Which vessel layer maintains hemostasis?

• A. Tunica Intima
• B. Tunica Media
• C. Tunica Adventitia
• D. Endothelium'],"answer":0},{

Answer: (A)

Endothelium, the inner lining of blood vessels, directly maintains hemostasis. It provides a nonthrombogenic surface under normal conditions by secreting anticoagulant and antiplatelet factors such as nitric oxide, prostacyclin, heparan sulfate, and thrombomodulin, which help keep blood from clotting unnecessarily. It also helps regulate clotting when injury occurs, responding to damage by tipping the balance toward coagulation only when a breach needs to be sealed. While the tunica intima is the inner vessel layer that contains the endothelium, the specific component responsible for maintaining hemostasis is the endothelial layer itself. The other layers—tunica media (smooth muscle that controls vessel diameter) and tunica adventitia (supportive connective tissue)—do not primarily manage hemostasis.