All are of adult size at bih except:
**Core Concept**
The question is testing the knowledge of the development and growth of various organs and systems in the human body. Specifically, it's asking about the organs that are not fully developed or of adult size at birth.
**Why the Correct Answer is Right**
The pancreas is one of the organs that is not fully developed at birth. It continues to grow and mature after birth, with significant changes occurring during the first few years of life. This is in contrast to organs like the lungs, liver, and kidneys, which are relatively developed at birth. The pancreas's delayed development is necessary for its role in producing digestive enzymes and hormones like insulin, which become more crucial after birth.
**Why Each Wrong Option is Incorrect**
**Option A:** The lungs are actually relatively mature at birth, with the majority of their development occurring in utero. They are able to inflate and deflate, and the alveoli are formed and functional at birth.
**Option C:** The liver is also relatively mature at birth, with its main functions, such as detoxification and protein synthesis, being established during fetal development.
**Option D:** The kidneys are relatively mature at birth, with their main functions, such as filtration and electrolyte balance, being established during fetal development.
**Clinical Pearl / High-Yield Fact**
A classic exam trap to remember is that the pancreas is one of the organs that continues to grow and mature after birth, whereas organs like the lungs, liver, and kidneys are relatively developed at birth. This is an important concept for students to remember as it has implications for the management of various pediatric conditions.
**Correct Answer:** D.