Anatomical closure of ductus aeriosus occurs at ________
**Core Concept**
The **ductus arteriosus** is a fetal blood vessel that connects the **pulmonary artery** to the **aortic arch**, allowing blood to bypass the lungs. After birth, it normally closes due to increased oxygen levels. Anatomical closure refers to the permanent sealing of this vessel.
**Why the Correct Answer is Right**
Anatomical closure of the ductus arteriosus occurs within **10-14 days** after birth, as the smooth muscle in its wall constricts in response to increased oxygenation, leading to fibrosis and eventual permanent closure. This process is crucial for establishing the normal postnatal circulation pattern.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it's too early for anatomical closure.
**Option B:** Incorrect as it's not specific enough.
**Option D:** Incorrect because it's too late.
**Clinical Pearl / High-Yield Fact**
Remember, functional closure of the ductus arteriosus occurs soon after birth, but anatomical closure, which is permanent, takes a bit longer. This distinction is key in understanding neonatal circulation.
**Correct Answer:** D. 10-14 days