This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Surgery
An 85-year-old hypertensive man is evaluated in the emergency department for recent onset epistaxis. His blood pressure is 150/80 mm Hg, and hematocrit is 39%. What is the most likely source of bleeding? 
Select and explain. 
A. Posterior nasal septum, B. Anterior nasal septum, C. Inferior turbinate, D. Middle turbinate
A: Posterior nasal septum
Answer: A: Posterior nasal septum 
Explanation: Epistaxis in children and young adults usually arises from the anterior nasal septum (Kiessel bach's plexus). In elderly persons, however, spontaneous rupture of a sclerotic blood vessel in the posterior nasal septum is usually the cause of bleeding, especially in combination with hypertension.