Umbilical cord begins development around __-__ weeks.

Umbilical cord begins development around __-__ weeks.

• A. 7-8
• B. 4-5
• C. 9-10
• D. 11-12

Answer: (A)

The umbilical cord starts to take shape as the extraembryonic membranes organize and the vascular connections between embryo and placenta form, a process that is underway around 7 to 8 weeks. By this time, the primitive stalk has evolved into a recognizable cord with the developing vessels enclosed by Wharton’s jelly. Earlier weeks (around 4–6) involve initial formation of the stalk and vessels, but the cord isn’t yet a distinct, identifiable structure. Later weeks (9–12) feature more mature placental and cord development, but the beginning of the cord’s formation is best placed at 7–8 weeks.

The umbilical cord starts to take shape as the extraembryonic membranes organize and the vascular connections between embryo and placenta form, a process that is underway around 7 to 8 weeks. By this time, the primitive stalk has evolved into a recognizable cord with the developing vessels enclosed by Wharton’s jelly. Earlier weeks (around 4–6) involve initial formation of the stalk and vessels, but the cord isn’t yet a distinct, identifiable structure. Later weeks (9–12) feature more mature placental and cord development, but the beginning of the cord’s formation is best placed at 7–8 weeks.