Systemic and pulmonary circulation

Systemic and pulmonary circulationOverview of the systemic and pulmonary circulation
~ 4 min

The cardiovascular system is a system of organs that ensures the delivery of substances necessary for vital activity to all cells and tissues of our body.

Circles of blood circulation
Circles of blood circulation
Heart, aorta and branches extending from it – front view
Heart, aorta and branches extending from it – front view

It consists of three components:

  • The heart (cor), which acts as a kind of pump for blood

  • Vessels (vasa), which perform a transport function by distributing blood throughout the body

And blood itself, which contains oxygen, as well as nutrients.

Heart (cor) – front view
Heart (cor) – front view
Vessels (vasa)
Vessels (vasa)

The heart, together with the vessels, forms two closed circuits, where two types of circulation take place.

There are two types of blood circulation:

The systemic circulation (circulus sanguinis major)

The pulmonary circulation (circulus sanguinis minor)

Pulmonary circulation (circulus sanguinis minor)
Pulmonary circulation (circulus sanguinis minor)
Systemic circulation (circulus sanguinis major)
Systemic circulation (circulus sanguinis major)

The pulmonary circulation delivers blood from the heart to the lungs, where it becomes saturated with oxygen and returns to the heart.

The systemic circulation then delivers the blood to the tissues and organs, supplying them with oxygen and nutrients. The blood then returns to the heart, and the cycle repeats.

Let’s consider both types of circulation in greater detail.

The pulmonary circulation originates in the right ventricle of the heart (ventriculus dexter).

Right ventricle of the heart (ventriculus dexter)
Right ventricle of the heart (ventriculus dexter)
Right ventricle of the heart (ventriculus dexter)
Right ventricle of the heart (ventriculus dexter)
Right ventricle of the heart (ventriculus dexter)
Right ventricle of the heart (ventriculus dexter)

From there, deoxygenated (oxygen-free) blood is pushed into a large vessel called pulmonary trunk (truncus pulmonalis).

Pulmonary trunk (truncus pulmonalis)
Pulmonary trunk (truncus pulmonalis)
Pulmonary trunk (truncus pulmonalis)
Pulmonary trunk (truncus pulmonalis)

Next, the pulmonary trunk divides into two pulmonary arteries.

These are the right pulmonary artery (arteria pulmonalis dextra)

And the left pulmonary artery (arteria pulmonalis sinistra)

Right pulmonary artery (arteria pulmonalis dextra) – back view
Right pulmonary artery (arteria pulmonalis dextra) – back view
Left pulmonary artery (arteria pulmonalis sinistra) – front view
Left pulmonary artery (arteria pulmonalis sinistra) – front view

They deliver blood to the right and left lungs, respectively.

The place of bifurcation is called bifurcation of the pulmonary trunk (bifurcatio trunci pulmonalis).

Pulmonary trunk (bifurcatio trunci pulmonalis)
Pulmonary trunk (bifurcatio trunci pulmonalis)

It is located at the level of the body of the 4th thoracic vertebra and 2nd intercostal space.

After that, the pulmonary arteries divide into smaller branches, and eventually into capillaries that form the microcirculatory bloodstream. This is where the blood gets saturated with oxygen and goes into the branches of the pulmonary veins.

Microcirculation of the lungs
Microcirculation of the lungs
Microcirculation of the lungs
Microcirculation of the lungs

These branches carry oxygenated blood into four large pulmonary veins.

The left superior pulmonary vein (vena pulmonalis sinistra superior)

The left inferior pulmonary vein (vena pulmonalis sinistra inferior)

The right superior pulmonary vein (vena pulmonalis dextra superior)

The right inferior pulmonary vein (vena pulmonalis dextra inferior)

Right pulmonary vein (vena pulmonalis dextra)
Right pulmonary vein (vena pulmonalis dextra)
Left pulmonary vein (vena pulmonalis sinistra)
Left pulmonary vein (vena pulmonalis sinistra)
Right superior and inferior pulmonary vein (vena pulmonalis dextra superior et inferior)
Right superior and inferior pulmonary vein (vena pulmonalis dextra superior et inferior)
Left superior and inferior pulmonary vein (vena pulmonalis sinistra superior et inferior)
Left superior and inferior pulmonary vein (vena pulmonalis sinistra superior et inferior)

Then the pulmonary veins flow into the left atrium (atrium sinistrum). This concludes the cycle of the pulmonary circulation.

