What blood process does vitamin K help directly control?

Vitamin K plays a vital role in the process of blood clotting, which is essential for maintaining hemostasis—the body's ability to prevent and stop bleeding when injuries occur. It is a key element in the synthesis of certain proteins known as clotting factors, which are necessary for coagulation. Without adequate levels of vitamin K, these proteins cannot function properly, leading to an increased risk of excessive bleeding and difficulty in wound healing.

The other options do not relate directly to the primary function of vitamin K. Blood pressure is regulated by various factors, including vessel elasticity and the nervous system, but vitamin K does not play a role in this process. Blood filtration pertains to the kidneys' function in removing waste products from the blood, while blood oxygenation involves the exchange of oxygen and carbon dioxide in the lungs and tissues. Neither of these processes is influenced directly by vitamin K.