Which tool is primarily used to listen to a patient's internal sounds?

The stethoscope is the primary tool used to listen to a patient's internal sounds, such as the heartbeat, lung sounds, and bowel sounds. This instrument amplifies the sounds produced by the body, allowing healthcare professionals to assess various physiological functions while providing them with important information about a patient's health status.

In contrast, a sphygmomanometer is specifically designed for measuring blood pressure, while a thermometer is used to check body temperature. A microscope is utilized for examining small samples at a much higher magnification, typically in laboratory settings. Each of these tools serves a distinct purpose within the healthcare field, but only the stethoscope is used for directly listening to and evaluating the internal sounds of the body.