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CIRCULATORY SYSTEM   The circulatory system is a network consisting of blood, blood vessels, and the heart. This network supplies tissues in the body with oxygen and other nutrients, transports hormones, and removes unnecessary waste products.

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CIRCULATORY SYSTEM   The circulatory system is a network consisting of blood, blood vessels, and the heart. This network supplies tissues in the body with oxygen and other nutrients, transports hormones, and removes unnecessary waste products.

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The heart
The heart is made of specialized cardiac muscle tissue that allows it to act as a pump within the circulatory system.

The human heart is divided into four chambers. There are one atrium and one ventricle on each side of the heart. The atria receive blood and the ventricles pump blood.

The human circulatory system consists of several circuits:

The pulmonary circuit provides blood flow between the heart and lungs.

The systemic circuit allows blood to flow to and from the rest of the body.

The coronary circuit strictly provides blood to the heart (not pictured in the figure below).

Blood and blood vessels

Blood from the heart is pumped throughout the body using blood vessels. Arteries carry blood away from the heart and into capillaries, providing oxygen (and other nutrients) to tissue and cells. Once oxygen is removed, the blood travels back to the lungs, where it is re-oxygenated and returned by veins to the heart.
https://en.wikipedia.org/wiki/Circulatory_system
https://www.khanacademy.org/science/high-school-biology/hs-human-body-systems/hs-the-circulatory-and-respiratory-systems/a/hs-the-circulatory-system-review

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(Image credit: Norman B/Shutterstock)

The circulatory system, also known as the cardiovascular system, is a vast network of organs and blood vessels that acts both as a delivery and waste removal system for the body. Nutrients, oxygen and hormones are delivered to every cell and as these necessities are provided, waste products such as carbon dioxide are removed, according to the nonprofit Nemours Children's Health System.

Not only does the circulatory system keep our cells healthy, but it also keeps us alive. The heart constantly receives signals from the rest of the body that direct how hard it needs to pump to properly supply the body with what it needs, according to Nemours. For example, when asleep, the body sends electrical signals to the heart that tell it to slow down. When participating in heavy exercise, the heart receives the message to pump harder to deliver extra oxygen to the muscles.

How the circulatory system works

The heart lies at the center of the circulatory system and pumps blood through the rest of the network. This hollow muscle is made up of four chambers: The left and right atriums make up the two chambers at the top and the left and right ventricles form the two chambers at the bottom, according to the University of Michigan. The chambers are separated by one-way valves to ensure that blood flows in the correct direction.

The rest of the circulatory system is made up of two independent networks that work together: The pulmonary and systemic systems.

The pulmonary system is responsible for providing fresh oxygen to the blood and removing carbon dioxide, according to the National Center for Biotechnology Information (NCBI). Oxygen-poor blood arrives from veins leading to the right atrium of the heart. The blood is then pumped through the right ventricle, then through the pulmonary artery, which splits off into two and divides into increasingly smaller arteries and capillaries before entering the lungs. The tiny capillaries form a network within the lungs that facilitate the exchange of carbon dioxide and oxygen. From the lungs, the oxygen-rich blood flows back toward the heart.

Next, the systemic system of arteries, veins and capillaries takes over. Arteries and veins are not the same, although they are both types of blood vessels. Arteries carry oxygen- and nutrient-rich blood from the heart to all parts of your body, according to the National Cancer Institute. Veins carry the oxygen- and nutrient-poor blood back to the heart. The capillaries are the smallest type of blood vessel, and provide the bridge between the arteries and veins.

(Image credit: Ross Toro, Livescience contributor)

As the oxygen-rich blood arrives from the lungs, it enters the left atrium and then travels through to the left ventricle before being pumped throughout the body, according to NCBI. The blood gets pumped through the aorta artery (the largest artery in the body) before entering the smaller arteries that carry the blood to every part of the body. As the blood delivers nutrients and oxygen to each cell, carbon dioxide and other waste products are picked up as the blood flows through the capillaries and into the veins.

The contraction and relaxation of the heart - the heartbeat - is controlled by the sinus node, which is a cluster of cells situated at the top of the right atrium. The sinus node sends electrical signals through the electrical conduction system of the heart that direct the muscle to contract or relax.

