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Table 1 Diagrams and brief descriptions of the shapes identified for tracheal ring classification

From: Morphometric characterisation of human tracheas: focus on cartilaginous ring variation

Assigned code Tracheal ring shape Description of ring
A A singular band of tracheal cartilage resembling a ring throughout with parallel borders
B A straight band of tracheal cartilage on the left half of the ring, and a split into two distinct bands at the right end
C A straight band of tracheal cartilage on the right half of the ring, and a split into two distinct bands at the left end
D Two singular rings of tracheal cartilage connected by a band of cartilage directed infero-medially from the right end of the proximal ring
E Two singular rings of tracheal cartilage connected by a band of cartilage directed infero-medially from the left end of the proximal ring
F A thick ring of tracheal cartilage with two distinct bands on both right and left ends
G A thick ring of tracheal cartilage with a slit in the centre
H A band of tracheal cartilage that resembles an upright pentagon in shape with an apex in the centre of the superior border
I A band of tracheal cartilage that resembles an inverted pentagon in shape with an apex in the centre of the inferior border
J A triangular piece of cartilage on the left side that did not extend beyond the tracheal midline. Connective tissue occupied the rest of the layer
K A triangular piece of tracheal cartilage on the right side that did not extend beyond the tracheal midline. Connective tissue occupied the rest of the layer
L Other A ring shape which does not conform to the aforementioned descriptions or is a combination of one or more of the ring types