This diagram exemplifies the position of the arteries in the epithelium of the uterus. The straight arteries are so named because of their shape, and they lie in the mucosa, and terminate in the spiral arteries which are alo in the mucosa and so named because of their shape . The spiral arteries run in the stratum functionalis, the straight arteries run in the stratum basalis.
At the time of menstruation the spiral arteries and the stratum functionalis ar shed
Artistically the straight arteries and and spiral arteries are personified to look like people. The blue background creates the effect of a blue sky on a summer day, and hence the name -“taking a walk on a summer day”.