where does the jpouch come from?

Andrina, the pictures you’ve included would only both occur in a three-stage procedure. Here’s a description of that from the Cleveland Clinic:

The first phase consists of removing the colon, leaving the rectum behind, and giving the patient an end ileostomy for approximately six months. (Most patients report feeling considerably better after this surgery.)

The second phase consists of removing the remnant of rectum, creating a J-Pouch, doing an ileal anal anastomosis, with diverting loop ileostomy. The patient will have the diverting loop ileostomy for approximately three months as long as everything has healed. The third phase consists of closing the stoma. This should be a simpler procedure than stage one and two with a shorter duration and faster recovery.

So the J-pouch is fashioned from the final section of intestine that terminates in an end ileostomy in picture #1. It’s detached from the abdominal wall, pulled into the pelvis, formed into a J-pouch, and reattached to the rectal cuff. The loop ostomy is created upstream from there along the length of the intestine.

The image you've posted, its a little misleading.

The bottom section of the small intestine, I guess, about 6 inches, is stretched and folded back on itself, forming a U at the bottom, so in effect, now there are two tubes of small intestine sitting side by side; which are stitched together.

Then, the inner walls of both these intestinal tubes are cut down their length to create the J Pouch.

The bottom section, in the form of the U (mentioned earlier); an opening is created which is stapled to the inner anal sphincter/anus.

The key in fashioning a J Pouch is leaving a small rectal cuff that is nevertheless functional. It’s the only part made of colonic tissue.

My surgeon was the late Irwin Gelernt who was perhaps the best colorectal surgeon in the USA before he passed away in 1996. His work on my recital cuff has been repeatedly praised by my GIs for 26 years now.