--- title: "Umbilical Arteries | Anatomy and Physiology I" description: "Umbilical arteries carry deoxygenated fetal blood to the placenta, linking fetal circulation with gas exchange and waste removal in Anatomy and Physiology I." canonical: "https://fiveable.me/anatomy-physiology/key-terms/umbilical-arteries" type: "key-term" subject: "Anatomy and Physiology I" unit: "Unit 20" --- # Umbilical Arteries | Anatomy and Physiology I ## Definition Umbilical arteries are the two fetal vessels that carry oxygen-poor, waste-filled blood from the fetus to the placenta. In Anatomy and Physiology I, they are a core part of fetal circulation. ## What It Is Umbilical arteries are the two blood vessels in fetal circulation that carry blood away from the fetus and toward the placenta. Their job is not to feed the fetus with oxygen, but to send blood that is low in oxygen and high in waste products to the placenta, where exchange with the mother can happen. A common point of confusion is that arteries do not always carry oxygen-rich blood. In adult circulation, arteries usually carry oxygenated blood away from the heart, so that pattern is easy to memorize first. In the fetus, though, the label is based on direction of flow, not oxygen level. Umbilical arteries still count as arteries because they carry blood away from the fetus toward the placenta. These vessels are part of a special circulation route that exists before birth. The fetus does not use its lungs for gas exchange yet, so oxygen and carbon dioxide are handled through the placenta. The umbilical arteries carry blood from the fetal internal iliac region through the umbilical cord to the placenta, where the fetal and maternal blood supplies stay separate but exchange gases, nutrients, and wastes across a thin barrier. The blood in the umbilical arteries contains carbon dioxide and metabolic waste that the fetus cannot clear on its own. Once that blood reaches the placenta, the maternal side can remove wastes and bring in oxygen and nutrients. That makes the placenta a temporary support organ and the umbilical arteries a transport route that keeps fetal tissues supplied indirectly. After birth, this pathway is no longer needed. The fetal circulation shifts as the lungs take over for gas exchange, and the umbilical vessels are no longer part of circulation. In Anatomy and Physiology I, this topic usually comes up when you trace fetal blood flow, compare fetal and adult circulation, or identify how the placenta fits into homeostasis before birth. ## Why It Matters Umbilical arteries matter because they show how fetal circulation solves a problem the newborn body does not have to solve later: getting oxygen and removing wastes without using the lungs. If you can trace these vessels, you can trace the whole fetal circulation pattern, which is a common skill in anatomy and physiology. They also make the word artery make sense in a more precise way. This term helps you separate flow direction from oxygen content, which is a big idea in cardiovascular anatomy. That distinction comes up again with other fetal structures, where the names and the contents do not always match the adult pattern you already know. In class, this term often sits next to the placenta, umbilical vein, ductus venosus, and ductus arteriosus. Together, those structures explain how fetal blood bypasses or reroutes parts of the adult circulation. If one vessel is missing from your mental map, the whole route gets fuzzy. It also connects to the cardiovascular transition at birth. Once breathing starts, the old exchange system is no longer needed, so fetal vessels and shunts close or change function. Knowing what the umbilical arteries do before birth makes it easier to understand why those changes matter immediately after delivery. ## Connections ### Placenta The placenta is the exchange organ the umbilical arteries send blood to. It is where fetal waste gets removed and oxygen and nutrients are taken up from the maternal side. If you are tracing fetal circulation, the placenta is the destination for blood leaving through the umbilical arteries and the source of what comes back through the umbilical vein. ### [Umbilical Vein](/anatomy-physiology/key-terms/umbilical-vein) The umbilical vein does the opposite job of the umbilical arteries. It carries oxygenated, nutrient-rich blood from the placenta back to the fetus. Together, the vein and arteries form the core in-and-out route through the umbilical cord, and comparing them is a fast way to check whether you understand fetal circulation correctly. ### Fetal Circulation Umbilical arteries are one piece of the larger fetal circulation pattern. Fetal circulation includes special routes that let blood bypass the lungs and partly bypass the liver before birth. When you study this