Potential space between sternum & pericardium.
Overlapped by anterior edges of both lungs.
Continuous with pretracheal space of neck through superior mediastinum (\ infections in pretracheal space ¨ anterior mediastinitis).
Contents: i) thymus, ii) sternopericardial ligaments, iii) lymph nodes, iv) branches of internal thoracics.
Bilobed organ. Most prominent in children, running from lower pole of thyroid ¨ 4th CC. Lies behind pretracheal fascia, long straps & manubrium/sternum.
- behind is pericardium, arch of aorta, L brachiocephalic, trachea
Different colour to fat: pinker or browner, lobules larger/smoother/denser. Pretracheal fascia is key to exposure of thymus; gland is dissected from its posterior surface.
From inferior thyroid and internal thoracic arteries & corresponding veins.
- a large short thymic vein may enter the L brachiocephalic
No afferent channels. Drains into parasternal, tracheobronchial & brachiocephalic nodes.
From epithelium of 3rd pouch; same one as inferior parathyroids. Epithelial cells ¨ (1) thymic (HassallŐs) corpuscles and (2) reticular cells ?concerned with T cell differentiation.
- as everywhere, surrounding mesoderm supplies connective tissue elements
- colonising lymphocytes come from bone marrow.
Access: via median sternotomy.