The vascular system of the pulmonary circulation is directly involved in the gas exchange between the blood of the pulmonary capillaries and the alveolar air.

The venous blood flows from the heart to the lungs through the pulmonary trunk, and arterial blood flows from the lungs to the heart through the pulmonary veins.

The pulmonary circulation originates at the pulmonary trunk (truncus pulmonalis).

The artery arises from the right ventricle (ventriculus dexter).

It passes obliquely to the left, anteriorly to the ascending aorta, which it crosses in front.

Under the arch of the aorta at the level of the thoracic vertebrae 4-5, there is a bifurcation of the pulmonary trunk, where the pulmonary trunk divides into two arteries:

The right pulmonary artery (a. pulmonalis dextra)

The left pulmonary artery (a. pulmonalis sinistra)

Between the bifurcation of the pulmonary trunk and the arch of the aorta, there is a short arterial ligament (lig. arteriosum), which is a closed ductus arteriosus (Botallo’s duct).

The right pulmonary artery (a. pulmonalis dextra) arises from the pulmonary trunk (truncus pulmonalis).

It is located inferiorly to the ascending aorta and superior vena cava

Entering the root of the lung, it gives off three lobar branches:

The superior lobar artery (a. lobaris superior)

The middle lobar artery (a. lobaris media)

The inferior lobar artery (a. lobaris inferior)

Which in turn divide into segmental branches

The superior lobar artery (a. lobaris superior) gives off 5 branches

The apical branch (r. apicalis)

The posterior descending and ascending branches (rr.posteriores descendens et ascendens)

The anterior descending and ascending branches (rr. anteriores descendens et ascendens)

Two branches arise from the middle lobar artery (a. lobaris media):

the lateral branch (r. lateralis)

the medial branch (r. medialis)

The inferior lobar artery (a. lobaris inferior) divides into 5 branches:

The apical branch (r. apicalis)

and 4 basal branches

The medial basal branch (r. basalis medialis)

The anterior basal branch (r. basalis anterior)

The lateral basal branch (r. basalis lateralis)

The posterior basal branch (r.basalis posterior)

Which supply the corresponding segments of the right lung with blood.

The left pulmonary artery (a. pulmonalis sinistra) arises from the pulmonary trunk (truncus pulmonalis).

First, it goes superiorly, and then posteriorly, externally, and to the left to the hilum of the left lung.

On its way, it first crosses the left main bronchus, and in the hilum of the left lung, it is located above it.

The left pulmonary artery divides into two arteries in the area of the lung root:

The superior lobar artery (a. lobaris superior), which in turn gives off five branches

And the inferior lobar artery (a. lobaris inferior), which also gives off five branches

Branches of the superior lobar artery:

The apical branch (r. apicalis)

The anterior ascending and descending branches (rr. anteriores ascendens et descendens)

The posterior branch (r. posterior)

The lingular branch (r. lingularis)

Branches of the inferior lobar artery:

The superior branch (r. superior)

and four basal branches

The medial basal branch (r. basalis medialis)

The anterior basal branch (r. basalis anterior)

The lateral basal branch (r. basalis lateralis)

The posterior basal branch (r. basalis posterior)

Which supply blood to the corresponding segments of the right lung.

Anastomoses:

In the tissue, small branches of the pulmonary artery and bronchial branches of the thoracic aorta form systems of interarterial anastomoses.

This is the spot where blood travels a short way from the systemic circulation directly into the pulmonary circulation.

Veins of the pulmonary circulation

The venous system of the pulmonary circulation consists of the segmental veins eponymous with the arteries.

The segmental veins adhere to the arteries and nerves, forming single neurovascular bundles.

The venous system of the pulmonary ends with four large veins, which insert into the left atrium (atrium dextrum).

The common basal vein, fusing with the apical (superior) branch of the inferior lobe, forms the right inferior pulmonary vein

The right inferior pulmonary vein (v. pulmonalis dextra inferior) drains blood from five segments of the inferior lobe of the right lung: the apical (superior) and the basal (medial, lateral, anterior, and posterior).

The right superior pulmonary vein (v. pulmonalis dextra superior) is larger than the inferior one, as it drains blood from the superior and middle lobes of the right lung.

The left superior pulmonary vein (v. pulmonalis sinistra superior) drains blood from the superior lobe of the left lung (its apical, posterior and anterior, as well as superior and inferior lingular segments).

It has three tributaries: the posterior apical, anterior and lingular veins.

The left inferior pulmonary vein (v. pulmonalis sinistra inferior) is larger than the right vein of the same name, and it drains blood from the inferior lobe of the left lung.

Dictionary

Vessels of the pulmonarycirculation

Pulmonary trunk

truncus pulmonalis

Right ventricle

ventriculus dexter

Right pulmonary artery

a. pulmonalis dextra

Left pulmonary artery

a. pulmonalis sinistra

Arterial ligament

lig. arteriosum

Superior lobar artery

a. lobaris superior

Apical branch

r. apicalis

Posterior descending and ascending branches

rr. posteriores descendens et ascendens

Anterior descending and ascending branches

rr. anteriores descendens et ascendens

Middle lobar artery

a. lobaris media

Lateral branch

r. lateralis

Medial branch

r. medialis

Inferior lobar artery

a. lobaris inferior

Anterior basal branch

r. basalis anterior

Posterior basal branch

r. basalis posterior