Erythropoetin in fetus is secreted by?
**Core Concept**
Erythropoietin is a hormone that plays a crucial role in the production of red blood cells. In adults, it is primarily produced by the **kidneys**, but its production site differs in the fetus. This hormone is essential for regulating **erythropoiesis**, the process by which red blood cells are produced.
**Why the Correct Answer is Right**
In the fetus, erythropoietin is secreted by the **liver**. This is because the fetal liver is the primary site of erythropoiesis during early gestation. The liver produces erythropoietin in response to hypoxia, stimulating the production of red blood cells. As the fetus develops, the kidneys start to take over this function, but in early fetal life, the liver is the main source of erythropoietin.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because while the kidneys do produce erythropoietin in adults, they are not the primary source in the fetus.
**Option B:** Incorrect as the spleen, although involved in filtering the blood and storing red blood cells, is not the primary source of erythropoietin in the fetus.
**Option D:** Incorrect because the bone marrow, while a key site for blood cell production, is not the primary source of erythropoietin in the fetus.
**Clinical Pearl / High-Yield Fact**
It's crucial to remember that erythropoietin production shifts from the liver to the kidneys as the fetus matures. This knowledge is vital for understanding fetal development and the regulation of red blood cell production.
**Correct Answer:** C. Liver.