Discovering the Flow of The Human Heart
WHAT IS THE CIRCULATORY SYSTEM?
The circulatory system is a network that allows blood to flow throughout the body, delivering oxygen and nutrients to cells while removing waste products like carbon dioxide. The system consists of the heart, blood vessels, and blood itself. Working with the respiratory system, it ensures that oxygen reaches tissues and carbon dioxide is expelled. Without the circulatory system, our cells wouldn’t receive the necessary materials to function properly, and waste products would build up, causing harm.
THE HEART
STRUCTURE AND FUNCTION
The heart is a muscular organ located in the chest, slightly to the left of the center. It acts as the body’s pump, ensuring that blood keeps moving through the circulatory system. The heart has four chambers: two atria on top and two ventricles on the bottom. These chambers work together to pump oxygen-poor blood to the lungs and oxygen-rich blood to the rest of the body. The heart contracts and relaxes in a regular rhythm, known as a heartbeat, ensuring a continuous flow of blood.
TYPES OF BLOOD VESSELS
There are three main types of blood vessels: arteries, veins, and capillaries. Arteries carry oxygenated blood away from the heart to the body. They have thick, elastic walls to withstand the high pressure from the heart’s pumping action. Veins bring deoxygenated blood back to the heart. They have thinner walls and often contain valves to prevent blood from flowing backward. Capillaries are tiny blood vessels that connect arteries and veins. These thin-walled vessels are where oxygen, nutrients, and waste are exchanged between blood and tissues.
HOW BLOOD CIRCULATES THROUGH THE BODY?
Blood circulates through two major loops: pulmonary circulation and systemic circulation. In pulmonary circulation, blood flows from the heart to the lungs, where it picks up oxygen and releases carbon dioxide. This oxygen-rich blood then returns to the heart. In systemic circulation, the heart pumps this oxygenated blood to the rest of the body. As blood moves through the body’s tissues, it delivers oxygen and collects waste products, like carbon dioxide, which are then transported back to the heart and lungs.
THE CARDIAC CYCLE
The heart works by contracting and relaxing in a cycle called the cardiac cycle. When the heart contracts (called systole), it pumps blood out of the ventricles into the arteries. When the heart relaxes (called diastole), it fills with blood again. The heart’s “lub-dub” sound comes from the valves opening and closing during this cycle. The right side of the heart pumps blood to the lungs, while the left side pumps oxygen-rich blood to the rest of the body. This continuous process keeps our blood flowing and cells supplied with oxygen.
Deoxygenated blood comes from the upper&lower body.
SYSTEMIC RETURN
Superior/Inferior Vena Cava; venous return dynamics and preload.
RIGHT ATRIUM
The right atrium receives oxygen-poor blood from the body and pumps it into the right ventricle.
TRICUSPID VALVE
One-way gate between the right atrium and the right ventricle, allowing deoxygenated blood to flow into the ventricle during relaxation. When the ventricle contracts, the valve closes tightly to prevent blood from leaking backward, ensuring it is properly pumped to the lungs for oxygenation
RIGHT VENTRICLE
The right ventricle pumps oxygen-poor blood to the lungs via the pulmonary arteries.
PULMONARY VALVE
One-way gate between the right ventricle and the pulmonary artery, opening to allow blood to travel to the lungs for oxygenation. Once the ventricle relaxes, it snaps shut to prevent the blood from flowing backward into the heart.
Deoxygenated blood moves to lungs.
PULMONARY ARTERIES
Blood vessels that carry oxygen-poor blood from the right side of the heart to the lungs.
LUNGS = GAS EXCHANGE
In your lungs, the blood loses carbon dioxide (which you breathe out) and gains fresh oxygen (from the air you breathe in).
This newly oxygen-rich (oxygenated) blood then travels back to your heart, which pumps it out to the rest of your body.
PULMONARY VEINS
Oxygenated blood comes from the lungs.
Blood vessels that carry oxygen-rich blood from the lungs to the heart.
LEFT ATRIUM
The left atrium receives oxygen-rich blood from the lungs and pumps it into the left ventricle.
MITRAL VALVE
Regulates blood flow by opening to allow oxygen-rich blood to pass from the left atrium into the left ventricle. When the ventricle contracts, the valve closes tightly to prevent blood from leaking back into the atrium, ensuring it is pumped out to the rest of the body
LEFT VENTRICLE
The left ventricle pumps oxygen-rich blood to the rest of the body via the aorta.
AORTIC VALVE
One-way gateway between the left ventricle and the aorta, opening to allow oxygen-rich blood to be pumped out to the rest of the body. When the heart relaxes, the valve closes tightly to prevent blood from flowing backward into the left ventricle.
Oxygenated blood moves through the body.
ASCENDING AORTA
Serves as the initial segment of the body's main artery, receiving oxygen-rich blood directly from the left ventricle. It delivers this blood to the coronary arteries, which supply the heart muscle itself, before the vessel arches to distribute blood to the rest of the body.
SUPERIOR VENA CAVA
AORTA
PULMONARY ARTERIES
Let’s put it all together!
PULMONARY VEINS
LEFT ATRIUM
LEFT VENTRICLE
RIGHT ATRIUM
RIGHT VENTRICLE
Blood Flow Through Heart
Nellie
Created on April 23, 2026
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Transcript
Discovering the Flow of The Human Heart
WHAT IS THE CIRCULATORY SYSTEM?
