What is the term for observing internal structures and functions of the body without surgery?

The correct answer is diagnostic imaging. This term encompasses various techniques used to visualize the internal structures and functions of the body non-invasively. Methods such as X-rays, MRI (Magnetic Resonance Imaging), CT scans (Computed Tomography), and ultrasound are all forms of diagnostic imaging that allow healthcare professionals to observe internal organs, tissues, and systems without the need for surgical intervention.

While radiology refers broadly to the field that encompasses these imaging techniques, diagnostic imaging specifically refers to the actual process of using these technologies to assess and diagnose medical conditions. Endoscopy, on the other hand, does involve the insertion of a flexible tube with a camera to visualize the interior of a hollow organ or cavity, making it a minimally invasive procedure rather than a completely non-invasive one. A biopsy involves taking a sample of tissue for further examination, which also requires a degree of surgical procedure, thus not falling under the definition of non-surgical observation.