What Is an Epiphyseal Line?
The epiphyseal line the part of the bone that replaces the epiphyseal growth plate in long bones once a person has reached their full adult height. Either rounded end of a long bone is called an epiphysis, and the shaft of the bone is called the diaphysis. The epiphyseal line is the marking that indicates where the two parts of the bone meet and where the epiphyseal plate was once located in children and young adults.
An epiphyseal line is visible on a standard x-ray. It looks like a thin dark streak that stretches horizontally across the rounded ends of the bone. The line may be slightly raised and rougher than the surrounding bone. A person with abnormal bone growth may have a visible crack or an uneven line showing on an x-ray.
Formation of this line takes place over many years. When the growth rate slows down after puberty, the cells stop the process of replication and all bone growth eventually stops. Ossification, the hardening of cells into bone, of the epiphyseal plate occurs when osteoblasts transform the cartilage cells found in the growth plate into bone. Once the entire growth plate is ossified, the epiphyseal line has formed.
The epiphyseal plate is the portion of the bone that is responsible for a bone’s growth in length. It is formed from cartilage cells that are constantly dividing within the growth plate. As the new cells get older, they begin to ossify, or harden, and become part of the bone. Bone growth occurs when the layers of ossified cells build up in size.
Injuries to the epiphyseal plate may cause abnormal bone growth. This may cause early formation of the epiphyseal line and an end to longitudinal bone growth in the affected limb. Fractures that pass through the epiphyseal plate may need to be stabilized with the surgical placement of pins and plates. These may allow the delicate cartilage growth plate to heal and restore the normal pattern of bone growth.
The presence of an epiphyseal line on the long bones can be used to indicate the age of skeletal remains. Only fully grown adults will show evidence of the formation of bone marking. Bones that are not marked with the line can be reasonably determined to belong to an individual that is still growing.
This shows one of the reasons it's so important that children and young adults don't smoke. Smoking can affect bone growth quite a lot, and it will, for example, slow down healing time for broken bones. It just stops enough oxygen getting to where it is needed.
So if a young person is smoking while their bones are still growing at the epiphyseal growth plate, they could be permanently weakening them, something they may come to regret later in life. The bones are fragile enough without subjecting them to more stress.
@browncoat - It's not just relevant to crimes and things like that. I'm sure they use it to compile data on ancient bones as well.
Like Egyptian mummies for example. People back then were quite a bit smaller than we are now, but I'm sure the bone structures were similar in terms of age and when the epiphyseal line would have formed.
So they would be able to tell, for example, that Tutankhamun the "boy-pharaoh" died when he was only 18 years old.
If they went by the size of the mummy alone they might have thought he died when he was much younger.
I imagine this is one of the ways in which they determine how old a person was when they died. I'm not sure if it would help after the person reached a certain age and the line was already formed though.
Like, for example if they find old bones from an accidental death or murder in a forest or a lake or something, they would be able to make a guess as to how old the person was when they died.
As a person who has very tall relatives, I can tell you that the size of a bone is not always going to be the best indication of the age of the person. I have a nephew who looks about the height of an eight year old, but he's only five at the moment.
I think this kind of criminology and forensic science is really interesting.
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