I stumbled upon this YouTube video while checking other things and wanted to share. It explains the importance of the latissimus dorsi in yoga:
The TL;DR text version — The latissimus dorsi is the only muscle that connects the hips and the arms. This is relevant in various postures where the hips are moving in one direction while the arms move in another, such as chair pose (with the hips moving down while the arms reach up) or down dog (with the hips lifting up while the arms press down).
My core take on things: A lot of shit is tied up in the hips. In terms of chakras, the hips and sacrum are home to svadisthana, the seat of emotion. In more physical terms, the hips are a crossroads where the spine meets the legs and where various unneeded bodily substances (urine, feces, menstrual blood) are held and then eliminated. The hips are also the lower attachment point for a lot of the core muscles — all of the abdominals, some of the back muscles, and the entire pelvic floor. Anything that inhibits movement in the hips, including tight lats, has the potential to impact the entire core.