The heartbeat is divided into two phases: the systole and diastole phases. In the first, the ventricles contract and push blood out into the pulmonary artery or the aorta. At the same time, the valves separating the atria and ventricles snap shut to prevent blood from flowing backwards. In the diastole phase, the valves connecting to the atrium open, and the ventricles relax and fill with blood. The sinus node controls the pace of these two phases.

Adult humans have a total of about five to six quarts (a little less than five to six liters) of blood pumping through their bodies, according to Arkansas Heart Hospital. On average, the heart pumps about 100,000 times per day, pushing about 2,000 gallons (7,570 liters) of blood through a total of 60,000 miles (96,560 kilometers) of blood vessels. It only takes about 20 seconds for blood to travel through the entire circulatory system.

Circulatory system diseases

Heart disease is the leading cause of death for both men and women in the United States, claiming 610,000 people per year, according to the Centers for Disease Control and Prevention.

Heart disease is a broad term that covers a wide range of diseases and disorders, including (the blockage of blood to the brain), heart attack (the flow of blood to the heart is blocked), hypertension (high blood pressure causing the heart to work harder), arteriosclerosis (the arteries become thick and stiff) and aneurysm (a damaged blood vessel that can lead to internal bleeding).

Wondering how to improve your circulation (opens in new tab)? Risk factors for heart disease include age, sex, family history, poor diet, smoking and stress, as well as high blood pressure and elevated cholesterol levels, according to the Mayo Clinic. There are many ways that heart disease can be prevented, including keeping other health conditions under control, maintaining a healthy diet, participating in regular physical activity and keeping stress levels at a minimum.
Additional resources: This article was updated on Aug. 8, 2019, by Live Science Contributor Rachel Ross.

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Circulatory System: Facts, Function & Diseases

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(Image credit: Norman B/Shutterstock) The circulatory system, also known as the cardiovascular system, is a vast network of organs and blood vessels that acts both as a delivery and waste removal system for the body.

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Deoxygenated blood from the body enters the right atrium.

It flows through the tricuspid valve into the right ventricle. The term tricuspid refers to the three flaps of tissue that make up the valve.

Contraction of the ventricle then closes the tricuspid valve and forces open the pulmonary valve.

Blood flows into the pulmonary artery.

This branches immediately, carrying blood to the right and left lungs.

Here the blood gives up carbon dioxide and takes on a fresh supply of oxygen.

The capillary beds of the lungs are drained by venules that are the tributaries of the pulmonary veins.

Four pulmonary veins, two draining each lung, carry oxygenated blood to the left atrium of the heart.

https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_Biology_(Kimball)/Unit_15%3A_The_Anatomy_and_Physiology_of_Animals/15.03%3A_Circulatory_Systems/15.3A%3A_Anatomy_of_Human_Circulatory_System

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From the left atrium,

Blood flows through the mitral valve (also known as the bicuspid valve) into the left ventricle.

Contraction of the ventricle closes the mitral valve and opens the aortic valve at the entrance to the aorta.

The first branches from the aorta occur just beyond the aortic valve still within the heart.

Two openings lead to the right and left coronary arteries, which supply blood to the heart itself. Although the coronary arteries arise within the heart, they pass directly out to the surface of the heart and extend down across it. They supply blood to the network of capillaries that penetrate every portion of the heart.

The capillaries drain into two coronary veins that empty into the right atrium.

The Systemic Circulation

The remainder of the system is known as the systemic circulation. The graphic shows the major arteries (in bright red) and veins (dark red) of the system. Blood from the aorta passes into a branching system of arteries that lead to all parts of the body. It then flows into a system of capillaries where its exchange functions take place.
Blood from the capillaries flows into venules which are drained by veins.

Veins draining the upper portion of the body lead to the superior vena cava.

Veins draining the lower part of the body lead to the inferior vena cava.

Both empty into the right atrium.

https://www.youtube.com/watch?v=CWFyxn0qDEU

https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_Biology_(Kimball)/Unit_15%3A_The_Anatomy_and_Physiology_of_Animals/15.03%3A_Circulatory_Systems/15.3A%3A_Anatomy_of_Human_Circulatory_System

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Atherosclerosis and coronary artery disease

Atherosclerosis, also known as hardening of the arteries, occurs when plaque builds up on the walls of your arteries and eventually blocks blood flow. Plaque is made of cholesterol, fat, and calcium.

Coronary artery disease indicates that the plaque buildup in your arteries has caused the arteries to narrow and harden. Blood clots can further block the arteries.

