This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
Secondary retrosternal goitre derives its blood supply from : 
Select and explain. 
A. Mediastinal vessels, B. Thyroid vessels, C. Arch of aorta, D. Bronchial vessels
B: Thyroid vessels
Answer: B: Thyroid vessels 
Explanation: Secondary retrrosternal goitre : Is the extension of thyroid tissue to mediastinum from thyroid in the neck. and it derives blood supply from thyroid vessels.
Primary retrrosternal goitre : Is the ectopic thyroid tissue in the mediastinum and it derives blood supply from mediastinal vessels.