Human Circulatory System:

The human cardiovascular system and the circulatory system work together to fight off diseases. The human circulatory system helps to maintain a normal temperature in the body and provides necessary chemicals to the body. There are four major components of the circulatory system. They are:

Human Circulatory System
  1. The heart.
  2. Arteries.
  3. Veins.
  4. Blood. 

While breathing or inhaling oxygen enters the body and bloodstream through a tiny membrane in the lungs. After this, the body uses all the oxygen and processed nutrients. This results in the creation of carbon dioxide. Your lungs expel the carbon dioxide when you exhale. Similarly in your digestive system nutrients and hormones transports to the endocrine system through this process. The constant pressure from the valves of the heart makes sure if the veins are carrying blood to the heart and transports it away by the arteries. Blood circulation begins when the heart stops between two beats. The blood goes from the two atria to the ventricles and then expands. The lower stage is the expulsion period, which occurs when both ventricles pump blood to the large arteries. There are three types of circulation, Pulmonary circulation, Systemic circulation, and Coronary circulation. 

Parts Of Human Circulatory System:


Arteries are one of the components of a vast network of blood vessels in the human circulatory system. They help in carrying the oxygenated blood from the heart and deliver it to tissues of the body. Veins carry blood back to the heart. Arteries are the main kind of blood vessels that have thick walls. Blood in the arteries passes through a higher pressure than veins. Which is why the wall of the arteries are thicker and more elastic than veins. Arteries carry away blood in two specific ways, the systematic circuit and the pulmonary circuit. There are two types of arteries. 

  • Elastic arteries- they are closer to the heart and contain more elastic fibers. The blood pressure is highest in that place. Due to their elastic nature, they can expand and surge according to the heartbeat.
  • Muscular arteries- they are far away from the heart. The blood pressure in this location is very low. Muscular arteries have very smooth muscles and less elastic fibers. 

The main artery of the circulatory system is the aorta. It is the largest artery and is situated in the left ventricle. 


Capillaries are tiny blood vessels that help in connecting your arteries and veins. It also helps in exchanging certain important elements between blood and tissues. Capillaries are present in abundance in very active tissues. Some of these issues consist of the liver, muscles, and kidneys. The exchange of oxygen, nutrients, and waste between the tissues and blood happens in your capillaries. There are two processes in which this exchange happens, passive diffusion and pinocytosis. White blood cells from your immune system use capillaries for reaching the sites of infection and other inflammatory damage. There are three types of capillaries:

  1. Continuous capillaries.
  2. Fenestrated capillaries.
  3. Sinusoid capillaries.

When your capillaries widen you get birthmarks known as Port-wine stains. When capillaries lead blood into the skin, it results in petechiae. Petechiae is small, round red or purple color spots that appear in your skin. 


Veins come under the category of blood vessels in the human circulatory system. It usually helps in returning the deoxygenated blood from various organs to the heart. This whole mechanism is the venous system. The walls of the vein are tunica externa, tunica media, and tunica intima. There are at least 34 main veins that exist in your body with other small veins connecting with capillaries. There are 4 types of veins.

  1. Deep vein- these veins are mainly located in the muscle tissue. 
  2. Superficial veins- Superficial veins are close to the surface of the skin. They do not have proper nerves.
  3. Pulmonary veins- they carry oxygen from the lungs to the heart. Each lung has two sets of pulmonary arteries, one on the right and one on the left.
  4. Systemic veins- it extends from the body to the legs, including the arms and torso. They return deoxygenated blood to the heart.

Sometimes the serious condition can affect veins and blood vessels. 

Portal veins:

The portal vein is one of the main vessels of the portal venous system. It helps in draining the blood out from the gastrointestinal tract, gallbladder, pancreas, and spleen to the liver. It contributes 75% of its blood flow. It is about three to four inches long and is usually formed by a combination of superior mesenteric and splenic veins behind the upper edge of the pancreas. Portal vein obstruction results in massive damage to liver function.

Portal veins is not a true vein; thus, it brings nutrient-rich blood to the liver from the gastrointestinal blood and spleen. After that, the liver extracts out the nutrients and filter out the toxic substances from the blood before it goes back to the circulation. Portal hypertension is a disease that happens due to high blood pressure in the portal veins. 


The heart is one of the most important elements in the human circulatory system. This organ helps in pumping blood throughout the body. It supplies oxygen and nutrients to the tissues. Removes carbon dioxide and other waste. The human heart has four chambers. They are two upper chambers (the atria) and two lower ones (the ventricles). A wall of muscle, septum separates the two sides of the heart. The outer wall of the heart consists of three layers: epicardium, pericardium, and myocardium. The function of the heart is the pump oxygenated blood all over the body. It also pumps hormones and other vital substances. It also receives the deoxygenated blood and pumps it to the lungs to oxygenate it. Along with these it also helps in maintaining blood pressure.


The lungs are a pair of spongy and airy organs located on either side of the chest. The trachea carries inhaled air from its pulsed tubular branches to the lungs, called the bronchi. The bronchi divide into smaller and smaller branches, eventually becoming microscopic. Some of the functions of the lungs are the exchange of gases like oxygen and carbon dioxide, breathing, production of sound, and protecting your body from dust and microbes. Any kind of damage in the lungs will result in blowing air out. This type of condition is Chronic Obstructive pulmonary disease. Sometimes smoking can be the main cause of this kind of condition. Infection in both of the lungs results in pneumonia. Some other lung problems are asthma, acute bronchitis, pulmonary fibrosis, cystic fibrosis, lung cancer, tuberculosis, acute respiratory distress syndrome, etc.


People who have circulatory disease have a chance of getting one. The human circulatory system can have various problems. Being overweight or obese also increases your chances of getting a contagious disease. However, a healthy and active diet can reduce the risk. Exercise keeps the heart healthy by reducing the risk of high blood pressure, high cholesterol, and being overweight – all of which are risk factors for circulatory diseases. Also, avoid smoking and other bad habits like the consumption of alcohol. This will give you’re a better circulatory system.


What are the 3 types of the circulatory system?

The 3 parts of the human circulatory system are as follows:
Systematic circulation- in this circulation the blood circulates from the heart via arteries to the periphery. It comes back to the heart through veins. 
Pulmonary circulation- in this circulation the blood moves from the heart to the lungs and again back to the heart.
Portal circulation- in this circulation the blood moves from the gut area via the liver to the heart. it is also known as coronary circulation. 

What is the largest artery in the body?

The largest artery of the body is the aorta. It is the main high-pressure duct that connects to the left ventricle of the heart. The aorta branches into a network of small arteries that extend throughout the body. The small branches of an artery are arteries and capillaries. Damage to the aorta can lead to death. When your aorta damages, several internal bleedings occur, such as kidney failure or intestinal damage. There are two aortas connected by vessels. Each of them passes through gills.

What are some health issues of the circulatory system?

There are various types of human circulatory system issues. Some of them are as follows:
Heart attack
Mitral valve prolapses
Mitral valve regurgitation
Mitral stenosis
Angina pectoris
Arrhythmia and dysrhythmia
High cholesterol
Heart failure
Peripheral artery disease (PAD).
Circulatory issues links with each other. High blood pressure can damage blood vessels. Also narrowing of blood vessels will increase cholesterol. High cholesterol tends to clot blood in human beings.

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