One in 20 of us are born with an extra one of these. What is it?

CrazeeTracy

Rib http://thebestof.wetpaint.com/page/Random+Facts?t=anon Nov 12 07, 7:32 AM

McGruff

This needs a reference other than a factoid page that simply says: "One in every 20 people is born with an extra rib." If it is indeed true, we need to find something citing a medical study or something similar. Nov 12 07, 10:15 AM

warriorone

An extra set of ribs. http://www.enotes.com/nursing-encyclopedia/skeletal-system A pair of ribs extends forward from each of the 12 thoracic vertebrae, for a total of 24 ribs. Occasionally, a person is born with an extra set of ribs. The joint between the ribs and vertebrae is a gliding (or plane) joint, a type of synovial joint, as ribs do move, expanding and contracting with breathing. Most of the ribs (the first seven pair) attach in the front of the body via cartilage to the long, flat breastbone, or sternum. These ribs are called true ribs. The next three pair of ribs are false ribs. False ribs attach to another rib in front instead of the sternum, and are connected by cartilage. The lower two pair of ribs which do not attach anteriorly are called floating ribs. Ribs give shape to the chest and support and protect the body's major organs, such as the heart and lungs. The rib cage also provides attachment points for connective tissue, to help hold organs in place. In adult humans, the sternum also produces red blood cells as well as providing an attachment site for ribs. Nov 12 07, 12:44 PM

McGruff

I found the same information, word for word, here: http://science.jrank.org/pages/6159/Skeletal-System-Axial-skeleton.html What I'm wondering about is the frequency, what exactly do they mean by "occasionally". "One in 20" is quite often, but most references say humans have 12 sets of ribs. They don't say "humans have 12, or sometimes 13 sets of ribs," which would be more correct if one in every 20 people had 13 sets of ribs. One extra rib appears to be more common, but still does not occur anywhere near one in every 20 people. "A cervical rib is a supernumerary (extra) rib which arises from the seventh cervical vertebra. It is a congenital abnormality located above the normal first rib. A cervical rib is present in only about 1 in 200 (0.5%) of people; in even rarer cases, an individual may have not one but two cervical ribs. The presence of a cervical rib can cause a form of thoracic outlet syndrome due to compression of the brachial plexus or subclavian artery." http://en.wikipedia.org/wiki/Cervical_rib I think it's a faulty factoid. Perhaps it was a typo of "one in 200" and has been copied incorrectly since then. Nov 12 07, 11:18 PM