At what gestational week does the spleen begin to develop?

At what gestational week does the spleen begin to develop?

• A. 4th week
• B. 5th week
• C. 7th week
• D. 9th week

Answer: (C)

The spleen forms from mesenchymal tissue in the dorsal mesogastrium, part of the foregut derivatives, and its development is tied to the rotation of the stomach. The splenic primordia begin as condensations in that region, with early tissue recognizable around the end of the first trimester. By about the seventh week, these splenic primordia have coalesced into a distinct developing spleen with a nascent capsule and beginning vascular supply from the splenic artery. This is why the seventh week is the point at which spleen development is typically recognized as underway in many embryology timelines—the organ is becoming a clearly defined structure, even as growth and maturation continue in the following weeks.

The spleen forms from mesenchymal tissue in the dorsal mesogastrium, part of the foregut derivatives, and its development is tied to the rotation of the stomach. The splenic primordia begin as condensations in that region, with early tissue recognizable around the end of the first trimester. By about the seventh week, these splenic primordia have coalesced into a distinct developing spleen with a nascent capsule and beginning vascular supply from the splenic artery. This is why the seventh week is the point at which spleen development is typically recognized as underway in many embryology timelines—the organ is becoming a clearly defined structure, even as growth and maturation continue in the following weeks.