ABSTRACT
Anatomy and function of the thymus e thymus gland is a bilobed so tissue organ that extends from the level of the fourth costal cartilage in the chest inferiorly up to the basis of the neck superiorly, sometimes as high as the lower border of the thyroid gland or even higher23Figures 37.1 through 37.4. Lateral borders of the thymus are in direct contact with the pleura. e upper part of the trachea, anterior surface of the heart, and vessels of the superior mediastinum (le brachiocephalic vein, aortic arch, and pulmonary artery) are located along the posterior border of
the thymus. e anterior surface of the thymus is covered by manubrium sterni and origins of the sternohyoid and sternothyroid muscles (Figure 37.3). e upper pole of the le lobe usually extends higher to the neck region than the upper pole of the right lobe (Figure 37.1). Conversely, the lower end of the
Figure 37.3 Anatomic specimen of the sagittal section of the fetal thorax. Note extension of the thymus from anterior surface of the heart in the chest inferiorly to the basis of the neck superiorly. Left brachiocephalic vein and trachea can be identified along posterior border of the thymus. (LBCV, left brachiocephalic vein; St, sternum; Tr, trachea.)
Figure 37.1 Anatomic specimen of the fetal thorax viewed from the front. Note the location of the thymus in the mediastinum and its relationship to the heart, lungs, and trachea.
