The thymus

10 The thymus



10.1 Can the thymus be felt?


Concealed and protected by the sternum, the thymus is impossible to palpate. It lies against the upper surface of the heart, at the root of the great vessels, in the anterior mediastinum.



10.2 Anatomy review


The thymus is situated in front of the brachiocephalic vein and the superior vena cava (Fig. 10.1). It is surrounded on either side by folds of pleura.


image

Fig. 10.1 Location of the thymus.


At the level of the sternal angle (second costosternal junction) it forms the thymic triangle whose apex is directed caudally.



10.2.1 Evolution


In the newborn, the thymus weighs about 10 g. By puberty, at 40 g, it has reached its maximum development (Fig. 10.2).


image

Fig. 10.2 Evolution of the thymus.


The thymus has two lobes which normally extend superiorly to the lower edge of the thyroid gland and in the adult can migrate inferiorly as far as the fourth intercostal space.


During dissections with Professor Arnaud, we have rarely seen the adult thymus present as anything more than small islands, imbedded in connective tissue. Professor Arnaud maintained that the gland evolves into a ligament of the heart, reinforcing the pericardium. As a result it is impossible to gauge its weight in the adult. Because of the numerous possibilities of involution, the thymus displays multiple morphological variations (Fig. 10.3).


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Fig. 10.3 Morphological variations of the thymus.

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Nov 7, 2016 | Posted by in MANUAL THERAPIST | Comments Off on The thymus

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