Which uterine layer is most responsive to the hormone oxytocin, which increases contractions and leads to expulsion of the fetus?

The answer is Myometrium. Myometrium is a center muscular layer of uterus; constitutes most of uterine wall; and more fibrous near cervix; produces labor contractions, expels fetus) composed mainly of smooth muscle (sweep downward from fundus, spiral around body; less muscular. oxytocin promotes labor by directly stimulating muscles of myometrium; stimulating fetal membranes to produce prostaglandins, which are synergists of oxytocin in producing labor contractions.