Kaiser Permanente is one step closer to completing its major build-out of new medical clinics in the Mid-Atlantic region with the opening this week of a multispecialty hub Largo, its fifth since 2011.

The Largo facility, at 1221 Mercantile Lane, includes a 24-hour urgent care and observation unit, an ambulatory surgery center, radiology, pharmacy and other lab services, and several medical specialities. It is larger than, but similar to, Kaiser clinics that have opened in NoMa, Tysons Corner, Gaithersburg and Baltimore in recent years.

Each facility is designed to treat Kaiser’s members for all illnesses, injuries and diseases short of those that require more than 24 hours in a hospital. The clinics are crucial to Kaiser’s plans to increase its membership without buying or building a costly inpatient hospital.

Only about half of the Largo building’s eventual 233,000 square feet of medical space opened this week; the remainder is slated for completion in 2014.