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10. During anatomy lab, a medical student notes a fibrous band that runs on the visceral surface of the liver. It is attached on one end to the inferior vena cava and on the other end to the left branch of the portal vein. In the embryo, this structure corresponds to the A. Ductus venosus B. Ligamentum teres C. Ligamentum venosum D. Umbilical arteries E. Umbilical vein
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Dr_Osler
| Forum Newbie  Topics: 3 Posts: 55
Answer is C The ligamentum venosum (option C) is the fibrous remnant of the ductus venosus of the fetal circulation. Usually, it is attached to the left branch of the portal vein within the porta hepatis. The ductus venosus (option A) shunts a significant majority (80%) of the blood flow of the umbilical vein directly to the inferior vena cava. Thus, it allows oxygenated blood from the placenta to bypass the liver. In conjunction with the other fetal shunts, the foramen ovale and ductus arteriosus, it plays a critical role in preferentially shunting oxygenated blood to the fetal brain. The ductus venosus is open at the time of the birth and is the reason why umbilical vein catheterization works. Ductus venosus naturally closes during the first week of life in most full-term neonates; however, it may take much longer to close in pre-term neonates. The ligamentum teres (option B) is a degenerative string of tissue that exists in the free edge of the falciform ligament of the liver. Anatomically, it divides the left part of the liver into medial and lateral segments. The ligamentum teres represents the remnant of the fetal left umbilical vein. Prenatally and for a month or two after birth, the left umbilical vein is patent, subsequently degenerating to fibrous tissue, the ligamentum teres. The umbilical vein inserts around the umbilicus and is an important landmark of the inner surface of the anterior abdominal wall. Best wishes  Attached Files: Fetal Circulation.jpg (52 KB, 36 downloads) Edited by Dr_Osler on Mar 30, 2010 - 3:47 AM
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Dr_Osler
| Forum Newbie Topics: 3 Posts: 55
Fetal postnatal derviatives:- 1. Umbilical vein —ligamentum teres hepatis 2. UmbiLical arteries-mediaL umbilical ligaments 3. Ductus arteriosus—ligamentum arteriosum 4. Ductus venosus—ligamentum venosum Edited by Dr_Osler on Mar 30, 2010 - 3:39 AM
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The correct answer is A. This question could have tricked you if you didn't catch the key words, "in the embryo." If you read the question too quickly and thought you were going to be asked to identify the structure described, you probably chose choice C (ligamentum venosum), since that is indeed the structure in question. However, in the embryo, this fibrous band is actually the ductus venosus. The ductus venosus is an embryonic vessel that allows blood to bypass the fetal liver; this prevents the depletion of oxygen and nutrient-rich blood in the hepatic sinusoids. The embryonic umbilical vein (choice E) actually becomes the fibrous ligamentum teres (choice B). The ligamentum teres is located in the free margin of the falciform ligament. The embryonic umbilical arteries (choice D) become the medial umbilical ligaments.
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Dr_Osler
| Forum Newbie Topics: 3 Posts: 55
thanks a lot for the correction, really it is a nice tricky questions, theat by a one word change the whole answer. Awesome sharing
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 Similar forum topicsCVS Embryology Q1 CVS Embryology Q2 CVS Embryology Q3 | Related resources High-Yield Embryology Embryology - Board Review Series (BRS) Elsevier's Integrated Anatomy and Embryology |
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