- Fetal Circulation
- Contain one vein and 2 arteries.
- Made up of Wharton’s jelly
- Normal length=50cm
- Arteries carry Deoxygenated blood and waste products from the fetus.
- Vein carries Oxygenated blood and provide oxygen and nutrients to the fetus.
- Pressure in Umbilical vein>10mm Hg
- Pressure in Umbilical artery.>60mm Hg
- Right umbilical vein is disappearing by the 4 months.
The Fetal Circulation
There are several temporary structures inaddition to the
placenta itself and the umblical cord and these enable the
fetal circulation to take place while allowing for the changes at
- The Umbilical vein Leads from the umblical cord to the underside of the liver and carries blood rich in oxygen and nutrients. It has a branch which joins the portal vein and supplies the liver.
- The ductus vensous (from a vein to a vein) connects the umblica vein to the inferior venacava. At this point the blood mixes with deoxygenated blood returning from the lower parts of the body. Thus the blood throughout the body is at best partially oxygenated.
- The foramen ovale (oval opening) is a temporary opening between the atria which allows the majority of blood entering from the inferior vencava to pass across into the left atrium. The reason for this diversion is that the blood does not need to pass through the lungs since it is already oxygenated.
- The ductus arteriosus (from an artery to an artery) leads from the bifuraction of the pulmonary artery to the descending aorta, entering it just beyond the point where the subclavian and carotid arteries leave. The hypogastric arteries branch off from the internal iliac arteries and become umbilical arteries when they enter the umblical cord. They return blood to the placenta. This is the only vessel inthe fetus which carries unmixed blood.
Changes in Circulation after Birth-
- Closure of ductus venosum and becomes ligamentum Venosum. Umbilical Vein becomes ligamentum teres by one year time.
- Closure of ductus arteriosus occurs after establishment of Pulmonary Ventilation. Ductus arteriosus becomes ligamentum arteriosum
- Closure of foramen ovale occurs due to rise in pressure in left atrium and close foramen ovale gives fossa ovalis.
- Obliterated umbilical arteries form lateral umbilical ligaments. Functional closure occurs soon after birth but anatomical closure occurs in about one year time
- The umbilical vein → the ligamentaum teres
- The ductus venosus → the ligamentum venosum
- The ductus arteriosus → the ligamentum arteriousm
- The foramen ovale → the Fossa ovalis
- The hypogastric arteries → the obliterated hypogastic arteries
Umbilical Cord (Funis)-
Umbilical cord of Funis is a long cord like structure that connects the foetal umbilicus with foetal surface of placenta. It is developed from body stalk of mesodormal cells stretching between embryonic disc and chorion.
- It is the life line between placenta and foetus supplying oxygen and nutrients for foetus and disposing waste products.
- Exchange of fluid and electrolyte between umbilical vessels and amniotic fluid.
Battle dore Placenta-
- This cord is attached to the margin of placenta.
- Increase chances of cord compression.
The cord is attached to the membrane.
1. No cord (achordia)
- Increase chances of cord prolapsed.
- Cord entanglement round the neck or the body.
- True knot is rare, even with true knot the fetal vesse are protected from compression by Wharton’s Jelly.
- False knot are the result of accumulation of Wharton’s Jelly.
4.Single Umbilical Artery-
- Failure of development of one artery or Atrophy.
- More common is twin, baby born with Diabetic mother or is Polyhydramnios.
- Frequently associated with congenital malformation of the fetus, trisomy of 18(Edwards Syndrome)