Circulatory system: what is it, parts and characteristics

According to the latest calculations, an adult human being weighing 70 kilograms and 170 centimeters tall is made up of approximately 30 trillion cells.

Of all of them, a significant percentage includes red blood cells, since it is estimated that there are approximately 5 million of them per microliter of blood. If we take into account that a human being has about 5 liters of blood running through his ducts and bathing his organs, the number of total red blood cells shoots up.

These data exemplify that the circulatory system is one of the most important at a physiological level for the human being. Our tissues are "living" entities to a certain extent, as they generate waste substances that need to be dislodged and nutrients to perform metabolic functions. Without a network of fluid tissues that takes care of this work, the life of complex multicellular beings like us (beyond the jellyfish) would be impossible.

Yes, you read that correctly: blood is a liquid connective tissue. This is just one of the many curiosities that the circulatory system houses, and we will tell you all of them in the following lines.

• Related article: "The 12 systems of the human body (and how they work)"

Circulatory system: what is it and what are its parts?

From a physiological point of view, this apparatus is defined as that which contains the heart (the organ of life by excellence) and blood vessels, allowing it to move blood through the body and all the organs and tissues that support it. make up.

This conglomerate of tubes and fluids allows the organs to receive oxygen and nutrients and at the same time get rid of metabolic waste substances, potentially toxic if stored in excess.

In most of the informative sources, the lymphatic system (through which the lymph flows, worth the redundancy) is considered part of the circulatory system. For informational reasons, we will leave this second system for another opportunity.

Beyond these data, it is necessary to name, albeit briefly, each of its parts to know the circulatory system in its entirety. Go for it.

1. The heart

The heart is defined as the central organ of blood circulation, which in lower animals is the simple dilation of a vessel and in higher animals it is muscular, contractile, and has two, three or four cavities. You have read correctly, because not all organs of a cardiac nature are composed of two ventricles and two atria as in humans.

For example, amphibians have two atria and one ventricle, in which a mixture of oxygenated and partially deoxygenated blood is produced.

The heart it is considered the strongest muscular structure in our bodyIt beats tirelessly more than 3,000 million times throughout our lives and pumps more than 7,000 liters of blood daily, a figure that is inconceivable from a human point of view. 40-50% of all this cardiac output is carried by the liver.

• You may be interested in: "The 13 parts of the human heart (and their functions)"

2. Blood vessels

Here the veins, arteries and capillaries are included. We tell you quickly what each of these tubular and conductive structures consist of:

• Capillary vessels: they are small branches of the blood network that reach the most hidden corners of the body, since no tissue is free of them.
• Arteries: the vessels that distribute the oxygenated blood that comes from the lungs to the rest of the organs.
• Veins: the vessels that carry deoxygenated blood back to the heart and lungs so that it is oxygenated and, therefore, repeats the cycle.

We are before a blood tissue transport system that, if disrupted, can have serious consequences on the physiology of the individual. Have you ever heard of a death from thrombosis? In these cases, a plug or thrombus (generally made of fat or clotted blood) is generated in an artery and, by normal flow, it is transported to an area with a smaller diameter than the one from which it originated. When the thrombus cuts off blood flow, the effects on the individual's physiology can be lethal.

• You may be interested in: "The 7 differences between arteries and veins"

3. Blood

How can we leave the blood, the connective tissue that gives meaning to this whole system, in the inkwell? Blood is famous for its transport of oxygen (thanks to the Red blood cells, specifically to hemoglobin, the hemoprotein that transports it), but it also fulfills many other functions at an organic level.

For example, few people know that blood has a high concentration of circulating proteins (especially albumin, which represents up to 55% of the total), which help maintain plasma oncotic pressure and act as lipid and hormone transporters steroids. Oncotic pressure, for example, is essential for the body to functionas it allows extracellular fluids and blood volumes to be "in place". If a mismatch occurs, the famous and dreaded edema appear, that is, excessive accumulation of fluid under the skin or in certain body cavities.

The composition of the blood is distributed as follows: blood plasma (55%, acellular component) and formed components (the remaining 45%, composed of red blood cells, serum proteins and immune function leukocytes, among many others).

Between the functions of the blood, we find the most relevant to the following:

• Participate in the defense against infections, by the transport of white blood cells to the affected place.
• Participate in the transport of nutrients and oxygen to all cells of the body.
• Transport waste substances from tissues to lungs (in the case of CO2) and liver and kidneys.
• Participate in body thermoregulation.
• Transport hormones, enzymes, serum proteins and other substances of a regulatory nature as far as metabolism is concerned.
• Be essential for coagulation and healing, among other things by transporting platelets to the affected site.

Fun facts about the cardiovascular system

This is a series of data that exemplify the importance and functionality of the circulatory system at a physiological level. Among them, we find the following:

• From end to end, and comprising all the veins, capillaries and arteries, the circulatory system would cover about 100,000 kilometers.
• The heart pumps about 5 liters of blood per minute, that is, almost all of this fluid in the body in just 60 seconds.
• The heart and kidneys use about 500 kilocalories a day. Simply pumping and purifying blood accounts for ¼ of the total energy consumed each day.
• The heart beats about 80 times per minute, generating enough energy to move a vehicle from a theoretical point of view.

Among all this mass of data, we are struck by discovering that the vascular tissue of a human being, if it were to be lined up, would be enough to go around the Earth itself 2 and a half times. 80% of this value corresponds to blood capillaries, units in which veins and arteries branch.

Diseases and considerations

Did you know that, in developed countries, the leading cause of death is ischemic heart disease, only followed by heart attacks? The obstruction of the coronary arteries and blood flow are, shocking as it may seem, the main cause of death across the globe.

For the circulatory system to function at its best, it is essential to keep parameters such as cholesterol or body weight in check.

Overweight (present in more than 1,900 million inhabitants of the globe) and obesity (650 million of this total number) are factors proven risk factors for certain cardiovascular diseases, such as coronary heart disease, heart failure, fibrillation ear and the appearance of arrhythmias, among many others, not counting other risks such as colorectal cancer or ulcers stomach.

Definitely: maintaining a healthy body implies, in almost all cases, reducing the risk of death due to accidents of a circulatory nature.

Resume

We have made a brief tour of the circulatory system, since covering each and every one of the structures included here would give a whole saga of books. If we want you to have an idea, this is the following: the heart is the organ that works the most in living beings at the physiological and, thanks to it, each and every one of the organs and tissues are nourished and the excretion of substances potentially harmful.

Errors in the circulatory system are serious therefore, when the blood flow is cut off, isolated cells rapidly die irreversibly. Therefore, taking care of yourself on a physical and emotional level is always the best prevention to avoid a vascular accident.

Bibliographic references:

• Definition of circulatory system, NIH. Picked up on December 26 in https://www.cancer.gov/espanol/publicaciones/diccionario/def/sistema-circulatorio
• The circulatory system, Connecticuts children. Picked up on December 26 in https://www.connecticutchildrens.org/health-library/es/parents/heart-esp/
• Circulatory System, Medlineplus.gov. Picked up on December 26 in https://medlineplus.gov/spanish/ency/esp_imagepages/8747.htm
• Circulatory system, visiblebody.com. Picked up on December 26 in https://www.visiblebody.com/es/learn/circulatory