The third, termed the corpus spongiosum (spongy entire body), is a tube that lies centrally beneath the many others and expands at the finish to type the suggestion of the penis (glans). The shaft and glans have no muscle mass fibers. The lifted rim at the border of the shaft and glans is named the corona. On days fifteen to 28-the article-ovulatory phase, the Graafian follicle-now termed the corpus luteum-secretes estrogen.