For most of his life, Russell M. Nelson has been touching people’s hearts.

He did so from the 1950s to the mid-1980s with a scalpel in his hand. In the more than three decades since, he has done so through sermons in his soul.

The 93-year-old Nelson, a cardiothoracic-surgeon-turned-Mormon-apostle, is poised to become the 17th president of the nearly 16 million-member Church of Jesus Christ of Latter-day Saints.

Through unfailing tradition, Nelson, as the faith’s longest-tenured apostle, is expected to be set apart in the coming days as the successor to the late Thomas S. Monson, who died Tuesday night at 10:01 p.m. at his Salt Lake City home.

Nelson would be the second-oldest apostle to assume the presidency in Mormon history. Joseph Fielding Smith, the church’s 10th prophet, was a few months older at the time he took the post.

After Monson’s Jan. 12 funeral, it is expected that the remaining Mormon apostles, with Nelson presiding, will assemble and select the next church president, who then will choose two counselors to assist him in a new governing First Presidency.

“Throughout the history of the church, the longest-serving apostle has always become the president of the church when the First Presidency has been reorganized,” the church noted on its website.

Nelson became next in line to guide the Utah-based faith when he was set apart July 15, 2015, to replace the late Boyd K. Packer as president of the Quorum of the Twelve Apostles.

Russell Marion Nelson was born Sept. 9, 1924, in Salt Lake City, to Marion C. and Edna Anderson Nelson.

The budding heart surgeon grew up loathing liver. Whenever his mother served it, he waited until she looked away and then crammed the offensive meat into his pocket.

“This maneuver was a little hard on pockets, but it was, nevertheless, very successful,” Nelson said in Spencer Condie’s 2003 biography, “Russell M. Nelson, Father, Surgeon, Apostle.”

He also played football — at least officially. A biography on the LDS Church’s website notes that Nelson suited up with his high school team but the surgeon-to-be “didn’t want his hands to get stepped on.” So the coach relegated him to the bench. Nelson later used those hands to perform surgery on his ex-coach.

During high school, he formed a love for biology and math.

“And I loved people,” he told a University of Utah Dean’s Roundtable discussion in 2014. “I told Mom and Dad, ‘I don’t want to disappoint you, but I want to be a doctor.’ ”

So Nelson set off toward that goal. He earned his medical degree, with highest honors, at the U. in 1947 and was part of a research team that developed the heart-lung machine that made possible the first human open-heart surgery in 1951.

He spent two years as an Army medical officer during the Korean War, serving in Korea and Japan and at Walter Reed Army Medical Center in Washington. After the conflict, Nelson received additional surgical training at Harvard Medical School’s Massachusetts General Hospital in Boston.

In 1955, he returned to Utah to accept a faculty post at his alma mater, the U.’s medical school, where he conducted the state’s first open-heart surgery.

Nelson had delved into heart studies at a time when few medical experts undertook such work.

“When we were in medical school, we were taught that one must never touch the beating heart,” Nelson recalled during an alumni event in 2015 at the U. “If you touched it, it would stop beating.”

The young physician would go on to touch many hearts — physically and spiritually.

Among his later cardiac patients was then-LDS Church President Spencer W. Kimball, who received an aortic valve replacement in 1972.

Nelson shared his medical skills and knowledge across the globe. In 1980, he trained heart surgeons at three universities in China, and it was there, in 1985, that he performed his last open-heart surgery.

He and his first wife, Dantzel White Nelson, raised 10 children — nine daughters and one son — before her death in 2005. Nelson remarried in 2006, making Wendy L. Watson, an author and church speaker in her own right, his wife.

After serving in various ward- and stake-level leadership positions, Nelson became the church’s general president for Sunday school programs in 1971 and then was called as a regional church representative in 1979.

In 1984, Nelson was elevated to the apostleship at age 59. The next year, he led the church’s Eastern European operations, helping to expand the faith’s presence in the former Soviet bloc nations.

In all, according to Condie’s book, Nelson has visited 110 nations as a Mormon representative, flying not only to European locales but also Central Asia and China — using his fluency in Mandarin in the latter case to strengthen ties between the American and Chinese medical communities.

As a senior apostle, Nelson has increasingly urged Mormons to resist challenges to the faith’s core beliefs and evolving policies.

In a January 2016 sermon to Mormon millennials, he defended the church’s then-new stance that labels same-sex LDS couples as “apostates” and generally forbids their children from baptism and other religious rites until they turn 18.

Nelson declared that the policy represented “the mind of the Lord and the will of the Lord” as revealed to Monson, the faith’s prophet.

He urged his young audience members to stay true to the faith and defend it against critics.

“The somber reality is that there are ‘servants of Satan’ embedded throughout society,” he said. “So be very careful about whose counsel you follow.”

The safest course, Nelson advised, is to heed the words of top Mormon leaders.

“Prophets see ahead. They see the harrowing dangers the adversary has placed, or will yet place, in our path,” he said. “Prophets also foresee the grand possibilities and privileges awaiting those who listen with the intent to obey.

“ ... You may not always understand every declaration of a living prophet,” he added. “But when you know a prophet is a prophet, you can approach the Lord in humility and faith and ask for your own witness about whatever his prophet has proclaimed.”

Nelson again stressed the theme of holding to the faith’s teachings — despite the widening chasm between popular cultural and LDS beliefs — during his April 2017 General Conference address.

“True disciples of Christ are willing to stand out, speak up, and be different from the people of the world,” he said. “They are undaunted, devoted and courageous.”

In October 2015, during his first General Conference speech after taking the helm of the Quorum of the Twelve Apostles, Nelson challenged Mormon women to “speak up and speak out” during leadership meetings in their LDS congregations and in their homes.

His push came amid a continuing debate about the role of women inside the LDS Church. Some are calling for female ordination to the all-male Mormon priesthood; others are seeking more visibility in the higher echelons and a greater voice in key decisions.

“We need your impressions, your insights and your inspiration. We need you to speak up and speak out in ward and stake councils. We need each married sister to speak as a ‘contributing and full partner’ as you unite with your husband in governing your family,” he told LDS women throughout the world. “Married or single, you sisters possess distinctive capabilities and special intuition you have received as gifts from God. We brethren cannot duplicate your unique influence.”

And few can match Nelson’s unique resume — internationally acclaimed heart surgeon and now the principal leader of a growing global faith.

Dallin H. Oaks, a former Utah Supreme Court justice and an LDS apostle for nearly 34 years, is next in line for the presidency after Nelson. Oaks is 85.

Reporter Peggy Fletcher Stack contributed to this story.

Correction, Jan. 3, 12:05 a.m.•. If Russell M. Nelson becomes the next LDS Church president, he would be the second-oldest apostle to assume that post. One of the earlier versions of this story misstated that point.