The human body is an incredibly complex and intricate system, with various processes and mechanisms working to keep us alive and functioning. Among these is the regulation of body temperature, which allows us to maintain a consistent internal temperature despite changes in our external environment.
Body Temperature Regulation
Human body temperature is not uniform throughout the entire body and certain areas tend to be warmer than others. The hypothalamus, a small structure located in the brain, is the body’s thermostat and works to keep our core internal temperature within a narrow range around 98.6°F (37°C). This process of thermoregulation involves balancing heat production and heat loss.
When our cores become too hot, the hypothalamus initiates various mechanisms to cool us down, like sweating and dilation of blood vessels close to the surface of the skin. When we get too cold, it conserves heat by triggering shivering and constriction of surface blood vessels. Factors like age, gender, time of day, hormones, metabolism, and environmental conditions all impact normal body temperature.
Measuring Body Temperature
While 98.6°F (37°C) is considered normal, the actual core body temperature averages closer to 97.7°F (36.5°C) for healthy adults. Typical oral temperature, which is easier to measure than core, ranges from 97.6–99.6°F (36.4–37.6°C).
Doctors use various methods to measure body temperature:
- Oral temperature, taken by placing a thermometer in the mouth under the tongue
- Rectal temperature, taken by inserting a thermometer a short distance into the rectum
- Ear (tympanic) temperature, taken by placing a thermometer in the ear canal
- Temporal artery temperature, taken by running a scanner across the forehead
- Axillary temperature, taken under the armpit
While each site provides slightly different readings, rectal temperature provides the most accurate measurement of core body temperature.
Average Temperature by Body Part
Now that we understand how body temperature works, what are the hottest areas of the human body? While the hypothalamus regulates a set point to maintain ideal core body temperature, certain body parts tend to run warmer than others. Here are average surface temperatures by location:
| Body Part | Average Temperature (°F) |
|---|---|
| Forehead | 90.5 |
| Nose | 90.0 |
| Ears | 97.6 |
| Cheeks | 88.1 |
| Hands | 82.4 |
| Limbs (arms/legs) | 85.1 |
| Feet | 78.8 |
As you can see, the ears tend to be the warmest surface area on the exterior of the body. The ears don’t have sweat glands and the cartilage tissue doesn’t easily dissipate heat, causing them to be significantly warmer than other exposed body parts.
Why Are Ears So Warm?
There are a few reasons why ears are warmer than other external areas of the body:
- Lack of sweat glands – Sweat cools the body through evaporation but ears don’t contain sweat glands
- Thin skin – Ears have thin skin with less fat beneath the surface to provide insulation
- Cartilage doesn’t cool well – The external structure is composed of cartilage which doesn’t cool down easily
- Dense network of blood vessels – Arteries and veins run throughout the ear to supply nerves and tissues
The combination of these anatomical factors causes the ears to more readily radiate body heat compared to other exterior regions. Even on cold days, ears tend to stay nice and toasty.
Hottest Internal Body Parts
While the exterior surface of ears is the hottest area of the skin, the absolutely hottest places in the human body exist inside. Exact temperatures are difficult to measure, but we can look at average readings from internal organs:
| Body Part | Average Core Temperature (°F) |
|---|---|
| Heart | 99.5 |
| Brain | 100.4 |
| Liver | 101.0 |
| Spleen | 102.2 |
Here we see that internal organs run significantly hotter than external body parts, with the liver reaching temperatures over 100°F (37.8°C).
Why Are Internal Organs So Hot?
Some reasons why core organs maintain such high temperatures include:
- Constant blood flow – Organs require a steady supply of warm, oxygenated blood to function
- Metabolic activity – Active tissues like the liver and brain generate more cellular heat
- Insulation – Internal locations are shielded from external cooling factors
- Proximity to heat sources – Organs are located near major blood vessels and warm abdominal cavity
Protection within the abdomen coupled with crucial operations that require energy and blood flow leads to very stable yet elevated temperatures in core organs.
The Hottest Spot: Brown Fat in Infants
Newborn infants are unable to efficiently regulate their body temperature and depend on a specialized type of fat tissue called brown adipose tissue (brown fat) to generate heat and keep warm. Brown fat is packed with blood vessels and mitochondria that can rapidily burn energy. In babies, concentrated areas of brown fat around the neck, chest, and upper back can reach temperatures up to 105°F (40.6°C) through a process called non-shivering thermogenesis.
While we tend to lose brown fat stores as we age, small amounts can persist into adulthood along the neck and spine. However, the high metabolic activity of concentrated brown fat in infants makes it the absolute hottest part of the human body.
Summary
To summarize, while the hypothalamus keeps core body temperature tightly controlled, some body parts tend to run warmer than others:
- The external ears have the hottest surface temperature, around 97.6°F.
- Internally, organs like the liver reach around 101°F due to metabolic activity.
- Concentrated deposits of brown fat in babies can spike up to 105°F.
So in the end, the hottest place in the human body is brown fat tissue in infants. Understanding patterns of body heat distribution can provide insight on temperature regulation and help detect abnormalities.