Umbilical Cord

DEFINITION:

• The umbilical cord or funis forms the connecting link between the fetus and the placenta through which the fetal blood flows to and from the placenta. 
• It extends from the fetal umbilicus to the fetal surface of the placenta.
• The umbilical cord stump of a newborn most frequently sloughs off about the 10th day after delivery

DEVELOPMENT:

• Developed from the connective stalk or body stalk

STRUCTURES:

• Covering epithelium:Single layer of amniotic epithelium showing  stratification 
• Wharton’s jelly:(The extracellular matrix )Protective function to the umbilical vessels.

Blood vessels:

• Two arteries and two veins
• Umbilical vesicle attains full development in 4 week

Arteries:

• Origin:Internal iliac arteries of the fetus
• Function: Carry venous blood from the fetus to the placenta.
• The two arteries are smaller in diameter than the veins
• Derivatives:Distal parts(Urachus) form medial umbilical ligaments & proximal portions remain open as superior vesical arteries
• When fixed in their normally distended state, the umbilical arteries exhibit transverse intimal folds of Hoboken across their lumen
• Presence of  single umbilical artery is often associated with fetal congenitalabnormalities

Veins:

• Right one disappears by the 4th month, leaving behind one vein which carries oxygenated blood from the placenta to the fetus.
• Function:Carry oxygenated blood towards the fetus

Derivatives:

• Ligamentum teres(from left umbilical vein)
• Ligamentum venousm(from ductus venosus )

Drainage:

• Sinus venosus(Initially) 
• Hepatic sinusoids(by 5th week)
• Hepatocardiac channel through the ductus venosus(after right vein disappears)
• Remnant of the umbilical vesicle (yolk sac) and its vitelline duct:Meckel’s diverticulum(proximal part)
• Allantois
• Obliterated extraembryonic coelom

CHARACTERISTICS:

• Length:40 cm(variation of 30–100 cm)
  • At birth, the mature cord is approximately 50–60 cm in length and 12 mm in diameter. 
  • A long cord is defined as more than 100 cm, and a short cord as less than 30 cm.
• Diameter:1.5 cm(variation of 1–2.5 cm)
• Thickness:Non uniform with false knots(Folding and tortuosity of the vessels within the cord itself creates false knots which are essentially varices).
• The exterior of umbilical cord is dull white, moist and covered by amnion through which the three umbilical vessels may be seen.
• Spiral twist from the left to right.
  • Umbilical coiling index (UCI) :The number of complete coils divided by the length of the cord in centimeters. 
  • Clinically, hypocoiling (UCI 0.3 coils/cm) is related to fetal-growth restriction and intrapartum fetal acidosis and asphyxia. 
  • Both have been linked to trisomies and single umbilical artery
• Umbilical arteries Have got well-developed muscular coat:Effective closure of the arteries soon after birth of the baby

ATTACHMENT:

Fetal attachment:

• Early period:ventral surface of the embryo close to caudal extremity
• On closure of coelom:center of the abdomen( 4th month)

Placental attachment:

• Eccentric insertion:Between the center and the edge of the placenta
• Central
• Marginal
• Velamentous insertion:On chorion laeve

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