Both of these verses show events of Christ's life with which we are familiar. Our very familiarity may obscure a possible meaning that Nephi saw in this information. Remember that for Nephi these where future events, not part of almost two thousand years of tradition as they are with modern audiences. For Nephi, the import of these things was likely not simply a recitation of the life of the Savior, but a description of particular events which would have extra meaning to Nephi.
After the brief reference to twelve with its connotation of Israel, we have angels descending, and healings being performed. In the mythology associated with the Tree of Life, and with which Nephi would have been familiar, the Tree is a conduit between heaven and earth, and the source of the healing fruit (or liquid). When Nephi sees angels descending and Christ performing healings, the association of Christ and the Tree of Life is once again strengthened in Nephi's mind.