MadSci Network: Anatomy

Re: how do lipids function as an isulator in human bodys?

Date: Tue Jan 18 15:54:45 2005
Posted By: Debra Lowe, Secondary School Teacher, Bio/Zoo, Jordan School District
Area of science: Anatomy
ID: 1104705560.An

Hi Sam,

Wow, those are an interesting series of questions. Let me see if I can clarify this for you. The basic idea that you are asking about is insulation. Whether on a house, in a human, or in nature, insulation involves the basic idea of trapping heat. Heat travels very poorly through certain materials, so these materials become a shield between the user and the (typically) cold world.

Insulation can be artificial or natural. You’ve mentioned blubber as a natural insulator, and it is, but human fat does not fit in this category. If humans primarily used fat as insulation, the average body temperature of a super-model would be much less than that of a sumo, but all human temperatures are within a couple degrees of 98.6º Fahrenheit ( or 32ishº Celcius).

Before getting into human temperature regulation, you should probably know that there are two types of human fat; brown and white/ Brown fat is most common in infants. This fat actually generates heat due to its mitochondria. Brown fat keeps infants warmer than they would be otherwise. It also seems to be prevalent in hibernating animals. Adult humans don’t have this type of fat.

The more common type of fat is white fat, which is actually more of a cream color. It is also known as adipose tissue. This is the fat that cushions people’s organs, serves as food storage, and adds unsightly bulges that dieters are always trying fight. This fat doesn’t have a large number of blood vessels and therefore is tough to lose. Multiple factors seem to dictate how much of this fat a person has. This fat is very poor at regulating temperature for a variety of reasons.

Human skin, which is outside of the fat layer, has a large amount of blood vessels in it. The blood gives off heat to the environment, doing away with any insulating effects the fat layer may have. Our skin, nervous system and endocrine (hormone) systems have much more control in temperature regulation than our layer of fat. Shivering, sweating, and the ability to walk out of the cold into a warmer environment are far more useful to humans.

Most human temperature regulation is controlled by the nervous system. The brain and nerves cause blood vessels to constrict or dilate, changing the amount of blood flowing to the skin. More blood flow means that more heat is lost. Less blood flow means that heat is conserved.

Temperature regulation is also influenced by the endocrine system. Certain glands, such as the thyroid and hypothalmus help regulate body temperature, but these must work within boundaries. If the temperature gets too high, it can start to cook the body from the inside out. This is why high fevers must be controlled. If temperature is too low, the body starts to shut down. This is called hypothermia.

Clothing was also an item of interest to you. Do humans really need clothing? The human body can keep its temperature regulated (even without protective coverings) very nicely in tropical climates. You only have to go as far as a National Geographic to show that clothing in some regions is optional. But humans travel far in search of food or space. To live in cooler climates, people have to maintain body temperature somehow. Clothing is the natural answer. Humans don’t need clothing to survive in the tropics, but we certainly find them useful in temperate or polar regions.

Clothing traps a layer of air inside it. This air is warmed by body heat. If the clothing is thick, it takes longer for the warm air to escape, which is why wool feels warmer on a cold day than cotton. Fur traps heat inside it the same way; by putting air in contact with skin temperatures, warming the air and trapping it at the same time. Some materials trap air better than others. A layer of plastic can also trap heat inside, even though it’s quite thin, while even a thick layer of mesh doesn’t do as good of a job.

Hope this satisfies some of that curiosity. Best wishes.

Picture and information from:
Georgia State University: ml
Information also from:
Encyclopædia Britannica: http://www.b
The Townsend Letter for Doctors and Patients: y/ai_104259134
And the Comenius University Medical School: http://nic.s

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