Anatomical closure of ductus aeriosus gets completed by:
**Core Concept**
The anatomical closure of the ductus arteriosus is a critical process that occurs after birth, marking the transition from a fetal circulation to a postnatal circulation. This process involves the transformation of a patent ductus arteriosus into a ligamentous structure, known as the ligamentum arteriosum.
**Why the Correct Answer is Right**
The anatomical closure of the ductus arteriosus is primarily facilitated by the decrease in oxygen tension and the subsequent increase in prostaglandin E2 degradation. As the ductus arteriosus is exposed to higher oxygen levels after birth, the enzyme prostaglandin E2 synthase is deactivated, leading to a decrease in prostaglandin E2 production. This decrease in prostaglandin E2 levels causes the smooth muscle cells in the ductus arteriosus to contract, leading to its closure. The ductus arteriosus then undergoes fibrosis and eventually transforms into the ligamentum arteriosum.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the physiological process of ductus arteriosus closure.
**Option B:** This option is incorrect because it is not the primary mechanism responsible for ductus arteriosus closure.
**Option C:** This option is incorrect because it does not accurately describe the anatomical changes that occur during ductus arteriosus closure.
**Clinical Pearl / High-Yield Fact**
The ligamentum arteriosum, formed from the anatomical closure of the ductus arteriosus, can be a useful landmark for thoracic surgeons during lung transplantation. Its location can help guide the placement of the pulmonary artery anastomosis.
**Correct Answer: C.**