Placenta
Umbilical cord
Normal

Author: Paul J. Kowalski, M.D. (see Authors page)

Revised: 26 September 2016, last major update September 2016

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed Search: Umbilical cord [title] placenta

Definition / General
  • The umbilical cord is the anatomic tubular structure that physically connects the developing intrauterine fetus to the placenta, which is anchored to the maternal uterine wall
Essential Features
  • Functions as the conduit by which oxygenated, nutrient rich blood from the mother (via the intervening placenta) reaches the fetus
  • Returns deoxygenated, nutrient poor blood from the fetus back to the mother
Terminology
  • The umbilicus (or navel) is the attachment site of the umbilical cord to the fetus
  • Two umbilical arteries in the umbilical cord return deoxygenated blood to the mother
  • One umbilical vein in the umbilical cord carries oxygenated blood to the fetus
  • Wharton's jelly is the mucopolysaccharide rich gelatinous substance that provides turgor regulation to the umbilical cord, and in which the two umbilical arteries and single umbilical vein are embedded
Clinical Features
  • Derived from the allantois and yolk sac during the fifth week of fetal development
  • A fetoplacental circulation (connection) develops when allantoic vessels establish continuity with the developing villi of the placenta
  • An allantoic duct remnant is seen in about 15% of umbilical cords
  • An omphalomesenteric duct remnant is seen in about 1.5% of umbilical cords
  • Two umbilical veins are initially present, but one atrophies during the second month of pregnancy
  • The two umbilical arteries, in the vast majority of deliveries (96%), anastomose with 1.5 cm of the placental insertion site
Gross Description
  • Average size: 55 - 60 cm length and 2.0 - 2.5 cm diameter in a term gestation
  • Pearly white on gross examination, bordering on semitranslucent on closer inspection (due to the gelatinous nature of Wharton's jelly)
  • Usually coiled in a counterclockwise direction, approximately 0.1 - 0.2 coils per centimeter of length
  • Insertion on the placenta is normally centrally located by mid gestation, but may become more eccentric as gestation proceeds
Gross Images

Images hosted on other servers:

Clamped umbilical cord still
attached to the fetal umbilicus

Micro Description
  • The two umbilical arteries have slightly thicker, double layered muscular walls without an elastic layer
  • The single umbilical vein has a thinner muscular wall containing a subintimal elastic layer
  • Intervening Wharton's jelly contains loose ground substance, a fine network of microfibrils and scattered nucleated cells (predominantly macrophages, myofibroblasts and mast cells)
  • The umbilical cord is surfaced by a single layer of amnion, which is continuous with the surface of the placenta and the fetal skin
Micro Images

Images hosted on other servers:

A normal three vessel umbilical cord