Circulatory system


The complex nature of the human body demands an efficient circulatory system in order to sustain life. The trillions of cells which comprise the human body demand this efficiency in order to maintain the functions of the multitudes of systems within the human body, which represents an ingenious division of labor. The majority of the body’s cells are immobile, and therefore can not retrieve the basics of their existence independently. This means a well organized and efficient circulatory system is responsible for deliver life sustaining oxygen and nutrients to the cells which are incapable of fending for themselves.

The blood within the circulatory system is responsible for delivering this life sustaining oxygen and nutrients. The adult human body hosts nearly 60,000 miles of passageway for the blood, also known as the blood vessels, in order to effectively deliver life to the immobile cells.

The red blood cells, which are responsible for the delivery of oxygen and nutrients, can also deliver within its frame work, bacteria, fungus, infection, disease, and other life denying (to the cells) toxins that can compromise the integrity of the immobile cells. The human body has a built in defense system to counteract this situation and come to the aid of the compromised cells known as white blood cells. The white blood cells in conjunction with the lymphatic system are often able to target cells which are being attacked by a toxic element and come to their rescue like little warrior cells.

The circulatory system is not a stand alone system, and it requires the assistance of systems such as the respiratory, urinary, endocrine, digestive, and integumentary systems in order to maintain its proper function and give the body the life sustenance it requires to live. While the circulatory system has numerous functions, the various capabilities and functions of this intense system can be segregated into two basic responsibilities.
Circulatory system
Image: Circulatory System


Transportation of the substances necessary to maintain cellular metabolism is one of two main functions of the circulatory system. In conjunction with the respiratory system, red blood cells by the name of erythrocytes are responsible for the transportation of oxygen which are systematically delivered to the cells waiting throughout the body. The human body takes a breath, which enters the lungs. In the lungs, the oxygen molecules attach themselves to hemoglobin molecules, which reside within the erythrocytes, and then make their way via transport by these cells to cells in need of oxygen. Once the cells have used the oxygen which has been delivered, the carbon dioxide that they have produced are then transported back to the lungs and expelled in exhaled air.

The blood and lymph vessels work in conjunction with the digestive system in order for the circulatory system to perform the delivery of nutrition. When food is eaten it is broken down by the digestive system and the nutrients are absorbed through the wall of the intestines, which is then picked up by the blood vessels and carried off to the cells requiring the nutrition with a pit stop through the liver for nutrient absorption and toxic cleansing.

The wastes associated with excess waters, ions, plasma, and metabolic waste produced by the cells which were delivered their nutrients, are then filtered through capillaries which belong to the kidneys. From there wastes enter the kidney tubes and are excreted in urine.

The circulatory system is also responsible for the transportation of hormones through the blood stream. This contributes to the regulatory process of maintaining health of the endocrine system.

The second basic function associated with the circulatory system involves protection. It effectively protects against both injury and disease through clotting, white blood cells, and the process of phagocytosis. White blood cells called leukocytes fight off disease and foreign material in the body. The body becomes feverish in this action as it works harder to produce a greater number of leukocytes.

The body’s natural ability to clot prevents excessive bleeding when blood vessels are harmed or damaged. Excessive damage may cause bleeding faster than the body can create clotting agents, but in most cases the clotting agents cease bleeding for long periods of time.


The circulatory system and the cardiovascular system are often interchangeable and interdependent within their specified roles. The circulatory system relies on the cardiovascular system in order to assist it with transporting required cells, nutrients, or other key vitalities in the blood stream. Without the heart to pump the 5 liters of blood per minute through the average adult body, the cells would float aimlessly along in a limp bloodstream. The four chambered heart pumps blood with enough force that blood pressure plays a vital role in forcing the blood through the body in less than a minute. The blood vessels form a network throughout the body of thin tubes that act as the transporters for the blood and its vital nutrients and blood cells. Arteries and veins form additional pathways much like tributaries to supply blood to every extremity and crevice of the body.

The microscopic arteries are known as arterioles, while microscopic veins are known as venules. Each play a role in either delivering blood to the necessary body parts or returning used blood back for recirculation.

Blood leaves the arteries through a capillary system which contain the thinnest and smallest of all the veins in the body, with the exception of microscopic systems. Capillaries, which are basic functional unit of the circulatory system, are responsible for the exchange of fluids, blood cells, nutrients, and wastes. When tissue cells have utilized the oxygenation or the nutritional value from a blood cell, it is returned to the blood stream via capillaries.

Tissue fluid, also known as interstitial fluid, comes from fluid derived from the plasma and becomes protective liquid for tissues that are not surrounded by blood. A small percentage of this fluid is returned through the capillaries and is likely to enter the lymphatic system via the connective tissues around the blood vessels. Fluid within the lymphatic system, which is known as lymph, is then discharged back into the venous blood. Strategically placed lymph nodes are responsible for the cleansing of the lymph before it is returned for another use. This is the body’s natural form of recycling and the entire circulatory system is based on this notion of natural recycling.
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human anatomy Organs included in Circulatory system

Abdominal VeinsAortic Arch
Arteries of the Neck and HeadArteries of the Pelvis and the Lower ExtremityArteries of the Shoulder and the Upper Extremity
BloodBlood Supply to the BrainBlood vessels
Branches of the Aorta Abdominal RegionBranches of the Aorta Thoracic SectionConduction System of the Heart
External Carotid ArteriesFetal CirculationHeart
Hepatic Portal SystemLower Extremity VeinsPrinciple Arteries
Principle VeinsRoutes of CirculationThorax Veins
Veins Associated with the Head and NeckVeins of the Upper Extremity