What is the difference between using a mercury thermometer orally and rectally?

The differences between using a mercury thermometer for oral and rectal temperature measurements lie in the measurement site, thermometer design, and normal temperature ranges. The specific analysis is as follows:

1. Measurement Site

When measuring oral temperature with a mercury thermometer, the thermometer is placed in the mouth; whereas for rectal temperature measurement, it is inserted into the lower end of the rectum.

2. Thermometer Design

For oral temperature measurement, the mercury bulb of the thermometer is typically slender, allowing the mercury to absorb heat and expand quickly within the mouth to display a reading. For rectal use, the mercury bulb is usually round-shaped to help prevent injury to the anal mucosa during measurement.

3. Temperature Ranges

The normal oral temperature range is generally 36.3°C to 37.2°C, while the normal rectal temperature range is approximately 36.9°C to 37.9°C.

Body temperature can be measured not only orally and rectally but also under the armpit. Temperature readings may be influenced by various factors such as emotions, physical activity, and environmental conditions.