The circulatory system is a network that allows blood to flow throughout the body, delivering oxygen and nutrients to cells while removing waste products like carbon dioxide. The system consists of the heart, blood vessels, and blood itself. Working with the respiratory system, it ensures that oxygen reaches tissues and carbon dioxide is expelled. Without the circulatory system, our cells wouldn’t receive the necessary materials to function properly, and waste products would build up, causing harm.
THE HEART
STRUCTURE AND FUNCTION
The heart is a muscular organ located in the chest, slightly to the left of the center. It acts as the body’s pump, ensuring that blood keeps moving through the circulatory system. The heart has four chambers: two atria on top and two ventricles on the bottom. These chambers work together to pump oxygen-poor blood to the lungs and oxygen-rich blood to the rest of the body. The heart contracts and relaxes in a regular rhythm, known as a heartbeat, ensuring a continuous flow of blood.
TYPES OF BLOOD VESSELS
There are three main types of blood vessels: arteries, veins, and capillaries. Arteries carry oxygenated blood away from the heart to the body. They have thick, elastic walls to withstand the high pressure from the heart’s pumping action. Veins bring deoxygenated blood back to the heart. They have thinner walls and often contain valves to prevent blood from flowing backward. Capillaries are tiny blood vessels that connect arteries and veins. These thin-walled vessels are where oxygen, nutrients, and waste are exchanged between blood and tissues.
HOW BLOOD CIRCULATES THROUGH THE BODY?
Blood circulates through two major loops: pulmonary circulation and systemic circulation. In pulmonary circulation, blood flows from the heart to the lungs, where it picks up oxygen and releases carbon dioxide. This oxygen-rich blood then returns to the heart. In systemic circulation, the heart pumps this oxygenated blood to the rest of the body. As blood moves through the body’s tissues, it delivers oxygen and collects waste products, like carbon dioxide, which are then transported back to the heart and lungs.
THE CARDIAC CYCLE
The heart works by contracting and relaxing in a cycle called the cardiac cycle. When the heart contracts (called systole), it pumps blood out of the ventricles into the arteries. When the heart relaxes (called diastole), it fills with blood again. The heart’s “lub-dub” sound comes from the valves opening and closing during this cycle. The right side of the heart pumps blood to the lungs, while the left side pumps oxygen-rich blood to the rest of the body. This continuous process keeps our blood flowing and cells supplied with oxygen.
Deoxygenated blood comes from the upper&lower body.
SYSTEMIC RETURN
Superior/Inferior Vena Cava; venous return dynamics and preload.
RIGHT ATRIUM
The right atrium receives oxygen-poor blood from the body and pumps it into the right ventricle.
TRICUSPID VALVE
One-way gate between the right atrium and the right ventricle, allowing deoxygenated blood to flow into the ventricle during relaxation. When the ventricle contracts, the valve closes tightly to prevent blood from leaking backward, ensuring it is properly pumped to the lungs for oxygenation
RIGHT VENTRICLE
The right ventricle pumps oxygen-poor blood to the lungs via the pulmonary arteries.
PULMONARY VALVE
One-way gate between the right ventricle and the pulmonary artery, opening to allow blood to travel to the lungs for oxygenation. Once the ventricle relaxes, it snaps shut to prevent the blood from flowing backward into the heart.
Deoxygenated blood moves to lungs.
PULMONARY ARTERIES
Blood vessels that carry oxygen-poor blood from the right side of the heart to the lungs.
LUNGS = GAS EXCHANGE
In your lungs, the blood loses carbon dioxide (which you breathe out) and gains fresh oxygen (from the air you breathe in).
This newly oxygen-rich (oxygenated) blood then travels back to your heart, which pumps it out to the rest of your body.
PULMONARY VEINS
Oxygenated blood comes from the lungs.
Blood vessels that carry oxygen-rich blood from the lungs to the heart.
LEFT ATRIUM
The left atrium receives oxygen-rich blood from the lungs and pumps it into the left ventricle.
MITRAL VALVE
Regulates blood flow by opening to allow oxygen-rich blood to pass from the left atrium into the left ventricle. When the ventricle contracts, the valve closes tightly to prevent blood from leaking back into the atrium, ensuring it is pumped out to the rest of the body
LEFT VENTRICLE
The left ventricle pumps oxygen-rich blood to the rest of the body via the aorta.
AORTIC VALVE
One-way gateway between the left ventricle and the aorta, opening to allow oxygen-rich blood to be pumped out to the rest of the body. When the heart relaxes, the valve closes tightly to prevent blood from flowing backward into the left ventricle.
Oxygenated blood moves through the body.
ASCENDING AORTA
Serves as the initial segment of the body's main artery, receiving oxygen-rich blood directly from the left ventricle. It delivers this blood to the coronary arteries, which supply the heart muscle itself, before the vessel arches to distribute blood to the rest of the body.
SUPERIOR VENA CAVA
AORTA
PULMONARY ARTERIES
Let’s put it all together!
PULMONARY VEINS
LEFT ATRIUM
LEFT VENTRICLE
RIGHT ATRIUM
RIGHT VENTRICLE