The Apple Inc. executive in charge of product design for the iPhone and smartwatch is stepping down, bringing a shake-up to the company’s most critical product lines.

Tang Tan, whose title is vice president of product design, is leaving in February, according to people with knowledge of the matter, who asked not to be identified because the move isn’t public. Tan reports to John Ternus, senior vice president of hardware engineering, and the division is reshuffling duties to handle the transition.

Several deputies to Ternus and Tan are getting expanded roles as part of the changes. That includes Richard Dinh, Tan’s top lieutenant and head of iPhone product design. Dinh is being elevated to report directly to Ternus. Kate Bergeron, a hardware engineering executive responsible for Mac teams, is taking over the design of the Apple Watch.

Apple didn’t respond to a request for comment on the changes.

The iPhone and Apple Watch are central to Apple’s operations, accounting for well over half of the tech giant’s US$383.3 billion in revenue last year. Tan also was responsible for the design of accessories and oversaw the company’s acoustics team, which handles much of the development of the AirPods. Those two groups are being relocated under Matthew Costello, who is in charge of Beats and the HomePod smart speaker.

People familiar with Apple’s operations say the Tan departure is a blow, and that he made critical decisions about Apple’s most important products. Beyond the iPhone, his work on the Watch and AirPods helped turn those devices into major growth drivers for the Cupertino, California-based company.

Under Apple’s organizational structure, the product design team works closely with its industrial design and operations groups. Tan’s team has tight control over product features, including the look of devices and how they’re engineered.

Tan is the second senior executive to announce departure plans recently. Bloomberg News reported earlier this week that Steve Hotelling — a vice president in charge of hardware technologies like Touch ID, Face ID and displays — is retiring. Hotelling reported to Johny Srouji, senior vice president of hardware technologies.

It’s also at least the third exit in a year from Ternus’ organization. Yannick Bertolus, who was once in charge of hardware product quality and later ran hardware product management, recently retired. His predecessor in the latter role, Laura Legros, left at the end of last year.

Ternus, who took charge of hardware engineering in 2021, recently shuffled other parts of the organization. He elevated Dan West — formerly the No. 2 executive for hardware quality — to a new non-product role reporting to him. Other executives in charge of Mac product design and iPhone hardware systems were also promoted, suggesting that Apple could be preparing for more leadership changes in the coming year.