system, the umbilical arteries help you see how blood enters the placenta, gets exchanged, and returns through a separate vessel. ### [Cardiovascular Transition at Birth](/anatomy-physiology/key-terms/cardiovascular-transition-birth) At birth, the circulation pattern changes because the lungs begin gas exchange. The umbilical arteries are no longer needed once placental exchange stops. This connection helps explain why fetal vessels and shunts close after delivery and why the newborn circulatory system starts functioning like the adult system. ## On the AP Exam A quiz or lab question may show a fetal circulation diagram and ask you to label which vessel carries blood from the fetus to the placenta. That is the umbilical arteries. You may also be asked to explain why they are arteries even though they carry deoxygenated blood, so focus on direction of flow, not oxygen content. On image-based questions, look for the vessels inside the umbilical cord heading away from the fetus. In written responses, use them to trace the route of waste removal before birth and connect that route to the placenta and umbilical vein. If your instructor gives a birth transition scenario, mention that these vessels are no longer functional once the newborn begins breathing and placental exchange ends. ## umbilical arteries vs Umbilical Vein These two vessels are easy to mix up because both run through the umbilical cord. The umbilical arteries carry blood from the fetus to the placenta, while the umbilical vein carries blood from the placenta back to the fetus. The direction is the fastest way to tell them apart. ## Key Takeaways - Umbilical arteries carry deoxygenated, waste-rich blood from the fetus to the placenta. - They are called arteries because they carry blood away from the fetus, not because the blood is oxygen-rich. - They are part of fetal circulation, which works differently from adult circulation because the lungs are not yet doing gas exchange. - The placenta receives this blood, exchanges wastes and gases, and returns oxygenated blood through the umbilical vein. - After birth, the umbilical arteries are no longer part of the active circulation pathway. ## FAQs ### What are umbilical arteries in Anatomy and Physiology I? Umbilical arteries are the two vessels that carry deoxygenated blood from the fetus to the placenta during pregnancy. They are part of fetal circulation, not adult circulation. Their main job is to move waste-filled blood away from the fetus so exchange can happen across the placenta. ### Do umbilical arteries carry oxygenated blood? No. Umbilical arteries carry oxygen-poor blood, which is a common exception to the usual adult pattern. They are still arteries because they carry blood away from the fetus. The oxygenated blood comes back to the fetus through the umbilical vein. ### How are umbilical arteries different from the umbilical vein? The umbilical arteries move blood from the fetus to the placenta, while the umbilical vein moves blood from the placenta to the fetus. That makes them opposite directions in the same cord. If you can remember the direction of flow, you can usually identify them on a diagram or test question. ### Why do umbilical arteries matter before birth? Before birth, the fetus is not using its lungs for gas exchange, so the placenta does that job instead. Umbilical arteries make that exchange possible by bringing waste-rich blood to the placenta. Without them, fetal tissues would not have a route for removing carbon dioxide and other wastes. ## Related Study Guides - [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-arteries#resource","name":"Umbilical Arteries | Anatomy and Physiology I","url":"https://fiveable.me/anatomy-physiology/key-terms/umbilical-arteries","learningResourceType":"Concept explainer","educationalLevel":"AP® / High School","about":{"@id":"https://fiveable.me/anatomy-physiology/key-terms/umbilical-arteries#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"},"author":{"@type":"Organization","@id":"https://fiveable.me/editorial#content-team","name":"Fiveable Content Team","url":"https://fiveable.me/editorial","parentOrganization":{"@id":"https://fiveable.me/#organization"},"member":[{"@type":"Person","name":"Amanda DoAmaral","sameAs":["https://www.linkedin.com/in/adoamaral"]},{"@type":"Person","name":"Becky Bahr","sameAs":["https://www.linkedin.com/in/becky-bahr-b52743132"]}]},"publisher":{"@type":"Organization","name":"Fiveable","url":"https://fiveable.me"}},{"@type":"DefinedTerm","@id":"https://fiveable.me/anatomy-physiology/key-terms/umbilical-arteries#term","name":"umbilical arteries","description":"Umbilical arteries are the two fetal vessels that carry oxygen-poor, waste-filled blood from the fetus to the placenta. 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