--- title: "Umbilical Cord | Anatomy and Physiology I" description: "Umbilical cord is the fetal lifeline to the placenta, carrying oxygen and nutrients in and waste out, and it changes fast at birth in Anatomy and Physiology I." canonical: "https://fiveable.me/anatomy-physiology/key-terms/umbilical-cord" type: "key-term" subject: "Anatomy and Physiology I" unit: "Unit 28" --- # Umbilical Cord | Anatomy and Physiology I ## Definition The umbilical cord is the tube-like structure that connects the fetus to the placenta and carries blood through the umbilical vessels. In Anatomy and Physiology I, it explains how the fetus gets oxygen, nutrients, and waste removal before birth. ## What It Is The umbilical cord is the fetus's connection to the placenta during pregnancy. It carries blood between the two so the fetus can receive oxygen and nutrients and get rid of carbon dioxide and other wastes before the lungs and digestive system are fully working. In Anatomy and Physiology I, the cord is usually described as having two umbilical arteries and one umbilical vein. That arrangement can feel backward at first if you are thinking about adult circulation. The umbilical vein carries oxygen-rich blood from the placenta to the fetus, while the umbilical arteries carry blood away from the fetus and back to the placenta. The naming follows where the vessel is going, not whether the blood is oxygen-rich or oxygen-poor. The cord is protected by Wharton's jelly, a slippery, gelatinous connective tissue that cushions the vessels. That protection matters because the cord is flexible and can twist, bend, and get compressed as the fetus moves. If those vessels were not protected, blood flow could be interrupted more easily. A typical cord is about 50 cm long, which gives the fetus enough room to move without pulling the placenta too tightly. It also serves as a visible link to the placenta's job as the exchange organ. The fetus does not directly mix blood with the mother, instead the placenta handles the exchange while the umbilical cord acts as the transport route. At birth, the cord is clamped and cut, which ends placental circulation. Once the newborn takes over breathing and feeding, the cord is no longer needed. The small stump left on the abdomen dries out and falls off in the first few weeks after birth. ## Why It Matters The umbilical cord shows how fetal circulation works before birth, which is a big idea in Anatomy and Physiology I. It ties together the placenta, blood vessels, and the fetus's changing needs during pregnancy. If you understand the cord, a lot of prenatal circulation makes more sense, especially why the fetus uses the placenta instead of the lungs for gas exchange. It also connects directly to the newborn transition at birth. When the cord is clamped, the infant loses the placental route for oxygen and nutrients, so the body has to shift fast to breathing air and circulating blood through the lungs. That handoff connects to other birth-related concepts like the first breath, changing blood flow patterns, and postnatal adaptation. You will also see the umbilical cord when you study fetal anatomy, placental function, and the difference between fetal and adult circulation. It is one of those structures that looks simple but explains a whole system: transport, protection, and developmental change all in one place. ## Connections ### Placenta The placenta is the exchange organ the umbilical cord connects to. The cord does not do the exchanging by itself, it just carries blood to and from the placenta, where oxygen, nutrients, and wastes move across the barrier between mother and fetus. ### [Umbilical Arteries](/anatomy-physiology/key-terms/umbilical-arteries) The two umbilical arteries carry blood from the fetus to the placenta. This is a common place to mix up fetal circulation, because in adult circulation arteries usually carry oxygen-rich blood. Here, the artery label refers to direction away from the heart, not oxygen content. ### [Umbilical Vein](/anatomy-physiology/key-terms/umbilical-vein) The umbilical vein brings oxygenated, nutrient-rich blood from the placenta back to the fetus. It is the main vessel students track when they follow how the fetus receives what it needs before birth. ### [Apgar Score](/anatomy-physiology/key-terms/apgar-score) The Apgar score is used right after birth to assess how well the newborn is adapting. The umbilical cord has just been cut, so the baby is now relying on breathing and circulation changes, which makes the Apgar timing especially relevant. ## On the AP Exam A quiz question might ask you to label the umbilical cord on a fetal circulation diagram or identify which vessel carries oxygenated blood to the fetus. You may also be asked to trace what happens when the cord is clamped at birth and explain why the newborn must switch from placental exchange to lung-based respiration. On diagrams, watch for the two umbilical arteries and one umbilical vein, since that vessel pattern is easy to test. In short-answer questions, use the cord to connect the placenta to fetal transport, not to adult-style circulation. If a lab image or model shows the cord attached to the placenta, you should be able to explain its protective role, its vessels, and what changes after delivery. ## umbilical cord vs Placenta The placenta and umbilical cord work together, but they are not the same structure. The placenta is the exchange surface where nutrients, gases, and wastes move across, while the umbilical cord is the physical connection that transports blood between the fetus and that exchange surface. ## Key Takeaways - The umbilical cord connects the fetus to the placenta and serves as the transport link for fetal blood during pregnancy. - It usually contains two umbilical arteries and one umbilical vein, all protected by Wharton's jelly. - The cord carries oxygen and nutrients to the fetus and removes wastes, but the actual exchange happens in the placenta. - At birth, clamping and cutting the cord ends placental circulation and forces the newborn to switch to breathing air. - If you are tracing fetal circulation, the cord is the pathway that explains how the fetus survives before the lungs take over. ## FAQs ### What is the umbilical cord in Anatomy and Physiology I? The umbilical cord is the fetal structure that connects the fetus to the placenta during pregnancy. It carries blood through the umbilical vessels so the fetus can get oxygen and nutrients and remove wastes before birth. ### What is inside the umbilical cord? The umbilical cord usually contains two umbilical arteries and one umbilical vein. These vessels are surrounded by Wharton's jelly, which cushions them and helps keep blood flow from getting pinched off. ### How is the umbilical cord different from the placenta? The placenta is the exchange organ, and the umbilical cord is the connection to it. Blood actually exchanges gases and nutrients in the placenta, while the cord just transports blood back and forth between fetus and placenta. ### What happens to the umbilical cord after birth? After delivery, the cord is clamped and cut, which stops the fetal connection to the placenta. The small stump left on the newborn's abdomen dries up and falls off in the first few weeks after birth. ## Related Study Guides - [28.2 Embryonic Development ](/anatomy-physiology/unit-28/2-embryonic-development/study-guide/0JqK7PQo4SvTlspv) ## 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-cord#resource","name":"Umbilical Cord | Anatomy and Physiology I","url":"https://fiveable.me/anatomy-physiology/key-terms/umbilical-cord","learningResourceType":"Concept explainer","educationalLevel":"AP® / High School","about":{"@id":"https://fiveable.me/anatomy-physiology/key-terms/umbilical-cord#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-cord#term","name":"umbilical cord","description":"The umbilical cord is the tube-like structure that connects the fetus to the placenta and carries blood through the umbilical vessels. 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