U01.07.005 Fetal-postnatal derivatives

Here’s a table summarizing the fetal structures and their postnatal derivatives for USMLE Step 1:

Fetal Structure	Postnatal Derivative	Notes
Ductus Arteriosus	Ligamentum Arteriosum	Near the left recurrent laryngeal nerve.
Ductus Venosus	Ligamentum Venosum	Remnant of the fetal shunt from the umbilical vein to the IVC.
Foramen Ovale	Fossa Ovalis	Closure after birth due to increased left atrial pressure.
Allantois	Urachus → Median Umbilical Ligament	Urachus connects bladder to umbilicus, becomes median umbilical ligament.
Umbilical Arteries	Medial Umbilical Ligaments	Carry deoxygenated blood; become medial umbilical ligaments after birth.
Umbilical Vein	Ligamentum Teres Hepatis (Round Ligament)	Contained in falciform ligament.
Notochord	Nucleus Pulposus	Remnant in intervertebral discs.

The ductus arteriosus becomes the ligamentum arteriosum near the left recurrent laryngeal nerve.
The ductus venosus becomes the ligamentum venosum.
The foramen ovale becomes the fossa ovalis after birth.
The allantois becomes the urachus, which turns into the median umbilical ligament.
The umbilical arteries become the medial umbilical ligaments.
The umbilical vein becomes the ligamentum teres hepatis.
The notochord contributes to the nucleus pulposus of intervertebral discs.

These derivatives are important in understanding congenital anomalies, developmental defects, and anatomical variations.

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