Can you explain the different pathways for FDA approval or clearance of medical devices, such as the premarket approval (PMA) process for high-risk devices and the 510(k) clearance process for moderate-risk devices? How does the FDA assess the safety and effectiveness of medical devices through premarket review, postmarket surveillance, and quality system regulations? Furthermore, what are the implications of FDA regulation for medical device manufacturers, healthcare providers, and patients in terms of patient safety, innovation, and market access?