--- title: "Umbilical Vein | Anatomy and Physiology I" description: "Umbilical vein: the fetal vessel that carries oxygen-rich blood from the placenta to the fetus and later becomes the ligamentum teres in Anatomy and Physiology I." canonical: "https://fiveable.me/anatomy-physiology/key-terms/umbilical-vein" type: "key-term" subject: "Anatomy and Physiology I" unit: "Unit 28" --- # Umbilical Vein | Anatomy and Physiology I ## Definition The umbilical vein is the fetal blood vessel that carries oxygen-rich, nutrient-filled blood from the placenta to the fetus. In Anatomy and Physiology I, it is part of fetal circulation and later closes after birth. ## What It Is The umbilical vein is the vessel in the umbilical cord that brings oxygen-rich blood from the placenta to the fetus during pregnancy. In Anatomy and Physiology I, you study it as part of fetal circulation, the special blood flow pattern that keeps a fetus supplied before birth. It is one of the three vessels in the umbilical cord. The two umbilical arteries carry blood the other way, taking deoxygenated blood and wastes from the fetus back to the placenta. That direction matters, because the placenta is the site where fetal blood picks up oxygen and nutrients from the mother’s blood supply without the two blood supplies directly mixing. After entering the fetus, the umbilical vein heads toward the liver. A large portion of this blood flows through the liver, and some of it is diverted through a fetal shunt called the ductus venosus so oxygenated blood can reach the heart and brain more quickly. That routing is a good example of how fetal circulation is built for efficiency, not for the postnatal pattern you see after birth. The blood in the umbilical vein is not just oxygen-rich. It also carries glucose, amino acids, and other materials the fetus needs for growth. That makes the vessel part of a larger supply chain: placenta, umbilical cord, fetal liver, and then the rest of the fetal circulation. After birth, the umbilical vein is no longer needed because the newborn starts using the lungs for oxygen exchange. The vessel closes and becomes the ligamentum teres hepatis, a fibrous remnant in the liver region. So when you see the term, think of both its prenatal job and its postnatal leftover structure. ## Why It Matters The umbilical vein shows how the fetal body solves a problem that adult anatomy does not have: how to get oxygen and nutrients from the placenta to organs that are still developing. That makes it a clean example of structure matching function in Anatomy and Physiology I. It also helps you understand fetal circulation as a system, not as isolated vessels. The umbilical vein works with the placenta, umbilical arteries, and fetal shunts to direct blood where it is needed most. If you can trace blood flow through this vessel, you can usually trace the rest of fetal circulation too. This term often comes up when your instructor wants you to compare fetal and adult circulation or explain what changes after birth. You may also see it in diagrams, labeling activities, or questions that ask you to identify which vessel carries oxygenated blood in the umbilical cord. Knowing the umbilical vein keeps you from flipping the direction of flow, which is a common mistake. ## Connections ### Placenta The placenta is the exchange organ that makes the umbilical vein useful. Oxygen, nutrients, and other materials move across the placenta before blood enters the umbilical vein and heads to the fetus. If the placenta is not functioning well, the blood in the umbilical vein cannot deliver what the developing fetus needs. ### [Umbilical Cord](/anatomy-physiology/key-terms/umbilical-cord) The umbilical vein runs inside the umbilical cord, where it is paired with two umbilical arteries. A cord diagram usually shows one vein and two arteries, so this term helps you read fetal anatomy images correctly. The cord is the physical connection between fetus and placenta, and the vein is the main return route for oxygenated blood. ### Fetal Circulation The umbilical vein is one piece of fetal circulation, the temporary blood flow pattern used before birth. It feeds oxygen-rich blood into a route that includes the liver and fetal shunts, then eventually reaches the heart and body. Understanding the vein makes the rest of the fetal circuit easier to follow. ### [Foramen Ovale](/anatomy-physiology/key-terms/foramen-ovale) The foramen ovale is another fetal shunt that works alongside the umbilical vein’s blood supply. The vein brings oxygenated blood in, and the foramen ovale helps send some of that blood from the right atrium to the left atrium so it can