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Posterior segmental artery of left lung

The posterior segmental artery (A2) of the left lung is a branch of the left superior lobar artery, which arises from the left pulmonary artery. It specifically supplies the posterior segment (S2) of the left upper lobe, corresponding to the bronchopulmonary segment associated with the posterior segmental bronchus (B2).

The artery typically arises after the superior lobar artery divides near the hilum, coursing posteriorly and superiorly alongside the B2 bronchus. It travels within the parenchyma of the left upper lobe and divides into subsegmental branches that provide arterial blood to the alveoli and supporting structures of the posterior segment.

Anatomically, it is closely related to the apicoposterior segment (S1+2) bronchus in some cases, since S1 and S2 often share arterial supply. Variations include a common trunk with the apical segmental artery (A1) or separate origins. Knowledge of its anatomy is vital for segmentectomy, lobectomy, and CT-based pulmonary segmental mapping.

Synonyms

  • A2 artery of left lung

  • Posterior segmental branch of left superior lobar artery

  • Left lung posterior segmental pulmonary artery

Function

  • Provides oxygenated blood from the pulmonary circulation to the posterior segment (S2) of the left upper lobe

  • Works with the posterior segmental vein (V2) and posterior segmental bronchus (B2) to define the bronchopulmonary segment

  • Serves as an anatomical guide for segmental lung resections

  • Plays a role in segment-based imaging and surgical planning

Branches

  • Multiple subsegmental branches supplying alveoli within the posterior segment (S2)

  • May share a common trunk with A1 (apical segmental artery)

MRI Appearance
T1-weighted images:

  • Lumen appears as a signal void (black) with hypointense walls

  • Adjacent fat and lung tissue provide contrast for localization

T2-weighted images:

  • Artery lumen shows a flow void

  • Intraluminal thrombus or abnormal flow may appear intermediate to high signal

T2 TRUFISP (cardiac/respiratory-gated):

  • Visualizes A2 as a bright vascular channel branching posteriorly from the left superior lobar artery

  • Demonstrates dynamic flow and branching patterns in real time

STIR:

  • Fat suppression highlights the artery against surrounding lung tissue and hilum

  • Detects perivascular edema or inflammatory processes

T1 Post-Contrast (Gadolinium-enhanced MRI):

  • A2 enhances brightly and homogeneously with contrast

  • Filling defects reveal pulmonary emboli, stenosis, or extrinsic compression

MRI Non-Contrast Cardiac-Gated 3D Imaging:

  • Provides 3D visualization of segmental branching, showing A2’s course with respect to B2 and V2

  • Especially useful in preoperative planning for segmentectomy and congenital mapping without contrast

CT Appearance
CT Pulmonary Angiography (CTPA) / CT Coronary Angiography (CCTA):

  • Clearly demonstrates A2 branching from the left superior lobar artery and its course toward the posterior segment

  • Multiplanar reconstructions delineate its relationship with segmental bronchus and vein

  • Essential for identifying embolism, vascular stenosis, congenital anomalies, and surgical planning

  • Differentiates segmental arterial anatomy during CT-guided segmentectomy planning

CT image

Posterior segmental artery of left lung anatomy ct axial image -img-00000-00000

MRI image

Posterior segmental artery of left lung mri image