The azygos vein connects the inferior vena cava and the superior vena cava The thoracic duct is the largest lymph vessel that ultimately drains lymph from all parts of the body into the blood circulation We shall look at them one at a time

1. Dr. NDAYISABA CORNEILLE
CEO of CHG
MBChB,DCM,BCSIT,CCNA
Supported BY
AZYGOS,THORACIC
DUCT and PORTO-
SYSTEMIC
ANASTOMOSIS

2. Introduction
• The azygos vein connects the inferior vena
cava and the superior vena cava
• The thoracic duct is the largest lymph vessel
that ultimately drains lymph from all parts of
the body into the blood circulation
• We shall look at them one at a time
Dr Ndayisaba Corneille

3. The azygos veins
• Components:
– the main azygos vein,
– the inferior hemiazygos vein (hemiazygos),
– the superior hemiazygos vein (accessory hemiazygos)
• Areas of drainage:
– the posterior parts of the intercostal spaces,
– the posterior abdominal wall,
– the pericardium,
– the diaphragm,
– the bronchi,
– the esophagus
Dr Ndayisaba Corneille

4. Azygos veins (1)
Dr Ndayisaba Corneille

5. Azygos veins (2)
Dr Ndayisaba Corneille

6. Azygos vein
• Origin:
– The origin of this vein is variable
– It is often formed by the union of the right
ascending lumber vein and the right subcostal
vein
• Course:
– It ascends through the aortic opening in the
diaphragm (T12) in the right side of the aorta to
the level of the fifth thoracic vertebra
Dr Ndayisaba Corneille

7. Cont/…
– Here, it arches forward above the root of the right
lung to empty into the posterior surface of the
superior vena cava
• Branches/tributaries:
– The 8 lower intercostal veins
– The right superior intercostal vein
– The superior and inferior hemiazygos veins
– Mediastinal veins
Dr Ndayisaba Corneille

8. Inferior hemiazygos vein
• Origin:
– Often formed by the union of the left ascending
lumber vein and the left subcostal vein.
• Course:
– It ascends through the left crus of the diaphragm
– At about the level of the 8th thoracic vertebra, it
turns to the right and joins the azygos vein
Dr Ndayisaba Corneille

9. Cont/…
• Branches/tributaries:
– Some lower left intercostal veins
– Mediastinal veins
Superior hemiazygos vein
• This vein is formed by the union of the 4th to
8th intercostal veins
• It joins the azygos vein at the level of the 7th
thoracic vertebra
Dr Ndayisaba Corneille

10. The azygos system (1)
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11. Dr Ndayisaba Corneille

12. The azygos system (2)
Dr Ndayisaba Corneille

13. Clinical significance of the azygos
veins
• In obstruction of the superior and inferior
venae cavae, the azygos veins provide an
alternative pathway for the return of venous
blood to the right atrium of the heart.
• This is possible since these veins and their
tributaries connect the superior and inferior
venae cavae
Dr Ndayisaba Corneille

14. THORACIC DUCT

15. Thoracic duct
• Also called the left lymphatic duct
• Origin:
– Begins below in the abdomen as a dilated sac, the
cysterna chyli
• Course:
– It ascends through the aortic opening in the
diaphragm (T12) on the right side of the descending
aorta
Dr Ndayisaba Corneille

16. Cont/…
– It gradually crosses the median plane behind the
esophagus and reaches the left border of the
esophagus at the level of the lower border of T4
(sternal angle)
– It then runs upwards along the left edge of the
esophagus to enter the root of the neck
– Here, it bends laterally behind the carotid sheath
and infront of the vertebral vessels
Dr Ndayisaba Corneille

17. Cont/…
– It turns downwards infront of the left phrenic nerve
and crosses the subclavian artery to enter the
beginning of the left brachiocephalic vein (confluence
of the left internal jugular and left subclavian veins)
– At the root of the neck, the thoracic duct receives the
left jugular, subclavian, and bronchomediastinal
lymph trunks
– They may alternatively drain directly into the adjacent
large veins
Dr Ndayisaba Corneille

18. Course of the thoracic duct
Dr Ndayisaba Corneille

19. Areas of drainage
• The thoracic duct conveys to the blood all
lymph from:
– The lower limbs
– Pelvic cavity
– Abdominal cavity
– Left side of the thorax
– Left side of the head and neck
– Left arm
Dr Ndayisaba Corneille

20. Right lymphatic duct
• The right jugular, subclavian, and
bronchomediastinal trunks, which drain the right
side of the head and neck, the right upper limb,
and the right side of the thorax, respectively, may
join to form the right lymphatic duct
• This common duct, if present, is about ½ inch
(1.3cm) long and opens into the beginning of the
right brachiocephalic vein (confluence of right
internal jugular and right subclavian veins)
Dr Ndayisaba Corneille

21. Cont/…
• Alternatively, the trunks may open
independently into the great veins at the root
of the neck
Dr Ndayisaba Corneille

22. Azygos, thoracic duct, & their
areas of drainage
Dr Ndayisaba Corneille

23. Dr Ndayisaba Corneille

24. Thoracic duct on the cadaver
Dr Ndayisaba Corneille

25. Orders Of Lymphatic Vessels
• Lymph capillaries - smallest
lymph vessels, first to receive
lymph
• Lymphatic collecting vessels -
collect from lymph capillaries
• Lymph nodes - scattered along
collecting vessels
• Lymph trunks - collect lymph
from collecting vessels
• Lymph ducts - empty into veins
of the neck