HEART ATTACK
A heart attack occurs when not enough blood reaches your heart. This can happen due to artery blockage. Heart attacks damage the heart muscle and are medical emergencies.
SYMPTOMS

Pain in the center or left side of the chest that feels like mild or severe discomfort, pressure, fullness, or squeezing

pain that radiates from the jaw, shoulder, arm, or across the back

shortness of breath

sweating

nausea

irregular heartbeat

unconsciousness

https://www.healthline.com/health/circulatory-system-diseases#heart-attacks

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Congenital Heart Disease

This is a problem in one or more parts of the heart or blood vessels. It happens before birth.

About 8 out of every 1,000 children get it. They may have symptoms at birth, but some people with it don't have symptoms until childhood or even adulthood.

In most cases, we don't know why it happens. Genes may play a role, or it can happen if a baby is exposed to viral infections, alcohol, or drugs before it's born.

Heart Valve Disease

Your valves sit at the exit of each of your four heart chambers. They keep blood flowing through your heart.

Sometimes, there are problems with these valves. Examples of heart valve problems include:

Aortic stenosis. Your aortic valve narrows. It slows blood flow from your heart to the rest of your body.

Mitral valve insufficiency. Your mitral valve doesn't close tightly enough. This causes blood to leak backward, leading to fluid backup in the lungs.

Mitral valve prolapse. The valve between your left upper and left lower chambers doesn't close right.

Pericarditis

This condition is rare and means the lining surrounding your heart is inflamed. An infection often causes this.

Rheumatic Heart Disease

This happens when rheumatic fever, an inflammatory disease that's most common in children, damages your heart valves.

Rheumatic fever starts with untreated strep throat and can affect many parts of your child's body. If your doctor thinks your child may have had rheumatic fever, they'll do a physical exam and give tests including X-rays and EKGs to look for heart damage.

Stroke

Strokes happen when something slows or blocks blood flow to your brain. Your brain can't get the oxygen and nutrients it needs, and brain cells start to die. When blood can't get to the part of your brain that controls a certain function, your body doesn't work like it should.

A stroke can happen because of a blocked artery or a leaking or burst blood vessel. It needs immediate treatment to limit brain damage and other complications.

Stroke is the leading cause of disability and one of the top causes of death in the United States.

Other Vascular Diseases

Your circulatory system is made up of the vessels that carry blood to every part of your body.

Vascular disease includes any condition that affects your circulatory system. These include diseases of the arteries that go to your legs (peripheral vascular disease) and slow blood flow to your brain, causing strokes.

Cardiovascular Disease Treatments

Treatments for cardiovascular diseases can differ by the type of condition. Yours may include:

Changing parts of your lifestyle like your diet, exercise, and alcohol and tobacco use

Medications, including ones that treat risk factors like blood pressure or cholesterol or to break up clots

Medical procedures like having a balloon or stent placed in your blood vessel, heart valve surgery, or coronary artery bypass graft surgery.

Coronary Artery Disease

You may hear this called CAD. It's when plaque builds up and hardens the arteries that give your heart vital oxygen and nutrients. That hardening is also called atherosclerosis.

Deep Vein Thrombosis and Pulmonary Embolism

Blood clots can form in your deep veins, usually in your legs. This is deep vein thrombosis (DVT). They can break loose and travel through your bloodstream to your lungs, where they can block blood flow. This condition is called pulmonary embolism. It's life threatening and needs immediate medical attention.

You might be at higher risk of DVT because of your genes or family history. Other things that can increase risk include sitting for a long time, like in a car or on a plane; long-term bed rest; pregnancy; and using birth control pills or hormone replacement.

Heart Failure

This term can be scary. It doesn't mean your heart has "failed," or stopped working. It means your heart doesn't pump as strongly as it should. This will cause your body to hold in salt and water, which will give you swelling and shortness of breath.

Heart failure is a major health problem in the United States, affecting more than 6.5 million people. It is the leading cause of hospitalization in people older than 65.

The number of people diagnosed with heart failure is projected to rise 46% by 2030, according to the American Heart Association.

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This is a problem in one or more parts of the heart or blood vessels. It happens before birth. About 8 out of every 1,000 children get it. They may have symptoms at birth, but some people with it don't have symptoms until childhood or even adulthood.

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https://www.youtube.com/watch?v=UMTDmP81mG4
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