Fetal Circulation | Angiology | Anjani Mishra

 Written by Anjani Mishra

Fetal circulation

• The source of oxygenated blood is the placenta.

• Oxygenated blood from placenta come to the fetus through the umbilical vein, which joins the left branch of the portal vein.

• A small portion of this blood passes through the substance of the liver to the caudal venacava, but the greater part passes direct to the caudal venacava through the ductus venosus. A spincter mechanism in the ductus venoses controls blood flow.

• The oxygen rich blood reaching the right atrium through the caudal venacava is directed by the valve of the caudal venacava towards the foramen ovale.

• Most of the blood from the right atrium passes into the left atrium through foramen ovale. Rest of the blood get mixed up with the blood returning to the right atrium through cranial venacava and passes into the right ventricle.

• From the right ventricle, the blood (mostly deoxygenated ) enters the pulmonary trunk. Only a small portion of this blood reaches the lungs. The major portion reaches into the brachiocephalic trunk through ductus arteriosus.

• The left atrium receives oxygenated blood from the right atrium and small amount of deoxygenated blood from lungs.

• The blood in this chamber is therefore, fairly rich in oxygen. This blood passes into the left ventricle and then into the ascending aorta.

• From left ventricle through ascending aorta, some of this oxygen rich blood passes into subclavian and carotid arteries to supply the brain, head, neck and forelimb. The rest of it gets mixed up with poorly oxygenated blood from the ductus arteriosus.

• The parts of the body that are supplied by the branches of aorta arising distal to the junction of the ductus arteriosus and therefore receives blood with moderate oxygen content.

• Much of the blood carried out by descending aorta supplies to the different parts of the body. The deoxygenated blood from different parts of the body is carried out by umbilical arteries to the placenta for oxygenation.

Fig: Fetal circulation

Changes that takes place after birth

1. Umbilical vein- umbilical ligament
2. Umbilical artery- round ligament of urinary bladder
3. Ductus venoses – ligamentum venosum
4. Ductus arteriosus ligamentum arteriosum
5. Foramen ovale- fossa ovale

Hepato- portal circulation

The term portal system is often applied to the portal vein and its tributaries, which come from the stomach, intestine, pancreas and spleen. The vein enters the liver, where it branches like an artery, so that the blood in this subsidiary system passes through a second set of capillaries (in the liver) before conveyed to the heart by the hepatic veins and the caudal venacava.

                                               Fig: Hepato-portal circulation

Formation 

• Two mesenteric (cranial and caudal) veins join with the right and left ruminal veins to form the portal vein.

• Right ruminal vein is formed by the union of right ruminal vein proper, splenic and pancreatic veins, while the left ruminal vein is formed by the union of left ruminal, reticular and omaso-abomasal veins.

• The veins from the jejunum and ileum join to form cranial mesenteric vein and those of different parts of colon unite to form the caudal mesenteric vein.

• The portal vein then passes forward below the abdominal venacava (caudal venacava) and enters the liver at the portal fissure, close to the entry of hepatic artery.

If you have any questions you can ask me on :

mishravetanatomy@gmail.com 

Facebook Veterinary group

link -  https://www.facebook.com/groups/1287264324797711/ 

Twitter - @MishraVet

Facebook - Anjani Mishra

Website: mishravetanatomy.blogspot.com