Dr. Reynolds announced her plan to become a doctor when she was 8, inspired in part by her pediatrician. “We moved a lot in my childhood — I went to 10 schools before I graduated high school — and there was a good bit of chaos, but somehow my mother managed to take me to see him over many years,” she said. “Almost no one in my family had gone to college, and his was a powerful example of an important, concrete job that I could understand.”

She went to Columbia University as a pre-med student on a full scholarship, and trained as an emergency medical technician on an ambulance in Chinatown “because it seemed more like the real world.” But she got hooked on the school’s mandatory Great Books program. “Literature, history, philosophy — books I’d never been exposed to growing up,” she said. “I was just blown away by what I was learning, and when I got the chance to stay for graduate school on a fellowship, I did.” She earned a doctorate in literature, but the desire to become a physician never left.

She attended the University of California, San Francisco, School of Medicine, where she was drawn to emergency medicine. “What I loved best was having one foot in the world and one in the hospital — the process of moving from a patient’s account to a diagnosis, having to build a relationship quickly.”

In 2010, she described that experience in the London-based New Left Review. “I spent my early childhood in a trailer” in Texas, she wrote, “so, until I became an emergency physician in Oakland, I thought I knew something about barriers to health care access, and maybe even something about poverty.” Residency training at a public county hospital taught her, she said recently, about how social context affects illness, about how to work creatively with whatever is at hand, and about the enormous range of human experience, even in a wealthy country like the United States.

“I first met Teri early in her medical career, when she was starting her emergency medicine residency in California in a gritty, inner-city hospital,” said Michael Callaham, professor emeritus of emergency medicine at the San Francisco medical school, who was her supervisor during that time and when she was a resident fellow with the Annals of Emergency Medicine, and gave her her first faculty job. “It’s not often you get a medical trainee with a Ph.D. in English literature,” said Dr. Callaham, who remains the scientific journal’s editor in chief.

Dr. Reynolds said that women were still outnumbered in emergency medical care globally, but that that was slowly changing. “I still sit in many meetings around the world where there are few women at the table and none at the head,” she said. But the W.H.O. has put many women in the top positions, and for the first time recently, the majority of its assistant directors general are women. The gender distribution “will impact the tone around the world,” she said. “There are many young women emerging into leadership in the field, and I can’t wait to see what they do.”