What is Rugae?

Mary McMahon
Mary McMahon

In anatomy, “rugae” is a term which refers to the ridges formed by tissue which is naturally folded. Rugae can be found in a number of anatomical structures in the body. The arrangement of the folds can vary from person to person, causing the ridges to look different in different people. Folds in body tissue serve a number of important functions, ranging from protecting reproductive ability to ensuring that someone can eat comfortably.

An illustration of a human stomach, which creates gastric rugae when empty.
An illustration of a human stomach, which creates gastric rugae when empty.

One of the most famous sets of rugae is the gastric rugae found on the inside of the stomach. The stomach is an organ which must be able to expand and contract, sometimes relatively rapidly, to accommodate people at mealtimes and as they digest. No tissue is elastic enough on its own to accommodate the needs of the stomach. As a result, the stomach is designed to be folded and wrinkled when it is empty so that it will take up less space, creating the gastric rugae.

The hard palate of the mouth contains rugae.
The hard palate of the mouth contains rugae.

When someone eats, the stomach unfolds to accommodate the meal. The stomach can unfold just enough to make room for the food and as the food moves through the stomach, it shrinks back down. The gastric rugae can be seen when a doctor performs an endoscopy to look inside the stomach to learn more about health problems someone is experiencing. Certain surgeries may also involve exposure of the folds inside the stomach.

The vagina contains rugae, allowing it to expand and contract.
The vagina contains rugae, allowing it to expand and contract.

As one might expect from the explanation about rugae in the stomach, other organs which need to be able to expand and contract have similar folds. The gallbladder and urinary bladder are both wrinkled when they are empty, expanding and flattening out as they fill up. The back of the hard palate also has a series of ridges created by folds.

The gastric rugae can be seen when a doctor performs an endoscopy to look inside the stomach.
The gastric rugae can be seen when a doctor performs an endoscopy to look inside the stomach.

Folds can also be seen in the genitals. The vagina has a series of rugae which allow it to expand and contract, perhaps most notably for the purpose of delivering a baby. The scrotum is also covered in a series of folded ridges which facilitate the regulation of temperature in the testes. Sperm are very sensitive to temperature changes and as a result the testes retract in cold weather to take advantage of body heat, while they drop into the scrotum in hot weather to move them away from the body and to allow the large wrinkled surface area of the scrotum to keep them cool and prevent overheating.

The scrotum is covered in a series of folded ridges which regulate the temperature in the testes.
The scrotum is covered in a series of folded ridges which regulate the temperature in the testes.
The stomach is designed to be folded and wrinkled when it is empty so that it will take up less space.
The stomach is designed to be folded and wrinkled when it is empty so that it will take up less space.
The back of the hard palate has a series of ridges created by folds.
The back of the hard palate has a series of ridges created by folds.
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments

anon1000951

If there is a problem in gastric rugae function, is the absorption of food be affected or nutrients are not absorb properly?

Acracadabra

@yumdelish - My friend had gastric bypass surgery and she cannot eat very much at one time anymore. I would assume that this means the rugae area of her stomach have been reduced.

Perhaps it is possible to stretch other organs, such as the bladder, but I doubt it would be a permanent thing. The primary purpose of rugae is to allow this part of the body to shrink and grow many times.

yumdelish

Is it possible that you can do permanent damage to a rugae's function? Say you don't go to the bathroom often enough and your bladder spends a lot of time expanded, could it be stretched forever?

Potterspop

I would like to say a big thank you for this article. I came across the word in a crossword, and tried to find a clear explanation in a medical dictionary. Needless to say I was not enlightened, but the information here was easy to understand.

It's amazing to read about how the stomach rugae expands after eating, and definitely explains why I get that horrible bloated feeling after an extra large meal.

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