Organs of the Thorax

The organs of the thorax include the thymus gland, the breasts, the heart, the lungs, the tracheobronchial tree and the pleurae.

The thymus gland is located in the superior mediastinum of the thoracic cavity but may also extend into the neck. It is classified as a lymphoid organ, meaning that it plays a role in the development of the immune system. Following puberty, the thymus gland undergoes involution meaning that it shrinks in size and will eventually be replaced by fat.

The breasts are paired structures located in the pectoral region of both males and females. In females, however, mammary glands are present which serve an important role in lactation. It is important to understand the lymphatic drainage of breast tissue as breast cancer cells are able to use the lymphatic system as a means of metastasis.

The heart is a major organ in the thorax and is situated in the middle mediastinumof the thoracic cavity and is associated with many great vessels. The heart contains four chambers and the wall of the heart itself is made up of 3 separate layers. The right side of the heart pumps blood into the pulmonary circulation whilst the left side of the heart pumps blood into the systemic circulation. The 4 valves of the heart ensure that blood only flows in one direction. The heart has its own arterial supply and venous drainage systems and is surrounded by a fluid-filled sack called the pericardium to protect it from damage.


The tracheobronchial tree is made up of the trachea, bronchi and bronchioles and allows air to pass into the lungs. The lungs act as major respiratory organs as they bring deoxygenated blood from the heart and inspired air into close contact, meaning that gas exchange can occur efficiently. Surrounding the lungs and thoracic cavity are the pleurae,which are two-part serous membranes that ensure effective respiration.

In this section, learn more about the anatomy of the organs of the thorax– thymus gland, the breasts, the heart, the lungs, the tracheobronchial tree and the pleurae.


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The Thymus Gland

The Breasts

The Heart

  • The Valves of the Heart
  • The Chambers of the Heart
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The Lungs

The Tracheobronchial Tree

The Pleurae



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