establishment of foeto placental circulation with applied importance

Establishment of foeto placental circulation with applied importance : 

Establishment of foeto placental circulation with applied importance Dr. Manimay Bandyopadhyay Associate Professor Department of Anatomy Calcutta National Medical College

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Human placenta is a disc shaped chorio deciduate organ, connecting fetus with the uterine wall of the mother. Main functions of placenta are : Gaseous and metabolic exchange between mother and fetus. Production of hormones

Full term Placenta : 

Full term Placenta Diameter 15 – 25 cm Thickness 3cm Weight 500-600 gm Maternal side 15 – 20 cotyledons Fetal side chorionic plate

Primary villus : 

Primary villus Central core of cytotrophoblast surrounded by syncytiotrophoblast Secondary villus Syncytiotrophoblast + cytotrophoblast + extra embryonic mesoderm Tertiary villus Syncytiotrophoblast + cytotrophoblast + extra embryonic mesoderm + fetal blood vessels

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End of 2nd month – no chorion laeve End of 3rd month – ch laeve & decidua parietalis had fused

Placental Membrane(from fetal side) : 

Placental Membrane(from fetal side) The endothelium of fetal blood vessels with basement membrane. Surrounding mesoderm Cytotrophoblast Syncytiotrophoblast

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Uterine artery Uterine vein Ox - 90 Ox - 40 Ox – 20 Umbilical artery Umbilical vein Ox - 40 Placenta Trans placental pressure gradient in mm of Hg 35 7.5

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Prenatal circulation

Essential Factors for proper foetal circulation : 

Essential Factors for proper foetal circulation Functioning placenta Left umbilical vein Ductus venosus Valve of inferior vena cava directing blood properly to the foramen ovale Ductus arteriosus Pair of umbilical arteries

Shunts in foetal circulation : 

Shunts in foetal circulation At ductus venosus – directing blood straight to the IVC without losing oxygen for liver At foramen ovale – directing oxygenated blood to left atrium for distribution to the head, neck and brain At ductus arteriosus – to direct venous blood to the placenta by passing the lungs

Interesting facts of foetal circulation : 

Interesting facts of foetal circulation Ductus arteriosus carrying deoxygenated blood to the aorta, reaches it distal to the branches of the arch of aorta. This makes upper half of the body, brain and heart well oxygenated. The upper limb appears longer and well developed than the lower limb.

Sites where major admixtures of oxygenated and deoxygenated blood takes place in foetal circulation : 

Sites where major admixtures of oxygenated and deoxygenated blood takes place in foetal circulation Terminal part of IVC Both atria, particularly in right atrium Distal part of the arch of aorta Oxygen saturation in those situations are just enough to maintain nutrition of the foetal tissues.

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7th month (viable age) Pulmonary blood circulation increases Pressure within the left atrium increases Flow through the inter atrial septum gradually decreases The above changes makes way for the circulatory readjustments at birth

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Post-natal circulation

Circulatory changes occurring at birth : 

Circulatory changes occurring at birth Closure of the umbilical arteries Functional closure: few minutes after birth Actual obliteration: 2-3 months Cause of closure: change in oxygen tension Remnant: Distal part – Medial umbilical ligament Proximal part – Superior vesical artery

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Closure of the umbilical veins Shortly after closure of the arteries. Indicates entry of the blood for sometime after birth Remnant: Ligamentum teres hepatis So ligature of umbilical cord after waiting for few minutes provides additional 50cc of placental blood to the new born

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Closure of the ductus venosus Remnant: Ligamentum venosum at the posterior aspect of the liver

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Closure of the ductus arteriosus Functional closure: Immediately after birth Complete obliteration: 1-3 months Cause of closure: Release of Bradykinin from lung during initial inflation Remnant: Ligamentum arteriosum

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7th Week 3rd month

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Closure of foramen ovale Functional closure: Starts after birth Actual obliteration: About an year Cause of closure: Septum primum pressing against the septum secondum Remnant: Fossa Ovalis In 20% individuals perfect anatomical closure might never take place.

Defects in closure of Foramen ovale : 

Defects in closure of Foramen ovale Variety of Atrial septal defect. Asymptomatic at early part of life except murmur since there is only left to right shunt as the pressure in the left is always higher. When right atrial pressure increases then cyanotic spells can take place.

Probe patency of foramen ovale : 

Probe patency of foramen ovale Person asymptomatic Symptoms appear in case of decompensated heart diseases 20-25% human subjects As left atrial pressure is higher than the right atrial pressure flap like septum primum remains pressed on septum secondum The opening is so functionally closed though not anatomically closed

Patent Ductus Arteriosus : 

Patent Ductus Arteriosus The ductus arteriosus connects the pulmonary artery with the arch of the aorta during fetal life. PDA results when the ductus fails to close after birth.

Patent Ductus Arteriosus : 

Patent Ductus Arteriosus Increased pulmonary blood flow can result in pulmonary hypertension and reversal of the shunt, which is known as Eisenmenger’s Syndrome. This results in flow of desaturated blood to the lower extremities.

Patent Ductus Arteriosus : 

Patent Ductus Arteriosus Symptoms Children with small patent ductus are usually asymptomatic. Large left to right shunts develop symptoms of congestive heart failure such as tachypnea, tachycardia, poor feeding and slow growth Treatment Surgical division or ligation of the PDA

Patent ductus venosus : 

Patent ductus venosus Rare A variety of Porto systemic shunt. Can result in hepatic encephalopathy. Araki et al, 2003 presented such a case

References : 

References Gray’s Anatomy, 39th Edition. Shaw's textbook of Gynecology. Human Embryology- Dr A.K.Dutta. Text book of embryology – I.B.Singh. Congenital Heart Disease Conrad Cheung, 2006

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