Abdomen: Where It Starts, Where It Ends, and Why Insects Have One Too
The abdomen is the part of the body between the chest and the pelvis, holding the stomach, liver and intestines. In insects and spiders it is the rear section of three.
In humans, the abdomen is the region between the diaphragm and the pelvis — what most people simply call the belly. It contains the stomach, liver, spleen, pancreas, kidneys and most of the intestines, held in place by a muscular wall rather than by bone.
That absence of bone is the point. The ribcage protects the chest; the abdomen has to protect itself with muscle, which is why abdominal injuries are serious and why the word turns up so often in medicine.
The main senses
- The human belly region. *The pain was in the lower right abdomen.*
- The same region in other mammals. *The vet shaved the dog's abdomen.*
- The rear body section of an insect or spider. After the head and thorax.
Word forms
| Form | Word | Example |
|---|---|---|
| Noun (singular) | abdomen | He felt a dull ache in the abdomen. |
| Noun (plural) | abdomens | The abdomens of the two species differ. |
| Adjective | abdominal | Abdominal surgery, abdominal muscles. |
| Informal short form | abs | Sit-ups work the abs. |
How it is used in a sentence
- The scan showed fluid in the abdomen.Standard clinical use.
- A bee's abdomen carries the sting at its tip.The insect sense.
- She was training her abdominal muscles six days a week.The adjective is far more common in everyday speech than the noun.
- Doctors divide the abdomen into four quadrants to describe where pain is.A practical convention rather than an anatomical boundary.
The four quadrants
| Quadrant | Mainly contains |
|---|---|
| Upper right | Liver, gallbladder |
| Upper left | Stomach, spleen |
| Lower right | Appendix, part of the small intestine |
| Lower left | Descending colon |
This is why a doctor asking *where exactly does it hurt* is not stalling. Pain in the lower right quadrant suggests something very different from pain in the upper left.
Where the word comes from
Straight from Latin *abdomen*, meaning the belly or paunch, which was already an anatomical term in Roman medical writing. Its earlier history is uncertain; one old suggestion links it to *abdere*, to hide away, on the idea that the organs are concealed there, but that connection is not proven.
Is the abdomen the same as the stomach?
No, and this is the most common mix-up in English. The stomach is one organ inside the abdomen. When people say they have a stomach ache they usually mean abdominal pain.
Where does the abdomen begin and end?
It runs from the diaphragm, just under the ribs, down to the top of the pelvis. Anatomists often treat the abdomen and pelvis together as the abdominopelvic cavity.
Why do insects have an abdomen?
Insect bodies have three parts: head, thorax and abdomen. The abdomen holds the digestive and reproductive organs and, in bees and wasps, the sting.