

The dissolved oxygen then diffuses through the epithelial cells and capillary endhothelium so that it can enter the capillary veins. Oxygen then enters the blood plasma and then diffuses into the red blood cells (erythrocytes).

This can happen because red blood cells contain hemoglobin (Hb) which functions to bind oxygen in the blood.

The process of bonding oxygen with hemoglobin is called deoxygenation which produces oxyhemoglobin compounds (HbO2).

Oxygen which can change to HbO2 is about 97%.

Whereas the remaining around 2-3% of oxygen is in the blood plasma which will be transported to all tissues of the human body.

Circulating Nutrition

As a style of blood transport, it also functions to transport food saris derived from food consumed.

Of course the food we eat cannot be transported directly by blood, but must go through the digestive process.

Foods that enter the body will be processed by the human digestive system so that they will turn into small molecules (micromolecules).

Foods that have become micromolecules will then be absorbed in the intestine and circulate throughout the body through blood vessels.

In general, this process of food absorption occurs in the small intestine of the jejunum and ileum. Foods that have undergone a digestive process will enter that part. When the absorption process is taking place small molecules of food will enter the capillary and lymph vessels.

Blood flows in the human body through respiratory devices. Through the arteries, blood transports the food saris derived from oxygen uptake.

In addition, blood also transports and circulates vitamins, proteins and carbohydrates obtained from the food we consume.

Circulating Hormones

Not only oxygen and nutrients, blood also functions to eliminate and distribute hormones. Blood transport hormones to the organs of the body that are the destination.

Hormones are protein compounds produced by several endocrine glands or dead-end glands.

It is called an appendicitis because there is no hormone disposal system in the body.
The hormone produced by several glands in the body will then be transported to its destination through the blood vessels.

For example, the antidiuretic hormone (ADH) produced by the hypothalamus (the part of the brain that functions to control the body) will flow to the kidneys.

The hormone functions to regulate the process of reabsorption of water in the formation of urine.

The hormone will then be selected by the exocrine gland. Non-beneficial hormones will be discharged through special channels, while useful hormones will be drained by blood throughout the body.

The hormone itself contains messages that will affect the metabolism of the cells that are targeted. So that when the hormone reaches its destination through the blood, it can affect protein synthesis and cell metabolism in that place.

Bringing Cell Oxidation Waste

In the respiratory process, oxygen is transported by blood to the heart. After being processed in the heart, blood then carries carbon dioxide out of the body.

Dioxide is a waste that is not formed by the body, and will be discarded when we exhale.

Not all substances transported by blood include substances that are useful for the body.

As an example in the discussion above it has also been mentioned that blood carries carbon dioxide which is a waste product from cell metabolism.

In addition, the blood excretion system has a function to transport various types of substances to be carried to the human excretion organs.

These organs include the kidneys, skin, and liver. In these organs will be separated between substances that are useful for the body and which are not useful.

Furthermore, these useless substances will be released through the skin in the form of sweat or in the kidneys in the form of urine

Against Germs and Bacteria

Blood also functions as the body’s metabolic activator. In the blood there are several types of cells that maintain the body’s metabolism.

These blood cells will attack germs or foreign objects that enter the bloodstream.

If the blood cells succeed in fighting off the foreign body, our body will not get the disease. Conversely, if blood cells are not able to fight the foreign body, then the body will be attacked by disease.

Heals Wounds

The part of the blood called platelets plays a role in healing wounds in the skin.

Platelets will produce a type of substance that can form blood to freeze. After the blood freezes, the platelets slowly cover the wound on the skin until the skin is closed and returned to normal.

The role of platelets as an element of blood clotting is very important.

If the platelet pieces in the blood are reduced, the wound will be difficult to treat due to the absence of substances that can freeze the blood and close the wound.

When a wound occurs, platelets produce thrombokinase enzymes that will replace prothrombin to thrombin with the help of vitamin K and Ca.

Thrombin will replace blood proteins, namely fibrinogen, into fibrin threads. These fibrin threads function like nets that trap red blood cells so they can stop flowing.

If only a small amount of platelet contained in the blood can make the wound difficult to treat. This is because there is not enough substance in the blood that can cover the wound and freeze the blood.

Body Temperature Regulator

The results of blood oxidation produce heat in the body.

If the oxidation process goes well, the body temperature will be normal. Blood also functions to keep our body temperature stable at a temperature of 36 to 37 degrees Celsius. Because the temperature of the human body is not affected by the condition of the environment, but by the circulatory system.

This can occur because body heat generated from the oxidation process can be flowed properly throughout the body through the circulatory system.

So if the oxidation process can run well, the heat energy produced can be spread evenly throughout the body.

Withholding Disease Seeds

Blood pieces function to hold the seeds of disease so that they do not spread throughout the body through blood. Thus, the body is protected from various diseases.

This blood function can occur due to the presence of white blood cells (leukocytes) in the blood. In general, leukocytes have a larger size than red blood cells.

There are at least 5 types of white blood cells in the human body, namely lymphocytes, neutrophils, monocytes, basophils, and eosinophils.

The number of neutrophils in white blood cells is at most by 60%.

The main function of neutrophils is to attack and kill disease bacteria that enter our bodies. The way it works is that at first neutrophils will envelop the bacteria and will then release substances that can kill bacteria.

The number of lymphocytes in leukocytes is approximately 20 to 30 percent. The function of lymphocytes is to produce antibodies of a type of protein that are useful for attacking bacteria.
The amount of monocytes in leukocytes is approximately 5 to 10 percent. Monocyte function is the same as lymphocyte function which is fighting and killing germs.

While the number of eosinophils in white blood cells is about 5 percent. The function of this type of white blood cell is to attack germs, remove the remnants of damaged cells, and control the amount of chemicals released when attacking germs.

The last is basophils which number about 1 percent. The function of basophils is to prevent clotting in human blood vessels