Anatomy study note · Thorax

Thymus

A flat, bilobed lymphoid organ between the sternum and the pericardium in the anterior mediastinum, where T lymphocytes develop.

Key points

• Anterior (and superior) mediastinum, behind the sternum.
• Largest relative size at birth; involutes after puberty.
• Site of T-lymphocyte development.
• Thymus: 3rd pharyngeal pouch endoderm.
• Cortex: T-cell maturation, blood–thymus barrier.
• Medulla: Hassall corpuscles.

The full note in the atlas also covers

Features · Blood supply · Histology · Development

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Written from

• Snell’s Clinical Anatomy by Regions, 10th ed., ch. 5, PDF p. 662
• Inderbir Singh’s Human Embryology, ch. 9, PDF pp. 120, 128
• BRS Cell Biology & Histology, 7th ed., ch. 12, PDF pp. 224–226

More from the thorax

• Trachea
• Tricuspid valve
• Vagus nerve
• Aortic valve
• Arch of aorta
• Ascending aorta
• Azygos vein
• Brachiocephalic artery
• Brachiocephalic veins
• Bronchopulmonary segments
• Coronary sinus and cardiac veins
• Costal cartilages

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