Thoracic ducts, Azygos and hemi Azygos.pptx

Anatomy note

1. Final pathway of lymphatics ( T he Thoracic D uct )

2. Introduction The lymphatic system serves as a slow flowing, low pressure drainage system That collects a small portion of the interstitial fluid ( ISF, lymph ) from throughout the body Returns it to the bloodstream.

3. What actually is the lymph? Lymph is the fluid that circulates throughout the lymphatic system . The lymph is formed when the interstitial fluid (the fluid which lies in the interstices of all body tissues) is collected through lymph capillaries . It is then transported through lymph vessels to lymph nodes Before emptying ultimately into the right or the left subclavian vein , where it mixes back with blood.

4. Composition of lymph Since the lymph is derived from the interstitial fluid, its composition continually changes as the blood and the surrounding cells continually exchange substances with the interstitial fluid. It is generally similar to blood plasma except that it also contains white blood cells . Lymph returns proteins and excess interstitial fluid to the bloodstream. Lymph may pick up bacteria and bring them to lymph nodes where they are destroyed. Metastatic cancer cells can also be transported via lymph. Lymph also transports fats from the digestive system.

5. Composition contd. Lymph has a composition comparable to that of blood plasma , but it may differ slightly. Lymph contains white blood cells . In particular the lymph that leaves a lymph node is richer in lymphocytes . Likewise, the lymph formed in the human digestive system called chyle is rich in triglycerides (fat), and looks milky white.

6. Composition contd. Another useful way to view the composition of lymph is that it is similar to blood without the red blood cells . That is not a technically precise definition, but it is a good first-order approximation.

7. Lymph in a test tube

8. Formation of lymph Blood supplies nutrients and important metabolites to the cells of a tissue It collects back the waste products they produce, which requires exchange of respective constituents between the blood and tissue cells. However, this exchange is not direct but instead is effected through an intermediary called interstitial fluid or tissue fluid that the blood forms. Interstitial fluid is the fluid that occupies the spaces between the cells and constitutes their immediate environment.

9. Formation of lymph contd. Interstitial fluid forms at the arterial (coming from the heart) end of capillaries because of the higher pressure of blood compared to veins , and most of it returns to its venous ends and venules the rest (up to 10%) enters the lymph capillaries as lymph. Thus, lymph when formed is a watery clear liquid with the same composition as the interstitial fluid. However, as it flows through the lymph nodes it comes in contact with blood, and tends to accumulate more cells (particularly, lymphocytes) and proteins.

10. The thoracic duct Lymph flows slowly along the primary lymphatics, the lymph empties into progressively larger lymphatic vessels which ultimately converge as the Thoracic Duct The thoracic duct finally empties its contents into the right and left subclavian veins in the thorax.

11. Formation of the thoracic duct At the level the 2 nd lumber vertebra anteriorly , an enlarged sac is formed by unification of small lymphatics. This enlarged sac is called Cistern Chyli The Thoracic Duct arises anterior to the second lumbar vertebra from this enlarged sac, the cistern chyli .

12. cisterna chyli The thoracic duct beginning as the cisterna chyli . This sac like lymphatic mass collects lymph from lower limbs of the body as well as the digestive system.

13. Thoracic duct

14. Features of lymphatic system Unlike the circulatory systems, the lymphatic system lacks any central "heart“- like organ to pump lymph throughout the lymph vessels. Instead, the lymphatic system depends on muscular movement, breathing, and simple gravity to move lymph fluid throughout the body.

15. Features of lymphatic system contd. The Thoracic Duct contains smooth muscle. The muscle is the same type that exists in the lower digestive system and the arterial system This is necessary in order to aid lymph flow. Thus, frequent movement is critical for humans to properly move lymph and prevent lymph fluid build-up in certain areas of the body. ( lymph-oedema )

16. Eponyms of thoracic duct In human anatomy , the thoracic duct is the largest lymphatic vessel of the lymphatic system . It is also known as the left lymphatic duct , alimentary duct , chyliferous duct , and Van Hoorne's canal . It carries chyle , a liquid containing both lymph and emulsified fats, rather than pure lymph . Thus when it ruptures, the resulting flood of liquid into the pleural cavity is known as chylothorax .

17. Volume / size In adults, the thoracic duct is typically 38–45 cm in length H as an average diameter of about 5 mm. The vessel usually starts from the level of the twelfth thoracic vertebrae (T12) and extends to the root of the neck . It drains into the systemic (blood) circulation at the left subclavian vein. It also collects most of the lymph in the body other than from the right thorax, arm, head and neck which are drained by the right lymphatic duct . [1]

18. Course of Thoracic duct The lymph duct originates in the abdomen from the confluence of the right and left lumbar trunks and the intestinal trunk , forming a significant pathway upward called the cisterna chyli . It traverses the diaphragm at the aortic aperture It ascends the superior and posterior mediastinum between the descending thoracic aorta (to its left) and the azygos vein (to its right).

19. Termination of the thoracic duct The duct extends vertically in the chest Curves posteriorly to the left carotid artery and left internal jugular vein at the T5 vertebral level to It empty into the junction of the left subclavian vein and left jugular vein , below the clavicle , near the shoulders .

20. Special features / transport mechanism The lymph transport, in the thoracic duct, is mainly caused by the action of breathing , aided by the duct's smooth muscle and by internal valves which prevent the lymph from flowing back down again. There are also two valves at the junction of the duct with the left subclavian vein, This is to prevent the flow of venous blood into the duct. In adults, the thoracic duct transports up to 4 L of lymph per day.

21. Clinical importance (Index of Malignancy) The first sign of a malignancy, especially an intra-abdominal one, may be an enlarged Supraclavicular lymph node. This is known as Virchow's node , a lymph node in the left supra-clavicular area, This is found in the vicinity where the thoracic duct empties into the left innominate vein , This is between where the left subclavian vein and left internal jugular join. This junction is known as the left Pirogoff angle .

22. chylothorax When the thoracic duct is blocked or damaged A large amount of lymph can quickly accumulate in the pleural cavity , This situation is called chylothorax

23. Azygos &Hemi Azygos vein Azygos means 'unpaired', and hemi means half The name for hemi- azygos vein is derived from that of the azygos vein .. This vein mirrors the bottom half the Azygos vein.

24. Azygos & Hemi-Azygos Veins

25. Azygos and Hemi Azygos veins The hemiazygos vein and the accessory hemiazygos vein , when taken together, essentially serve as the left-sided equivalent of the azygos vein . That is, the azygos vein serves to drain most of the posterior intercostal veins on the right side of the body, While the hemiazygos vein and the accessory hemiazygos vein drain most of the posterior intercostal veins on the left side of the body. Specifically, the hemiazygos vein is a mirror image of the bottom part of the Azygos vein.

26. Variation in formation The structure of the hemiazygos vein is often variable. It usually begins in the left ascending lumbar vein or renal vein , and passes upward through the left crus of the diaphragm to enter the thorax . It continues ascending on the left side of the vertebral column , and around the level of the ninth thoracic vertebra , it passes rightward across the column, behind the aorta , esophagus , and thoracic duct , to end in the azygos vein .

27. Variation in formation contd. The hemiazygos may or may not be continuous superiorly with the accessory hemiazygos vein . It receives the 9th, 10th, and 11th posterior intercostal veins and the subcostal vein of the left side, and some esophageal and mediastinal veins.