PCA9534A: Where does the sink current flow?

Hi,

I designed the PCA9543A to connects one Master device and two Slave devices.

If the master device makes the i2c signal low, Where does the sink current from the pull-up resistor tied to the i2c between the slave and PCA9543A flow?

Does the sink current sink across the PCA9543A to the master device? Or does it sink to the PCA9543A?

Thanks.