reach the brain and body quickly. Together, they show how fetal circulation bypasses the lungs. ## On the AP Exam A diagram question may ask you to label the umbilical vein or pick the vessel carrying oxygen-rich blood from the placenta to the fetus. A short-answer prompt might ask you to trace fetal blood flow in order, starting with the placenta and ending at the fetal heart. In that kind of item, you need to state the direction of flow, not just the name of the vessel. You can also see it in comparison questions about fetal versus adult circulation. The newborn no longer uses the umbilical vein for exchange, so a later question may ask what it becomes after birth. If you are looking at a case study or lab image, identify whether the vessel is part of the umbilical cord and whether it carries oxygenated or deoxygenated blood before you answer. ## Key Takeaways - The umbilical vein carries oxygen-rich blood from the placenta to the fetus. - It is one of three vessels in the umbilical cord, alongside two umbilical arteries. - In fetal circulation, the blood it carries can pass through the liver and then into the rest of the fetal body. - After birth, the umbilical vein closes and becomes the ligamentum teres hepatis. - If you remember one thing, remember the direction: placenta to fetus, not fetus to placenta. ## FAQs ### What is the umbilical vein in Anatomy and Physiology I? The umbilical vein is the fetal blood vessel that carries oxygenated, nutrient-rich blood from the placenta to the fetus. It is part of the umbilical cord and fetal circulation. In class diagrams, it is the vessel with flow toward the fetus, not back to the placenta. ### Does the umbilical vein carry oxygenated or deoxygenated blood? It carries oxygenated blood in fetal circulation. That can feel backward if you are used to adult veins and arteries, since fetal vessels are named by where blood flows, not by oxygen level. The umbilical arteries do the opposite and carry deoxygenated blood back to the placenta. ### What happens to the umbilical vein after birth? After birth, the umbilical vein is no longer needed because the baby’s lungs take over oxygen exchange. The vessel closes and becomes the ligamentum teres hepatis, a fibrous remnant near the liver. This is a common detail in fetal development questions. ### How is the umbilical vein different from the umbilical arteries? The umbilical vein brings oxygen-rich blood from the placenta to the fetus, while the two umbilical arteries carry blood and wastes from the fetus back to the placenta. So even though the names sound similar, they move blood in opposite directions. That difference shows up often in fetal circulation diagrams. ## Related Study Guides - [28.3 Fetal Development ](/anatomy-physiology/unit-28/3-fetal-development/study-guide/9VWtVO6TlVol3Zg7) - [20.6 Development of Blood Vessels and Fetal Circulation ](/anatomy-physiology/unit-20/6-development-blood-vessels-fetal-circulation/study-guide/P7hzmuTAzmqbuO6c) ## About This Document Canonical Fiveable pages are available as Markdown at the same path plus `.md`. - [llms.txt](https://fiveable.me/llms.txt): index of Fiveable's sections and URL patterns - [llms-full.txt](https://fiveable.me/llms-full.txt): complete subject and unit listing - [MCP server](https://fiveable.me/mcp): call Fiveable as tools instead of fetching pages (`https://fiveable.me/api/mcp`) - [MCP server for AP teachers](https://fiveable.me/mcp/teachers): a teacher's classes, assignments and AP-rubric grading (`https://fiveable.me/api/mcp/teacher`) ## Structured Data ```json {"@context":"https://schema.org","@graph":[{"@type":"LearningResource","@id":"https://fiveable.me/anatomy-physiology/key-terms/umbilical-vein#resource","name":"Umbilical Vein | Anatomy and Physiology I","url":"https://fiveable.me/anatomy-physiology/key-terms/umbilical-vein","learningResourceType":"Concept explainer","educationalLevel":"AP® / High School","about":{"@id":"https://fiveable.me/anatomy-physiology/key-terms/umbilical-vein#term"},"audience":{"@type":"EducationalAudience","educationalRole":"student"},"dateModified":"2026-07-03T02:20:43.193Z","isPartOf":{"@type":"Collection","name":"Anatomy and Physiology I Key Terms","url":"https://fiveable.me/anatomy-physiology/key-terms"},"publisher":{"@type":"Organization","name":"Fiveable","url":"https://fiveable.me"}},{"@type":"DefinedTerm","@id":"https://fiveable.me/anatomy-physiology/key-terms/umbilical-vein#term","name":"umbilical vein","description":"The umbilical vein is the fetal blood vessel that carries oxygen-rich, nutrient-filled blood from the placenta to the fetus. 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