I have come across something a bit confusing in the literature. In some papers the zones of cartilage are referred to as superficial, middle, deep and calcified; whereas in others they are referred to as superficial, transitional, middle or radial and calcified. Does this mean that in some cases the terms middle, deep and radial are interchangeable?
Personally, I would stick to superficial, middle, deep and calcified. Others have used tangential (superficial) transitional (middle) radial (deep) and calcified but in my experience these terms are much less common. Hope that helps.
Helen x
The terminology is not chisled in stone on this one. I would agree to Helens definition, naming the layers with theit position in the cartilage.. Terms like " radial" or "columnar" are more descriptive of their function.. I guess it also depends on if you talk abot articular or growth plate, in the latter, terms like "transitional" and "hypertrophic" are frewuemtly used as well...
I would say that the designation of the (articular) cartilage zones depends on the context. The zones are distinguished by the structure, biomechanical and other characteristics. In particular, if the differences in the fibrous structure are meant, the terms “tangential”, “isotropic”, and “radial” have been often used. Whereas superficial, transitional, deep, and calcified rather depict the morphologic characteristic, i.e. proteoglycan or water content, chondrocyte density etc.
Dear Jasmine!
There are basically four distinct zones in articular cartilage as follows
[Note: Please focus on the synonymous term]:
1. Superficial zone
2. Transitional zone
3. Middle/ Radial/ Deep zone
[Note: Some authors may further divide this zone into middle and deep zone]
4. Calcified cartilage zone
Reference:
Buckwalter, J.A. and Mankin, H.J. (1998). Articular cartilage: tissue design and chondrocyte-matrix interactions. Instr Course Lect, 47, 477-86.
Hope it helps!
It is difificult to seperate the histological from the biomechanical when discussing cartilage. As a non-heterogeneous material consisting of superficial (10-20%), middle (40-60%), deep (30%), and a thin calcified bottom layers. Each layer has specific mechanical properties and is identified by distinct variations in the size and direction of collagen fibers. The proteoglycan content is lowest in the superficial zone and increases with depth. The middle zone of cartilage has more loosely packed collagen fibers, giving it the highest Young’s modulus of compressive. It is these variations in tissue morphology which account for the tensile and shear resistant properties of cartilage.