1. VEINS ASSOCIATED WITH HEART
Dr. Mujahid Khan

2. Development of Veins
Three paired veins drain into the tubular heart of a four week old embryo
Vitelline veins return poorly oxygenated blood from the yolk sac
Umbilical veins carry well-oxygenated blood from the primordial placenta
Common cardinal veins return poorly oxygenated blood from the body of the embryo

4. Vitelline Veins
The vitelline veins follow the yolk stalk into the embryo
Yolk stalk is a narrow tube connecting the yolk sac with the midgut
After passing through the septum transversum the vitelline veins enter the venous end of the heart, the sinus venosus

7. Vitelline Veins
As the liver primordium grows into the septum transversum, the hepatic cords anastomose around preexisting endothelium-lined spaces
These spaces, the primordia of the hepatic sinusoids later become linked to the vitelline veins
The hepatic veins form from the remains of the right vitelline vein in the region of the developing liver
The portal vein develops from an anastomotic network formed by the vitelline veins around the duodenum

9. Umbilical Veins
The umbilical veins run on each side of the liver and carry well-oxygenated blood from the placenta to the sinus venosus
As the liver develops the umbilical veins lose their connection with the heart and empty into the liver
The right umbilical vein disappears during the 7th week
Now the left umbilical vein is the only vessel carrying well-oxygenated blood from the placenta to the embryo

11. Umbilical Veins
The right umbilical vein and the caudal part of the left umbilical vein between the liver and the sinus venosus degenerate
The persistent caudal part of the left umbilical vein becomes the umbilical vein
It carries all the blood from the placenta to the embryo

13. Umbilical Veins
A large venous shunt, the ductus venosus develops within the liver and connects the umbilical vein with the inferior vena cava
The ductus venosus forms a bypass through the liver
This enables most of the blood from the placenta to pass directly to the heart without passing through the capillary networks in the liver

14. Cardinal Veins
The cardinal veins constitute the main venous drainage system of the embryo
The anterior and posterior cardinal veins drain cranial and caudal parts of the embryo
The anterior and posterior cardinal veins join the common cardinal veins which enter the sinus venosus

17. Cardinal Veins
During the eighth week the anterior cardinal veins become connected by an anastomosis
This anastomosis shunts blood from the left to the right anterior cardinal vein
This shunt becomes the left brachiocephalic vein when the caudal part of the left anterior cardinal vein degenerates
Superior vena cava forms from the right anterior cardinal vein and the right common cardinal vein

20. Posterior Cardinal Veins
The posterior cardinal veins develop primarily as the vessels of the mesonephroi and largely disappear with these transitory kidneys
The only adult derivatives of the posterior cardinal veins are the root of the azygos vein and the common iliac veins

22. Subcardinal & Supracardinal Veins
The subcardinal and supracardinal veins gradually replace and supplement the posterior cardinal veins
The subcardinal veins appear first
They are connected with each other through the subcardinal anastomosis and with the posterior cardinal veins through the mesonephric sinusoids
The subcardinal veins form the stem of the left renal veins, suprarenal veins, gonadal veins and a segment of IVC

24. Subcardinal & Supracardinal Veins
The supracardinal veins are the last pair of vessels to develop
They become disrupted in the region of the kidneys
Cranial to this they become united by an anastomosis that is represented in the adult by azygos and hemiazygos veins
Caudal to the kidneys the left supracardinal vein degenerates
The right supracardinal vein becomes the inferior part of the IVC

26. Inferior Vena Cava
The inferior vena cava forms during a series of changes in the primordial veins of the trunk
This occurs as blood returning from the caudal part of the embryo is shifted from the left to the right side of the body
The IVC is composed of four main segments

28. Inferior Vena Cava
A hepatic segment derived from the hepatic vein (proximal part of right vitelline vein) and hepatic sinusoids
A prerenal segment derived from the right subcardinal vein
A renal segment derived from the subcardinal supracardinal anastomosis
A postrenal segment derived from the right supracardinal vein