What biological structure limits the straight vertical downward movement if the spleen normally does not descend below the costal margin?

The correct answer isthe left colic flexure. This is basically like a drop off a cliff; it’s the deep, sudden downward turn that the colon takes. This means that when the spleen is enlarged, it has to avoid that. The spleen, for those who don’t know, is located just left of that flexure. When you can’t go left, you’ll go medially so that you’re not interfering with the proper bodily functions more than you have to.

All half-joking aside, the left colic flexure is the reason the spleen will expand medially (or, towards the middle of the body) instead of towards the flexure. It prevents the expansion downward, making it easier for doctors to notice an issue since the expansion is contained in one area.

Left colic flexure-the left colic flexure, also called the splenic flexure, is the point where the colon takes a sharp downward turn. this flexure is the point where the transverse colon ends and the descending colon begins. it is located immediately inferior to the spleen, so an enlarged spleen must move medially to avoid this colic flexure. the left suprarenal gland is a retroperitoneal structure which sits superior to the kidney. the suspensory muscle of the duodenum or ligament of treitz is a thin sheet of muscle derived from the right crus of the diaphragm-it suspends the fourth part of the duodenum from the posterior abdominal wall. both the pancreas and stomach lie medial to the speen. these organs would not prevent the spleen from descending inferiorly.