The disclosed technology is directed to an endoscope comprises an operation portion. An insertion portion having respective proximal and distal ends. The proximal end is configured to be attached to the operation portion and the distal end is used to be inserted into a subject. The distal end of the insertion portion includes a distal surface having at least an observation window, a channel opening, and an elongated feed conduit having a slanted feed passage all which formed therein to communicate simultaneously with the operation portion and a procedure instrument during an operation on the subject. The elongated feed conduit having the slanted feed passage used to direct fluid into the subject. The slanted passage feed includes an ejection port that ejects the fluid from the slanted feed passage at an angle to generate a vortex flow so that mucus or mist-form particles are diffused away from the observation window.
