Parathyroid Glands

The usual text description of the parathyroid glands hold true in only about 25% of cases studied; their number and location is highly variable. They may be located within the thorax embedded in thymic tissue, in the posterior mediastinum, and in the areolar tissue associated with the pericardium. In one study of 86 glands, 76 were found dorsal to the thyroid gland, one at the ventrocaudal pole and nine caudal to it. Of the latter nine, four were in contact with the thyroid capsule and five were found in the loose connective tissue ventral and lateral to the trachea, or in the tissue extending from the thyroid capsule to the thymus. Of the 76 glands found on the dorsum of the thyroid, six were associated with the cranial third of the the thyroid, and the remainder were distributed over the caudal two-thirds with a concentration near the cricoid cartilage and first tracheal ring. Exceptional locations were as follows: between the isthmus of the thyroid and trachea, one case; in the triangular cleft formed by the thyroid, trachea, and esophagus, three cases; and near the midline between esophagus and trachea, one case. In one study of 25 larynges, 86 glands were found (average 3.2 per specimen). The number per specimen varied from two to six. The glands were distributed as follows: 7% were opposite the cranial third of the thyroid, 57% opposite the middle third, 25.6% opposite the caudal third, and 10.4% caudal to the thyroid. One gland was found (partly) on the ventral surface of the thyroid. None was found embedded in the thyroid glandular tissue.

The parathyroids were studied by gross dissection supplemented by microscopic inspection in twenty-five human specimens. A total of eighty-six definite parathyroid glands was found, making an average of 3.2 per specimen.

It is suggested by Heinbach (1933) that the customary nomenclature, according to which, "there are two pairs of parathyroids, superior and inferior," with a typical location for each pair, is misleading, since no investigator, who has carefully studied and analyzed a series of cases, has found exactly four parathyroids in much more than 50 per cent of the specimens, and since in many cases where four have been found, there is a great variation.

Table 1

Parathyroids in Man

Number of parathyroids

Number of cases

Percentage

2

5

20%

3

10

40%

4

6

24%

5

2

8%

6

2

8%

A comparison of the number of parathyroid glands per specimen found by the author, with the findings of other investigators, is shown in table 2:

Table 2

Authors

Number of cases

Average number per case

Berkeley ('09)

125

2.5

Pool ('16)

16

2.9

Geis ('18)

12

3.0

MacCallum ('16)

64

3.2

Heinbach ('33)

25

3.2

Yanase ('28)

89

3.3

The parathyroid glands may be located on the anterior surface of the thyroid gland. A parathyroid gland was found on the anterior surface of the thyroid isthmus. In a study of 42 larynges, 30 glands were identified, of which 35.9% were found on the ventrolateral thyroid capsule and 9.5% on the ventral thyroid capsule. An accessory parathyroid was found carried by the vagus nerve. Based on the studies cited above it is clear that the number of parathyroid glands vary in number. In addition, there may be numerous minute glands scattered in the connective tissue near the usual location.

Based on the above studies it is clear that the number of parathyroid glands vary in number. In addition, there may be numerous minute glands scattered in the connective tissue near their usual location.

Number and Location of Parathyroid Glands (1 - 12)

Number and Location of Parathyroid Glands (13 - 24)

Number and Location of Parathyroid Glands (25 and 26)

Riferimenti dell’opera originale

Elenco riportato come compare nella fonte, senza normalizzazione dei formati bibliografici.

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• Bérard, L. et H. Alamartine. (1909) Les parathyroides externes de l'homme. Soc. Biol. Comptes Rendus Hebdomadaires des Séances et Mémoires 66:619-621.
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