Left atrium (atrium sinistrum)
Left atrium (atrium sinistrum)
Left atrium (atrium sinistrum)
Left atrium (atrium sinistrum)
Left atrium (atrium sinistrum)
Left atrium (atrium sinistrum)

Pay close attention here. The pulmonary arteries carry venous blood, but at the same time they are called arteries, since they go in the direction AWAY FROM the heart. And the pulmonary veins deliver arterial blood, but they are called veins because they go TOWARD the heart.

Arteries (arteriae) – from the heart
Arteries (arteriae) – from the heart
Vein (venae) – to the heart
Vein (venae) – to the heart

From the left atrium, blood flows into the left ventricle (ventriculus sinister), where the systemic circulation originates.

Left ventricle (ventriculus sinister)
Left ventricle (ventriculus sinister)
Left ventricle (ventriculus sinister)
Left ventricle (ventriculus sinister)
Left ventricle (ventriculus sinister)
Left ventricle (ventriculus sinister)

From the left ventricle, oxygenated blood is pushed into a large arterial vessel called the aorta (aorta).

Aorta (aorta)
Aorta (aorta)
Aorta (aorta)
Aorta (aorta)
Aorta (aorta)
Aorta (aorta)

It has the following parts:

The ascending aorta (pars ascendens aortae)

Arch of the aorta (arcus aortae)

The descending aorta (pars descendens aortae)

Ascending aorta (pars ascendens aortae) – front view
Ascending aorta (pars ascendens aortae) – front view
Arch of the aorta (arcus aortae) – front view
Arch of the aorta (arcus aortae) – front view
Descending aorta (pars descendens aortae) – front view
Descending aorta (pars descendens aortae) – front view

In turn, the descending aorta divides into two parts:

The thoracic aorta (aorta thoracica)

The abdominal aorta (aorta abdominalis)

Thoracic aorta (aorta thoracica)
Thoracic aorta (aorta thoracica)
Abdominal aorta (aorta abdominalis)
Abdominal aorta (aorta abdominalis)

Along its course, the aorta gives off many branches that distribute blood to all tissues and organs of the human body.

In the thickness of each of the organs, a microcirculatory bloodstream is formed, where the gas exchange occurs again: the blood supplies tissues with oxygen, taking carbon dioxide.

Microcirculation of tissues and organs
Microcirculation of tissues and organs
Microcirculation of tissues and organs
Microcirculation of tissues and organs

Then venous (or deoxygenated) blood passes into the venous tributaries, and then into the bloodstream of the hollow veins.

These are the superior vena cava (vena cava superior)

And the inferior vena cava (vena cava inferior)

Inferior vena cava (vena cava inferior)
Inferior vena cava (vena cava inferior)
Superior vena cava (vena cava superior)
Superior vena cava (vena cava superior)
Superior vena cava (vena cava superior)
Superior vena cava (vena cava superior)
Inferior vena cava (vena cava inferior)
Inferior vena cava (vena cava inferior)

Eventually, both hollow veins end by the right atrium (atrium dextrum). This concludes the cycle of the systemic circulation.

Right atrium (atrium dextrum)
Right atrium (atrium dextrum)
Right atrium (atrium dextrum)
Right atrium (atrium dextrum)
Right atrium (atrium dextrum)
Right atrium (atrium dextrum)
Dictionary

Systemic and pulmonary circulation

Pulmonary trunk
truncus pulmonalis
Right and left pulmonary arteries
arteria pulmonalis dextra et sinistra
Bifurcation of thepulmonary trunk
bifurcation truncipulmonalis
Left superior and inferior pulmonary veins
vena pulmonalis sinistra superior et inferior
Right superior and inferior pulmonary veins
vena pulmonalis dextra superior et inferior
Aorta
aorta
Superior vena cava
vena cava superior
Inferior vena cava
vena cava inferior
Ascending aorta
pars ascendens aortae
Arch of the aorta
arcus aortae
Descending aorta
pars descendens aortae
Thoracic aorta
aorta thoracica
Abdominal aorta
aorta abdominalis
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