Common site of haematopoiesis in fetus is –
**Core Concept**
Haematopoiesis is the process of blood cell formation, which occurs in different sites at various stages of development. In the fetus, haematopoiesis shifts from the yolk sac to the liver and spleen before eventually moving to the bone marrow.
**Why the Correct Answer is Right**
In the fetus, the liver is the primary site of haematopoiesis from approximately 6-8 weeks of gestation until about 24 weeks. This is due to the presence of erythropoietin receptors on the surface of liver cells, which allows for the production of red blood cells. The liver's role in haematopoiesis is essential for the production of blood cells to meet the increasing oxygen demands of the fetus.
**Why Each Wrong Option is Incorrect**
* **Option A:** The yolk sac is the primary site of haematopoiesis in the early embryo, but it ceases to be a significant site of blood cell production after 8 weeks of gestation.
* **Option B:** The spleen does contribute to haematopoiesis in the fetus, but it is not the primary site. It plays a more significant role in filtering the blood and storing red blood cells.
* **Option C:** The bone marrow eventually becomes the primary site of haematopoiesis in the fetus, but this does not occur until after 24 weeks of gestation.
**Clinical Pearl / High-Yield Fact**
The liver's role in haematopoiesis in the fetus highlights the importance of liver function in overall fetal development and oxygenation.
**Correct Answer: C. Bone marrow**