The Temperature Field of the Body Core

Abstract

For many aspects of temperature regulation, it is sufficient to treat the temperature of the body core as a uniform entity. However, it is a simplification. The temperature of an organ, and, in fact, of any site within it, depends on the temperature of the arterial blood flowing into the organ, local heat production and local rate of blood flow. The organs of the body differ in the two last factors, and so do local temperatures, leading to passive thermal gradients within the body. In humans resting in a thermoneutral environment, more than 70% of the heat is produced in the brain, heart, liver and kidneys, whose combined fraction of total body mass is just 8% [11]. These organs are warmer than the remainder of the inner body. Apart from a single modelling study in humans [531], no systematic data are available concerning the temperature distribution in animals. However, it is presumably safe to assume that under normal conditions, that is, rest in thermoneutrality, the mean temperature of any organ in the inner body does not deviate by more than 0.4 °C from arterial blood temperature as the reference. Intraorgan differences can be larger [188], and the temperature of the fetal lamb was reported to exceed, in late pregnancy, that of the ewe by 0.7 °C [299].