Yolk sac roles vs Allantois roles
How to tell Yolk sac roles and Allantois roles apart when a board question makes them look alike.
Yolk sac is early blood/germ cells/vitelline duct; allantois is urachus and bladder-related remnant.
Side by side
Yolk sac provides early hematopoiesis, primordial germ cell origin, and vitelline duct connection; persistent vitelline duct can form Meckel diverticulum.
Allantois contributes to early blood vessel/urinary development and the urachus; persistent urachus can cause patent urachus, urachal cyst, sinus, or diverticulum.
Yolk sac contributes early hematopoiesis, primordial germ cell origin, and midgut connection through vitelline duct.
Allantois contributes to urachus/median umbilical ligament and early bladder/umbilical vessel development associations.
Vitelline duct remnant = Meckel diverticulum with ectopic gastric mucosa.
Allantois/urachus remnant = urine drainage from umbilicus, midline urachal cyst, sinus, or diverticulum.
The repair move
Before naming the answer, force the stem through the separator: Yolk sac is early blood/germ cells/vitelline duct; allantois is urachus and bladder-related remnant.
Try a free question
CoreA medical student is studying embryologic structures. One extraembryonic membrane provides early hematopoiesis (3rd-8th week), serves as the origin of primordial germ cells, and connects to the embryonic gut via the vitelline (omphalomesenteric) duct. Which structure is this?
Show answer and explanation
Answer: A. Yolk sac. The yolk sac provides early embryonic hematopoiesis (3rd-8th week, then transferred to liver, spleen, then bone marrow), is the origin of primordial germ cells (which migrate to the gonadal ridges), and connects to the midgut via the vitelline duct. Persistence of the vitelline duct produces Meckel diverticulum.
Why the other choices are tempting
- B. Allantois contributes to early urinary development and forms the urachus (median umbilical ligament).
- C. Amnion is the inner extraembryonic membrane forming the amniotic sac with amniotic fluid.
- D. Chorion forms the outer placental membrane.
- E. Decidua is maternal endometrium responding to pregnancy.
Flashcards
Tap a card to flip it.
What clue supports Yolk sac roles?
Choose Yolk sac roles when the stem gives this pattern: Yolk sac contributes early hematopoiesis, primordial germ cell origin, and midgut connection through vitelline duct.
What clue supports Allantois roles?
Choose Allantois roles when the stem gives this contrasting pattern: Allantois contributes to urachus/median umbilical ligament and early bladder/umbilical vessel development associations.
Quick answers
What is the fastest way to tell Yolk sac roles from Allantois roles?
Yolk sac is early blood/germ cells/vitelline duct; allantois is urachus and bladder-related remnant.
What is the key clue for Yolk sac roles?
Yolk sac provides early hematopoiesis, primordial germ cell origin, and vitelline duct connection; persistent vitelline duct can form Meckel diverticulum.
What is the key clue for Allantois roles?
Allantois contributes to early blood vessel/urinary development and the urachus; persistent urachus can cause patent urachus, urachal cyst, sinus, or diverticulum.