Organogenesis take place in the first trimester. Which of the following structure attains adult size before bih?
**Core Concept**
Organogenesis refers to the process of formation and differentiation of organs from the embryonic tissues during embryonic development. It primarily occurs in the first trimester of pregnancy. However, some structures continue to grow and develop after birth, while others reach their adult size before birth.
**Why the Correct Answer is Right**
The structure that attains adult size before birth is the lung. The lungs start to produce surfactant, a substance that reduces surface tension in the alveoli, allowing them to expand and contract properly, around the 24th week of gestation. This is crucial for the baby to breathe after birth. The lungs continue to grow and mature until birth, when they reach adult size and are ready for independent gas exchange.
**Why Each Wrong Option is Incorrect**
* **Option A:** The pancreas is not fully developed before birth and continues to grow and mature after birth.
* **Option B:** The liver is partially developed before birth but continues to grow and mature after birth, especially during the first few years of life.
* **Option C:** The brain and spinal cord continue to develop and mature after birth, with significant growth occurring during childhood and adolescence.
**Clinical Pearl / High-Yield Fact**
Remember that the lungs are the only organ that reaches adult size before birth. This is crucial for the baby to breathe and survive after birth. Any issues with lung development or function can lead to respiratory distress syndrome, a common condition in premature infants.
**Correct Answer:** C. The lung.