26. Lymphatic Collecting Vessels
• Accompany blood vessels
• Composed of the same three tunics as blood
vessels
• Contain more valves than veins do
– helps direct the flow of blood
• Lymph propelled by:
– contraction of skeletal muscles
– pulse pressure of nearby arteries
– Tunica media of the lymph vessels
Dr Ndayisaba Corneille

27. Lymph Nodes
• Cleanse the lymph of pathogens
• Human body contains around 500
• Lymph nodes are organized in clusters

28. Microscopic Anatomy of a Lymph Node
• Fibrous capsule – surrounds
lymph nodes
• Trabeculae – connective tissue
strands
• Lymph vessels
– Afferent lymphatic vessels
– Efferent lymphatic vessels

29. Lymph Trunks
• Lymphatic collecting vessels
converge
• Five major lymph trunks
– Lumbar trunks
• Receives lymph from lower
limbs
– Intestinal trunk
• Receives chyle from
digestive organs
– Bronchomediastinal trunks
• Collects lymph from thoracic
viscera
– Subclavian trunks
• Receive lymph from upper
limbs and thoracic wall
– Jugular trunks
• Drain lymph from the head
and neck

30. Lymph Ducts
• Cisterna chyli - located at the union
of lumbar and intestinal trunks
• Thoracic duct - ascends along
vertebral bodies
– Empties into venous circulation
– Junction of left internal jugular
and left subclavian veins
– Drains three quarters of the
body
• Right lymphatic duct - empties into
right internal jugular and subclavian
veins

31. The Immune System
• Recognizes specific foreign molecules
• Destroys pathogens effectively
• Key cells – lymphocytes
• Also includes lymphoid tissue and lymphoid
organs
Dr Ndayisaba Corneille

32. PORTO-SYSTEMIC
ANASTOMOSIS

33. INTRODUCTION
• Porto-systemic anastomosis is also known as
portocaval anatomoses
• This occurs between the veins of the portal
circulation and those of the systemic circulation.
• It serves as a collateral communication between
the portal and systemic venous system.
• The importance of this anastomosis is to provide
alternative routes of circulation when there is
blockage in the liver or portal vein.
Dr Ndayisaba Corneille

34. Dr Ndayisaba Corneille

35. Porto-systemic anastomosis
i) The superior rectal vein drains into the portal
circulation and the inferior rectal vein drains into the
systemic circulation (inferior vena cava)
• The anastomosis between the superior and inferior
rectal vein is known as porto-systemic anastomosis
• Blockage of the portal vein in liver disease will cause
portal hypertension, hence portal blood will move
retrograde and enlarge the anastomoses between
the superior rectal and inferior rectal veins, thereby
causing varicosity (hemorrhoids or piles)
Dr Ndayisaba Corneille

36. Dr Ndayisaba Corneille

37. Cont/…
ii). Esophageal branches of the left gastric vein
(portal circulation) anastomose with esophageal
branches of the azygous vein (systemic
circulation)
• In portal hypertension as a result of liver disease,
blood will move retrograde and expand these
anastomoses to form varicosities (esophageal
varicosities).
• These varicosities usually rupture and result into
vomiting of blood (hematemesis)
Dr Ndayisaba Corneille

38. Dr Ndayisaba Corneille

39. Cont/…
iii) The right colic vein, the middle colic vein and
the left colic vein (portal circulation)
anastomose with the renal vein, suprarenal
vein, paravertebral vein and testicular or
ovarian veins which are found on the posterior
abdominal wall (systemic circulation)
• This is yet another portal-systemic
anastomosis
Dr Ndayisaba Corneille

40. Dr Ndayisaba Corneille

41. Cont/…
iv) The paraumblical veins, tributaries of the portal vein
(portal circulation) anastomose with superficial epigastric
vein on the anterior abdominal wall (systemic circulation)
• In portal hypertension as a result of liver disease, blood
will move retrograde towards the anterior abdominal wall
through the anastomosis
• Stagnation or slowing down of blood flow may result into
ascites (accumulation of fluid within the peritoneum).
• Veins on the anterior abdominal wall will be logged with
blood and cause a condition known as caput medusae.
• This condition can be used to diagnose liver disease
Dr Ndayisaba Corneille

42. Dr Ndayisaba Corneille

43. Dr Ndayisaba Corneille

44. CLINICAL SIGNIFICANCE
A portosystemic shunt is the diversion of portal blood into a
systemic vein without the blood passing through the liver.
This occurs naturally in developing fetus
This may be intrahepatic or extrahepatic, congenital or
acquired.
Extrahepatic occurs in congenital atresia of the portal vein
Intrahepatic results from a connection between the portal
venous system within the liver and either the hepatic veins or
inferior vena cava
Signs/Symptoms: tremors, epileptic seizures, weight loss,
bladder stones, vomitting
Dr Ndayisaba Corneille

45. Portal Hypertension
• This is increase in blood pressure in the veins of
the venous system
Cause: blockage in the veins of the liver due to
pathological condition such as cirrhosis and the
inability of the blood to flow through.
Signs/symptoms: varicose veins on the abdominal
wall called caput medusa, oesophageal varices,
enlargement of the spleen, accumulation of fluid in
the peritoneal cavity and bleeding in the GIT.
Dr Ndayisaba Corneille

46. END
Dr Ndayisaba Corneille
THANKS FOR LISTENING
By
DR NDAYISABA CORNEILLE
MBChB,DCM,BCSIT,CCNA
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