Modern healthcare systems face an escalating challenge: patients are living longer, presenting with greater complexity, and requiring care that spans multiple clinical domains simultaneously. The traditional model of siloed, specialty-specific care is increasingly inadequate to address the interconnected realities of chronic disease, mental health comorbidity, and acute crisis. This study explores the conceptual and practical foundations of a unified multidisciplinary framework that integrates lifelong primary care, emergency response capacity, and mental health support into a coherent model of patient-centered care. Drawing on current evidence across primary care implementation, surge capacity planning, psychiatric-medical comorbidity management, lifestyle medicine, and multidisciplinary team models, this review argues that meaningful improvements in patient outcomes are only achievable when these domains are treated not as parallel systems but as mutually reinforcing components of a single, adaptive care continuum. Key themes include the role of health equity in primary care delivery, the critical importance of mental health integration, the operational demands of hospital surge response, and the evidence supporting structured multidisciplinary collaboration. The study concludes with a proposed framework for operationalizing this integration at both the institutional and system levels.