FOETAL CIRCULATION By Sri Utpal Das Mahadevananda Mahavidyalaya

FOETAL CIRCULATION(ভরণ র স বহন ) By Sri Utpal Das Mahadevananda Mahavidyalaya Department of Physiology (For 2 nd Semester Students) PHYGCOR 02 T

The Foetus: It is the term to refer to a prenatal (জনম র আগ ) mammal between its embryonic state (ভরণ য পরয য ) and its birth. The Placenta (অমর ) : The placenta is a temporary organ that connects the developing fetus via the umbilical cord to the uterine wall to allow nutrient uptake, thermo-regulation, waste elimination, and gas exchange via the mother's blood supply; It fights against internal infection and to produce hormones which support pregnancy. (Wikipedia)

The Umbilical Cord(ন ভ র করড ): A flexible (নমন য )cord-like structure containg blood vessels (রকত জ ল ক ) and attaching a human to the placenta. It is responsible for the supply and elimination of CO 2 and O 2.

Foetal circulation: The circulation of oxygenated blood , deoxygenated blood, nutritive material etc in the foetus is termed as “Foetal Circulation” (Diagram: from Wikipedia)

Role of Placenta in Foetal circulation: The circulatory system of the mother is not directly connected to that of the foetus. So the placenta functions as thr Respiratory Centre(শবসন ক নদর ) for the foetus. It becomes a site of Filtration (পর সর বণ ) for plasma nutrients and wastes. Foetal Lungs: Pulmonary vascular resistance (ফসফস য জ ল ক ����� ব ধ দ ন ) is the resistance offered to blood through lungs. The resistance(ব ধ দ ন ) is very high in foetus. Because of this high pressure, the blood is diverted from Pulmonary Artery into Aorta. Diagram: http: //www. fetalultrasound. com/online/text/3084. htm

Blood Vessels in Foetus: The following blood vessels are responsible for Foetal Circulation: 1. Umbilical Vein 2. Umbilical Artery Diagram From https: //www. open. edu/openlearncreate/mod/

Umbilical Vein: a) It carries Oxygenated blood from the placenta to the growing foetus. b) The blood pressure inside the umbilical vein is approx 20 mm. Hg. Diagram from: https: //concordneonatal. com/cordclampi ng/

2. Umbilical Artery The umbilical arteries supply deoxygenated blood from the fetus to the placenta. (Although this blood is typically referred to as deoxygenated, it is important to note that this blood is fetal systemic arterial blood and will have the same amount of oxygen and nutrients as blood distributed to the other fetal tissues. ) There are usually two umbilical arteries present together with one umbilical vein in the umbilical cord. The umbilical arteries surround the urinary bladder and then carry all the deoxygenated blood out of the fetus through the umbilical cord. Inside the placenta, the umbilical arteries connect with each other at a distance of approximately 5 mm from the cord insertion in what is called the Hyrtl anastomosis.

Shunts Involved in the Foetus: There are three (3) shunts present in a fetous: i) Ductus Venosus: It shunts t 6 he portion of left umbilical vein blood flow directly to the : inferior vena cava. ii) Ductus Arteriosus Also called Ductus Botalli. It connects the pulmonary artery to the proximal Discending Aorta. It allows most of the blood from the right ventricle to bypass the foetus fluid filled non functioning lungs. iii) Foramen Ovale

Foramen Ovale: It is an opening in the intra-arterial septum. It allows the blood to enter the left atrium from the right atrium. It is also called False Septi. https: //www. pinterest. com/pin/86272149092064389/

Pecuilarities of Foetal Circulation: 1. Parallel arrangements of two main arterial systems and their respective ventricles. 2. High resistance and low flow of pulmonary circulation 3. Low resistance and high flow of placental circulation 4. presence of Shunts 5. From Umbillical vein blood enters liver of fetous and some amount bypasses liver and enters IVC (Inferior Vena Cava) through ductus venous. 6. IVC drains into RA(Right Atrium) 7. 50% of blood from RA enters LA through Foramen Ovale. 8. Another 50% enters RV( Right Ventricle) from there into pulmonary artery. But fetal lungs are collapsed. 9. To avoid of collapse of the fetal lungs, only small amount of blood reaches LA(Left Auricle) through pulmonary veins.

10. The main bulk of blood from RV (Right ventricle) enters aorta through Ductus Arteriosus. 11. Blood from aorta is then distributed to the whole body. 12. Two umbillical arteries which arise from fetal aorta transport blood to placenta for oxygenation.

https: //www. docsity. com/en/flow-chart-of-fetalcirculation-cardiology-lecture-slides

https: //www. docsity. com/en/flow-chart-of-fetal-circulation-cardiology-lecture-slides/

Changes Occuring at birth: i)Closure of umbilical veins ii) Closure of Ductus Venosus iii) Expansion of Lungs iv) As lungs fill with air, pulmonary vascular resitance decreases v) Closure of Foramen Ovale cause of change inpressure gradient between atrias.

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