This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Abdomen and pelvis, Subject name: Anatomy
The opening of cystic duct is guarded by which of the following valve ? 
Select and explain. 
A. valve of haister, B. valve of wirsung, C. value of Santorini, D. valve of virchow.
A: valve of haister
Answer: A: valve of haister 
Explanation: Cystic duct is about 3 to 4 cm long. It begins at the neck of the gall bladder, runs downwards, backwards and to the left, and ends by joining the common hepatic duct at an acute angle to form the bile duct. The mucous membrane of the cystic duct forms a series of 5 to 12 crescentic folds , arranged spirally to form the so-called spiral valve of Heister. This is not a true valve. Ref : B D Chaurasia's Human Anatomy , seventh edition , volume 2 , pg . no., 316.