cavity
Meaning of cavity: Anatomy and dentistry use one word for opposite things: a normal hollow space, and a hole that has no business being there.
Definition of cavity
A cavity is a hollow space. In anatomy the word names the body's natural enclosed spaces, such as the chest and abdominal cavities that hold and cushion the organs, along with smaller hollows within the skull and bones. In dentistry it names something quite different: a hole eaten into the hard tissue of a tooth by decay.
What are the body cavities?
The trunk is divided into large compartments, most of them lined by a slippery double membrane that lets organs move against each other without friction.
| Cavity | Contains |
|---|---|
| Cranial and spinal | Brain and spinal cord, wrapped in their membranes |
| Pleural cavity, one on each side | A lung, within a thin film of lubricating fluid |
| Pericardial cavity | The heart |
| Peritoneal cavity | Stomach, intestines, liver, spleen |
| Pelvic cavity | Bladder, rectum, reproductive organs |
Smaller hollows carry the name too: the oral cavity, the nasal cavity, the air-filled sinuses within the facial bones, the marrow cavity running down the shaft of a long bone, and the fluid-filled space inside a joint.
How does a dental cavity form?
The disease is called dental caries; the cavity is the hole it leaves. Bacteria living in the film on tooth surfaces ferment sugars and starches into acid. The acid pulls mineral out of the enamel, and saliva, with its minerals and fluoride, puts some of it back. Decay begins when loss outpaces repair for long enough. Enamel damage is often painless. Once the softer dentin beneath is reached, progress is faster and the tooth becomes sensitive to cold and sweetness. If the decay reaches the pulp at the center, where the nerve and blood supply sit, pain becomes persistent and infection can spread into the bone around the root.
Does the word mean anything else?
Yes, and it is worth recognizing. On a chest scan, a cavity is an abnormal air-filled space left where lung tissue has been destroyed, seen in tuberculosis, some fungal infections, lung abscess and certain tumors. Radiologists call such a lesion cavitary, and it is a description of a hole in tissue rather than a normal compartment.
Used in a sentence
The dentist identified a small cavity during the routine examination.
Good to know
A body cavity and a dental cavity share only the general sense of a hollow space, since one is normal anatomy and the other is the hole left by tooth decay.
Word origin
Where “cavity” comes from
From Latin cavus, meaning hollow.