Zum Ossifikationsprinzip des Schildknorpels
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The principle of ossification of the thyroid cartilage
In the final analysis, the aetiology of the ossification of the human thyroid cartilage is still not clear. The two halves of the thyroid cartilage obtained from 94 corpses of both sexes having an age range of 15–79 years, were subjected to an X-ray examination. The ossified area was investigated morphometrically with the aid of the Leitz-Texture Analysis System, and evaluated statistically. In addition, the state of deformation in the plane during swallowing was investigated in both nonossified and ossified thyroid cartilages, using wire strain gauges. Ossification begins at the lateral and caudal edges at the age of about 16, reaches a maximum at about age 50, and then remains constant for the rest of life. There is no difference between the sexes except for the fact that ossification occurs some 3 years later in the female, and is less marked. The process of ossification occurs, to varying degrees, predominantly in four directions. It is most marked in the direction parallel to the caudal edge, and is less marked along the vertical line connecting the superior and the inferior cornua, vertically at the thyroid notch, and in the diagonal direction extending from latero-caudal to medio-cranial. The greatest extension occurs parallel to the caudal edge, to a lesser extent in the three other directions, and decreases from lateral to medial. Ossification occurs preferentially along the lines of maximum extension of the muscles attached to the thyroid cartilage. This stiffening of bone prevents the deformation of the cartilage during the act of swallowing, and is an example of the self-regulating adaptation of the connective and supportive tissue to mechanical stressing. On account of the different
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