Which letter is labelling the posterior intercostal arteries?

Question

BlackTom AI · Accepted Answer

Posterior intercostal arteries arise from the descending (thoracic) aorta and run laterally in each intercostal space along the inferior border of the ribs within the costal groove.

1) Relevant knowledge points and concepts
- The posterior intercostal arteries are paired vessels branching directly from the thoracic (descending) aorta. 
- They travel laterally and posteriorly along the rib cage in each intercostal space, supplying intercostal muscles, overlying skin, vertebrae, and contributing spinal branches. 
- The descending aorta itself lies midline/prefers the posterior mediastinum; internal thoracic (anterior intercostal) arteries run more anteriorly along the sternum; common iliac arteries lie in the pelvis/lower abdomen.

2) Step‑by‑step reasoning from the image
- Identify the arrows: the arrow labeled B points to a series of small lateral branches running along the ribs at multiple levels. These match the expected course of posterior intercostal arteries (multiple paired arteries coursing laterally from the aorta into the intercostal spaces). 
- The arrow labeled D points to the midline vertical vessel (the descending thoracic aorta) — the origin of the posterior intercostal arteries, not the intercostal arteries themselves. 
- A at the top indicates the ascending/aortic arch region or great vessels; C points to the pelvic iliac region; E points more anteriorly/medially (internal thoracic or anterior intercostal branches).

3) Intermediate identification steps (visual matching)
- Multiple lateral, rib‑following red branches = intercostal arteries.
- Their posterior lateral position (near costal grooves) matches the posterior intercostal arterial anatomy.

4) Why B is correct
- B is pointing directly at the lateral branches following the ribs in each intercostal space, exactly the pathway and appearance of posterior intercostal arteries.

5) Why the other options are incorrect
- C labels a vessel in the pelvic region (common/external iliac) — not intercostal arteries. 
- D labels the descending thoracic aorta itself (the source), not the lateral posterior intercostal branches. 
- E is more anterior/medial and corresponds to internal thoracic/anterior intercostal vessels, not the posterior intercostal arteries.

Conclusion: The posterior intercostal arteries are correctly labeled by B. This confirms the provided answer: B.

Which letter is labelling the posterior intercostal arteries? 单项选择题

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